As you can imagine, swelling in the jaw or throat region can influence how a horse accepts the bridle. When a swollen area is under compression or load, such as when we ask the horse to come onto the bit, we can experience all kinds of resistance, ranging from slightly stronger or weaker pressure on the bit to severe, adverse behaviors such as rearing, headshaking and pulling on the reins.

In all cases of a sudden change in contact, it is a good idea to carefully inspect the jaw and throat region. Ask your veterinarian for assistance and advice when you notice abnormalities or you run into clear contact or connection problems. The anatomy of the head, neck and jaw is complex, and with many different structures found in this region, it is important to determine, if possible, which specific structures are associated with the swelling. Lumps and bumps may result from direct trauma, indicate inflammation or may develop from the accumulation of tissue in a more chronic process. 

Evaluation of any bump begins with physically examining the area to determine the exact location and to check for wounds, skin irritation, heat or sensitivity. Palpation of the lump to determine its characteristics may help identify which tissues are involved. For example, bone will be hard. Additional diagnostic procedures, including radiographs (X-rays), ultrasound, endoscopy or even biopsy, may be necessary to get a complete clinical picture. 

While we can’t go over every cause for lumps under the jaw here, we can review the most common sources. These include swollen lymph nodes, reactive salivary glands and dental matters. 

Lymph Nodes

Horses have two major sets of lymph nodes located near the jaw: the submandibular lymph nodes, found between the mandibles (lower jawbones), and the retropharyngeal lymph nodes, situated near the throat. Lymph nodes are a part of the immune system and they become enlarged when they react to an ongoing process.

Localized infections, such as an abscessed tooth, are likely to result in enlargement of a single lymph node close to the site of infection. In contrast, respiratory illness may result in swelling of one or more nodes. Many viral infections will cause mild lymph-node enlargement that resolves in one to two weeks with no special treatment.

Streptococcus equi, also known as “strangles,” is a bacterial infection that can result in severe enlargement of the retropharyngeal lymph nodes. This type of swelling may be seen and felt just behind the mandible. 

Horses with strangles will run a fever and may develop thick nasal discharge. In some cases, the affected lymph nodes may become so enlarged that they put pressure on the horse’s airway.

Reactive Salivary Glands

Swelling of the salivary glands is commonly seen in horses turned out to pasture in the spring. The parotid glands are the largest salivary glands and are found on both sides of the head, extending from the jaw to the base of the ear. 

These glands produce saliva, and affected horses may drool excessively. A toxin produced by a fungus on clover is believed to be at the root of this reaction. This condition is usually not painful, but swelling may be significant enough to prevent the horse from flexing well at the poll. 

Simply avoiding pasture turnout for a few weeks usually remedies the problem. Rarely, the salivary glands become infected or develop blockages that can also result in swellings. You should seek advice if swellings in this area come up at other times of year or don’t resolve quickly.

Dental Matters

Teething bumps, or eruption cysts, are hard enlargements seen along the jawline in horses younger than 5 years of age. The bumps are caused by changes in the bone as the permanent premolar and molar teeth emerge and displace the deciduous, or “baby,” teeth. 

Several such swellings can usually be felt at the same time and are equal in size. They should not be painful or hot. Occasionally bumps may also be noted along the bridge of the nose as a similar process can occur with the upper teeth. In general, teething bumps are strictly cosmetic and should spontaneously resolve as the horse matures. 

Occasionally, teething bumps are an indication of problems in shedding of the deciduous teeth, commonly known as “retained caps.” An oral exam by a veterinarian or veterinary dentist can be helpful to determine if more significant dental problems exist.

Other causes of lumps near the jaw include local trauma resulting in soft- tissue injury and even fractures, insect bites and, very rarely, tumors. 

You should consult with your veterinarian about any new swelling that persists for more than a few days or any lumps that are enlarging, painful or located in areas that interfere with your tack or riding.

About Kimberly Johnston, VMD, Dipl. ACVS 

Kimberly Johnston, VMD, Dipl. ACVS, graduated from the University of Pennsylvania and New Bolton Center. She became a diplomate of the American College of Veterinary Surgeons in 2010, specializing in sports medicine and orthopedic surgery. In her free time, she enjoys riding her 14-year-old Thoroughbred, Jazz, schooling Third Level. She and her FEI-dressage-riding husband, Rob van Wessum, DVM, operate Equine All-Sports Medicine Center in Mason, Michigan. 

Being fine-tuned to his surroundings is part of your horse’s nature, and a keen sense of hearing is a big part of that. In this article, two experts shed light on how hearing helps horses make sense of his environment and how to handle hearing-related problems. Allison J. Stewart, BVSC, DACVIM, DACVECC, is a professor of equine internal medicine at Auburn University. Bonnie Beaver, DVM, focuses on animal behavior as a professor at Texas A&M University.

A horse’s hearing isn’t very different from yours, the experts say. You can detect sounds with wave frequencies from 20 hertz (lowest pitch) to 20,000 hertz (highest pitch); for horses, the range is 55 hertz to 33,500 hertz. “They can’t hear quite as low as we can and can hear just slightly higher,” Beaver says. Many animals, including dogs, hear higher-pitched sounds; many can hear lower.

But horses excel at capturing faint sounds that you may easily miss and honing in on the directions sounds come from. Their ears contain the same structures yours do, but differences in design enhance these abilities.

What Big Ears You Have

Those big ears make a big difference. With its large size and cupped shape, each outer ear (pinna) is like a radar dish, collecting and concentrating sound waves. You have to turn your head to focus on the source of a sound, but your horse has ten muscles that can rotate each pinna in a full 180-degree arc—and he can move them independently, so that one turns forward while the other aims back.

The pinna funnels sound waves into the ear canal, which amplifies them in the same way that talking into a tube amplifies sound. At the middle ear the sound waves strike the eardrum (tympanic membrane), making it vibrate. The vibrations travel through the membrane to the ossicles, three tiny bones on the far side. These bones—called the hammer, anvil and stirrup for their shapes—form a chain that transmits the vibrations to a second membrane, which marks the start of the inner ear.

The inner ear holds sensory organs for both hearing and balance. The cochlea is the hearing part. It’s shaped like a snail shell and filled with fluids that move as vibrations from the membrane travel through them. The movement stimulates tiny hair cells (cilia) that send nerve signals to the brain. Different hair cells are sensitive to different sound frequencies.

Inner-ear fluid also circulates through the semicircular canals, which help the horse stay steady on his feet and in balance. The canals are lined with sensory hair cells and set at different angles, so they detect different movements—side-to-side, up-and-down, angled.

Run First, Ask Later

A twig snaps and your horse is off like a shot. His hair-trigger reactions are nerve-wracking when you’re riding or handling him, but they developed as a defense against predators. Back when his ancestors were wild, horses that didn’t run when a twig snapped were likely to be dinner for lions. Those that took off survived, and over generations that quick flight response became hardwired.

All horses share the basic response, but reactions to sudden sounds vary from one horse to the next. When a pebble hits the arena wall, one horse may spook 10 feet sideways while another barely alters his stride. Genetics and experience account for the differences, Beaver says. “Some individuals are ‘spookier,’ and that can have a genetic basis. Other individuals have not had experiences that would expose them to different environments that contain noise, so they may overreact,” she says. “We haven’t done enough hearing tests to know if there are differences in sensitivity to sound. If there are, they are probably minor.”

“The best way to deal with these episodes is to stay calm and guide the horse away from the perceived danger,” she adds. “A calm, consistent rider is best for horses that tend to react, so that they learn to trust the rider.” Punishing a horse for spooking will only reinforce his fear.

Exposing the horse to sounds in non-frightening situations is the best way to teach him to accept them, Beaver adds. The techniques of desensitization and counter-conditioning can help. In desensitization, the horse is exposed to the sound when he’s in a safe and familiar environment. (Think of Anna Sewell’s Black Beauty, who was pastured next to railroad tracks so he would learn to accept the terrifying sight and sound of trains.) In counter-conditioning you reward the horse while he’s exposed to the scary sound, typically with treats like carrot bits or feed pellets, so he comes to associate the sound with something pleasant. In both techniques it’s important to start with short sessions and low noise levels, increasing only as he tolerates the sound.

“Horses tend to respond to sounds separately,” Beaver says, so don’t assume that your horse will apply what he learns to new situations. He may realize that the sound of a tractor grooming the arena is not a threat, but that doesn’t mean he’ll accept the sound of a tractor-trailer coming up behind him on the road.

Cotton or equine earplugs can muffle sounds when sudden noises may be a problem—when construction is going on nearby, say, or in a snow-covered indoor arena where ice may abruptly slide off the roof. (Check the governing rules for your discipline before using earplugs in competition, though. They’re not allowed in dressage.)

Even with earplugs, some horses are so freaked out by loud sounds such as thunder and fireworks that they can injure themselves (or you) in their panic. When storms move in (or July 4 rolls around) these horses are safest in their stalls.

Hearing Loss

It’s likely that many horses lose some hearing ability with age, Stewart says, although this is something that hasn’t been widely tested. Researchers in Australia recently compared hearing ability in two groups of horses, ages 5 to 8 and ages 17 to 22, and found mild to moderate losses in the older group. (The researchers used brainstem auditory evoked response, or BAER, testing, in which electrodes attached to the skin of the horse’s head monitor the brain’s response to clicking sounds.) People also hear less well as they age—a lifetime of exposure to noise takes a toll on the sensory receptors in the inner ear. Beaver says that horses may suffer less loss than people do. “Horses don’t live as long or in the same environments [think rock concerts and iPods] as humans,” she notes. Day to day, you probably won’t notice mild hearing loss in your horse.

Deafness is rare in horses. It can be ruled out by electronic testing or simply by checking the horse’s reaction to a sudden noise, like clapping your hands or dropping a bucket. The sound should prompt a startle reaction—at minimum, a twitch of an ear. If the horse shows no response at all, he probably can’t hear it.

A congenital form of deafness occurs in some horses with “splashed white” coat patterns, Stewart says. A splashed white horse has an extremely wide blaze or “bald” face, often with blue eyes, and variable white markings on the legs and body. Some of these horses are born deaf. Researchers have identified three separate genetic mutations that can produce the pattern. Two turned up only in Paints and Quarter Horses, and the third appeared in those breeds as well as in Morgans, Trakehners and a few other breeds.

Splashed white horses have white faces and blue eyes because, during development, their genes suppress pigment-producing cells called melanocytes. If the lack of pigment extends into the inner ear, it affects the sound-sensitive hair cells and leads to deafness, Stewart says. Not all white markings come with the same risk of deafness, and horses can be tested for the splashed white mutations. (The University of California, Davis, offers a test.)

Hearing should be tested as part of a pre-purchase exam, Stewart says. But, she notes, deafness isn’t a huge handicap for a horse. Because a deaf horse doesn’t hear what’s going on around him, he obviously won’t spook at sounds—but he may spook if something suddenly touches him or pops into view without warning. “It’s usually not a problem if you don’t sneak up behind the horse,” she says.

Beaver agrees. “Hearing is often a first or second alert system for potential predators, and that isn’t much of a factor for most horses today,” she says. You may need to modify your aids, she adds—“obviously things like ‘whoa’ won’t work”—but most deaf horses adapt well. Many have had successful show careers.

Pinna Problems

The most common ear conditions in horses are ones you can see—skin problems that affect the pinna.

Fly bites. Black flies and other biting flies love horses’ ears, and the bite sites can become inflamed, crusty, itchy and sometimes infected. Use a topical antibiotic ointment to help control infection while the bites heal. Keep the flies away by using repellents, a fly mask with ear covers for turnout and an ear bonnet when you ride. Avoid clipping the ears unless you must do so to treat an infection—the hair helps protect the skin from bites.

Aural plaques. Aural plaques are flat, scaly, whitish growths on the inside (concave) surface of the pinna. They’re caused by papilloma viruses that are often spread by biting black flies. “Ignore them,” Stewart says. Although the plaques don’t look pretty, they do no harm to the horse. Attempts to remove them typically cause so much discomfort that the horse becomes sensitive about having his ears handled. Use the steps above to prevent black flies from getting to the ears. These flies are most active around dawn and dusk, so keep the horse in at those times.

Sarcoids. The ears are a prime spot for these common skin tumors, Stewart says. Sarcoids are not malignant but can grow aggressively. They can appear as hairless, scaly areas; hard bumps under the skin; or warty or fleshy growths. Some become raw and irritated, and some grow massive and cauliflower-like. It’s thought that infection with bovine papilloma virus, the cause of warts in cattle, may trigger the growths.

“Sarcoids are unsightly, but we generally leave them alone unless they are so large that they cause a problem for the horse,” Stewart says. There are many different treatments—surgery, cryotherapy (freezing), chemotherapy, radiation and more—but none is a sure bet, and the tumors tend to grow back. “Treatment overall has a 70 percent success rate. You may need to retreat several times,” she says. “The horse may come to vigorously resent having his ears handled, and the ear can be disfigured.”

So far no one has found a way to prevent sarcoids. Good fly control may help, however, as flies can spread the virus. Treatment with the chemotherapeutic drug cisplatin seems to slow the regrowth of these tumors. The drug is injected or released by implanted beads.

Deep Trouble

If a horse has a problem deeper in the ear, he may shake his head or hold the affected ear at an odd angle, tipped down to the side, because it’s irritated. He may also object to having the ear handled, but this isn’t a reliable sign. “Ears are sensitive and are naturally something to be protected. If the horse has also had a painful experience or been mishandled, especially while being clipped, it can aggravate the avoidance behavior,” Beaver says.

Ask your veterinarian to examine the ear. Stewart says it’s difficult to see into the ear canal even with an otoscope, the device used in many other animals as well as people, because the horse’s canal has a 90-degree bend. The vet can get a better look using a small flexible endoscope. The exam might discover:

Ticks. Ticks can attack the ear canal as well as the pinna. A type of tick found in the Southwest, the spinous ear tick, is especially known for this; infestation with these ticks can cause pain, inflammation and sometimes even muscle spasms. The horse will need to be heavily sedated for the ticks to be located and removed.

Mites: These tiny tick relatives can also get into the ear canal, although they are less common in horses than in some other animals. Deworming with ivermectin can help control them.

Infection: Ear-canal infections of the sort that plague dogs and cats are very rare in horses. “I haven’t seen one in 20 years. In a small animal practice, you’d expect to see one every day,” Stewart says. Bacterial infections can result from tick infestation, though. They are treated with topical and systemic medications.

Middle-ear infections are also extremely rare in horses, but they occur. Infection can spread from the respiratory system by way of the Eustachian tubes, which link the middle ear to the pharynx, or the guttural pouches, which open off the Eustachian tubes. It can also reach the middle ear from the outer ear canal or through the blood. These infections are treated with systemic antibiotics.

Ear Talk

Horses use body language to communicate with each other. Head and body positions, facial expressions and tail action all speak volumes. But for a quick read on what a horse is thinking, just look at his ears.

Ears held loosely to the side: “Just chillin’.” He’s relaxed.

Ears pricked forward: “What’s up?” If what he hears is really interesting (or alarming), he turns to face the sound and freezes in place.

Ears back: “I don’t like this.” He may be worried, fearful or feeling discomfort.

Ears pinned flat back: “Get out of my space!” He means business.

Ears shifting forward and back: “Lots going on here.” Constant motion is the default mode for a horse’s ears, helping him keep tabs on his surroundings. Rapid flicking can suggest nervousness; you’ll often see this when a horse is in a new environment with unfamiliar noises.

One ear back: “I’m listening.” He may be focusing on his rider or a horse approaching from behind with one ear, but he’s still scanning his surroundings with the other.

Ears drooping: “Tuned out.” Ears may droop when a horse is dozing, doped or sick. This can also be a sign of submission.

For More:

• Read more about how to protect your horse from ticks here.
• Learn how to beef up your fly-control program to prevent flies from driving your horse (including his ears) crazy this summer here.

This article originally appeared in the November 2014 issue of Practical Horseman.

     ~ Johnna L., New Mexico

A: A tight girth can certainly be uncomfortable for your horse and can interfere with performance, especially in sports that require a high level of cardiovascular fitness. During exercise, your horse’s chest expands every time he inhales. The faster he moves, the more his chest must expand because he needs to get more oxygen to his working muscles. A too-tight girth can limit this function.

In some horses, an overtightened girth can also pull the saddle forward. We call the area in front of the expanded part of the horse’s chest “the girth line.” Because of the girth line’s smaller circumference, the girth tends to migrate to it, no matter where you position the girth. In horses whose girth line is situated far forward—just behind their elbows—the girth will tend to slide forward.

If the billet straps are being pulled forward by the girth rather than hanging vertically, the saddle will likely be pulled forward onto the horse’s shoulders, especially if the girth is overtightened. A differently constructed saddle with a point billet that is situated further forward may be helpful in these horses.

Secure, But Not Too Tight

Studies show that girth tension increases as a horse breathes in and decreases as he breathes out, with the highest girth tensions being recorded during galloping. Scientists measure tension in the girth in newtons, but since most of us don’t know what a newton feels like, I’ll make a rough conversion into pounds. If the girth is tightened to 22 pounds when the horse is at rest, the girth tension during inspiration (breathing in) when he’s galloping increases to around 48 pounds. This may reduce the expansion of his rib cage and interfere with his work capacity.

It is recommended, therefore, that girth tightness be no more than 22 pounds when the horse is standing still. At this tightness the girth will be snug against your horse’s body but you will still be able to slide three fingers underneath it.

The challenge is to get the girth tight enough to hold your saddle securely in place without making it so tight that it interferes with your horse’s mechanics or pulls the saddle forward. There is no hard, fast rule for this. The shape of your horse’s back plays a role; generally horses with well-defined withers stabilize the saddle better, so they require a less tight girth than those with more rounded withers.

The design of the saddle is also a factor, especially the length of the tree points and the vertical parts of the flaps, which help to stabilize the saddle. Longer tree points and flaps tend to be more stable, but make sure they are not restricting the movements of the shoulder. A well-balanced rider has a stabilizing effect on the saddle, too, whereas a poorly balanced rider may allow the saddle to slip to the outside on turns.

Girth Size and Type Can Be a Factor

The size and type of your girth can be influential as well. When choosing a girth, evaluate its position and the position of the buckles on your horse’s chest. The highest pressure under the girth occurs just behind his elbow. Avoid using a girth that fits closely behind the elbow.  Consider buying a girth that is contoured in this area (designed so it curves away from the elbows). When using a contoured girth, make sure it is the correct size and attached to the saddle billets evenly on both sides, so that the parts that are cut back are at the level of your horse’s elbows.

In racehorses, the use of a girth that is elastic throughout its entire length has been proven to give some protection against over-tightening. A girth that is elasticated only at the ends is unlikely to offer similar protection, although it does offer some room for expansion provided the girth is not adjusted so tightly that the elastic is fully stretched.

When you tack up your horse, attach the girth loosely at first, then tighten it gradually before mounting. After a few minutes in the saddle, it’s usually possible to tighten the girth a little more because your fluffy saddle pad has flattened down and, if your horse puffed himself up when the saddle was being put on, he will have unpuffed after being ridden for a short time. Be careful not to shift your weight in the saddle when adjusting your girth while mounted, as this can pull the saddle out of place.

Key Takeaways

To get an idea of how tight your particular girth needs to be given all the variables I mentioned above, check the position of your saddle now and then throughout your ride. If it tends to slip to one side or backward toward your horse’s tail, the girth may need to be a hole tighter. On the other hand, if your saddle never budges, try the girth a hole looser. Make these adjustments gradually and never risk riding with a girth so loose that the saddle might shift dramatically and jeopardize your safety.

For tips on saddle fit and to learn about new research on the importance of assessing saddle fit while your horse is motion, click here.

About Hilary Clayton

Hilary Clayton, BVMS, PhD, DACVSMR, MRCVS, is a leading expert in equine biomechanics who has transformed the sporthorse world’s understanding of the performance and soundness of equine athletes. She grew up in England and earned her veterinary degree from Glasgow University before going on to research and teach at veterinary colleges in the United Kingdom, the Netherlands, Canada and the U.S. From 1997 to 2014, she served as the Mary Anne McPhail Chair in Equine Sports Medicine at Michigan State University’s College of Veterinary Medicine. Her work has included studies of bitting, saddle-fit biometrics, kinematics and conditioning, with an emphasis on the prevention and treatment of lameness. Also an experienced eventer, show jumper and dressage rider, Dr. Clayton is a U.S. Dressage Federation bronze, silver and gold medalist and a certified equestrian coach in the U.K. and Canada.

This article originally appeared in the November 2015 issue of Practical Horseman.

That’s the bottom-line finding of research led by Rachel Murray, VetMB, MS, PhD, MRCVS, Dip ACVS, associate of European College of Veterinary Diagnostic Imaging, who works at England’s Animal Health Trust. Specifically, Murray and colleagues compared pressure, limb protraction, knee and hock flexion, and back width between saddles fitted to industry guidelines and one specially designed to reduce pressure along either side of the thoracic vertebrae known as T10 to T13. (Previous research had shown that a horse’s back, or thoracolumbar, width increases after exercise when his saddle fits properly as well as when horses are ridden more correctly with a more skilled rider.)

The study included 13 international-level dressage horses, aged 8 to 16 years, with no existing lameness or performance problems. They were each ridden in the study by their usual professional riders. For the control portion of the test, they were ridden in their normal saddles, which were evaluated and fitted by four qualified saddle fitters.

The test saddles had modifications over typical saddles. The tree shape, alignment of the girth billets and shape of the panels were adjusted to accommodate the horse’s musculature (thoracolumbar expansion) during exercise versus while standing. The solid arm of the panel was shortened to reduce the area of potential restriction at the front of the saddle and the stirrup bars were attached to the exterior of the tree. The panels were lined with pressure-absorbing material.

Researchers used a pressure mat under the saddle panels as well as high-speed motion capture to evaluate the effect of the two saddles on the horses while being ridden at sitting trot. In addition, the thoracolumbar width was measured before and after exercise.

The researchers found that peak pressures were significantly less with the test saddles than the control saddles. In addition, the test saddles allowed greater limb protraction as well as greater knee and hock flexion. The post-exercise thoracolumbar width was also significantly greater with the test saddles.

Murray explains that the most significant takeaway from the study is the understanding that when a horse works correctly, his back expands under the saddle. “If the saddle does not allow this expansion/lift, the horse will be discouraged from working correctly and encouraged to work with a hollow, potentially dipped back, which can affect the movement of the forelimbs and hind limbs as well as restrict back movement,” she says.

Standard saddle-fitting guidelines don’t necessarily take this into account. Therefore, she adds, it’s important to assess saddle fit not simply when the horse is standing still, but also during exercise.

This article was originally published in the October 2017 issue of Practical Horseman. 

“DSLD is seen in the suspensory ligament—a degeneration of the ligament itself,” says Sabrina Brounts, DVM, MS, PhD, professor of Large Animal Surgery at the University of Wisconsin-Madison, School of Veterinary Medicine.

The suspensory ligament starts just below the knee in a horse’s front legs and the hock in the hind legs. It runs down the back of a horse’s cannon bone—the bone from the knee or hock to the fetlock—between the splint bones. About halfway down the length of the cannon bone, the suspensory ligament splits into two branches that continue down and then pass around the back of the ankle—the fetlock joint—and end on the front of the long pastern bone below. Its job is to support the fetlock as it sinks under weight and returns to normal when the weight comes off.

In a horse with DSLD, leg conformation gradually changes; gradual rupture of the suspensory ligament tissue allows the fetlock to drop. “The pastern becomes more horizontal and parallel to the ground and less upright,” Brounts says. “When the fetlock drops, it changes the angles of the hocks and stifles, giving the leg a straighter appearance.”

Jaroslava Halper, MD, PhD, a professor in the Department of Pathology, College of Veterinary Medicine, University of Georgia, adds, “DSLD is not well defined but affects mostly tendons and ligaments, which are connective tissue. It affects the fetlocks and suspensory ligaments when the horse puts weight on the leg, creating stress and pressure.

“This problem seems to run in certain families and bloodlines, but we have not yet identified the genetic component that results in these changes,” Halper continues. “There are more cases being diagnosed now than in earlier years, but I don’t know if it’s become more prevalent or if people are noticing it more today because they are more aware of it.”

Signs and Diagnosis

There are several reasons for suspensory problems, especially in sporthorses like warmbloods or horses who compete in dressage, jumping and eventing. They can twist an ankle or overstretch a ligament, for instance. With DSLD, the horse starts to get a little stiff, but he “usually has no history of trauma, no previous injury or anything a person could pinpoint as a cause,” Brounts says. “This is the classic picture of DSLD; it just gradually develops.”

Another indication as to whether a horse has DSLD is to determine whether it’s just one leg versus multiple legs. “With DSLD, usually more than one leg is affected. In most cases, it’s both hind legs,” Brounts says. “If it’s just one leg, it’s probably not DSLD, but you should still evaluate all legs since one side can be more severe (and more painful) than the other.”

Horses affected by DSLD may shift weight back and forth on the hind legs or be more comfortable on one than the other. These horses might not like having a foot picked up and don’t want to hold it up very long for the farrier or to have the foot cleaned—they don’t want to stand on one foot very long.

The lameness that develops gets worse over time. There may be swelling or thickening of the suspensory branches around the fetlock and pastern area and scar tissue develops around those branches. “Owners might mistake this for windpuffs, but windpuffs are associated with the fetlock joint. With DSLD, the suspensory ligament in the fetlock region is affected, outside the joint,” Brounts explains.

More Diagnosis

In a horse with DSLD, the suspensory ligament’s collagen fibers are disrupted. These fibers are made up of proteins that provide strength and structure to the body’s connective tissues. Normally, proteoglycans (large molecules of proteins and carbohydrates) “are very complex molecules that are important for the collagen to assemble properly in the tendon or ligament,” Halper says. But “if there is too much [proteoglycan], the tendon is not as strong as it should be. Sometimes the proteoglycans become cartilage.” Cartilage is weaker than collagen, and it does not stretch and bend, so as this tissue accumulates in the tendons and ligaments, these structures become progressively weaker, and the fetlock drops toward the ground.

The problem may appear at different ages in different horses but most commonly becomes obvious between 7 and 13 years old. It rarely starts in horses older than 15.

“It’s easy to detect accumulated proteoglycans and damaged collagen fibers with a post-mortem examination, but that won’t help the horse,” adds Halper. Instead, in addition to getting the horse’s medical history, a veterinarian will examine the legs and palpate the tendons and ligaments to detect thickening of the area. 

Halper also noted that some horses with DSLD also have changes in the arteries and skin. “I’ve found that the easiest thing to do is a skin biopsy to see changes in expression of certain genes,” she says. “We published a paper last year describing what we found—that these genes are more expressed in horses with DSLD.” (See “The Role of Genetics,” below). 

Another method of diagnosis is ultrasound, says Brounts. “Ultrasound of the whole suspensory ligament can help with diagnosis, especially in the fetlock area since that is where we see most of the changes,” she says. “If there’s a chance the horse may have DSLD, have an ultrasound done. If an injury doesn’t heal or a lameness doesn’t improve or gets worse over time, then you have an initial exam as a baseline for comparison later.”

Environment and Management

Progression of DSLD is unpredictable. “I’ve had some horses that took 10 years to finally get to an end point, and other horses had to be put down within just one or two years after the disease was diagnosed,” Brounts says. “We don’t know why DSLD develops quicker in some horses than others, but I think the environment comes into play.” Some of those factors may have more impact on certain horses.

“In the Peruvian Horse, we know heritability of DSLD is approximately 25%,” Brounts says. “This means that 25% of the risk of developing DSLD is genetic and the remaining 75% of the risk is attributed to environmental risks, such as the environment the horse grows up in.” 

She adds, “A human example might be a person with risk of getting lung cancer, increasing that risk if they smoke.” There are multiple factors, such as moderate heritability that influence DSLD. The health management in high-risk horses should be focused on modifying environmental risk factors so the likelihood of DSLD development is minimized in those horses.

“Every horse owner who participates in our research fills out a long questionnaire,” Brounts says. “We ask about everything—what the horse eats, what it does for work and how often, the shoeing, any medication and what age it started in training. These things are important because some of them might make a difference.” 

Risk factors may include physical activity and diet, for instance. “Maybe if we know we have a horse with increased risk, we shouldn’t start riding it as a 2- or 3-year-old; maybe we should start at 4 or 5,” Brounts says. “Or we should change something in their diet; less grain, or less fat or starch. We hope to discover environmental risk factors that we can modify for a horse that is high risk for DSLD. We can then make recommendations, so the environment and management becomes more favorable for that horse, and it might have less risk of manifesting DSLD.”

Treatment for DSLD

For affected horses, treatment needs to focus on easing pain and discomfort and this may vary from horse to horse. “Every horse presents at a different stage. We can’t cure the disease but can try to slow it down or at least make the horse comfortable. Common treatments include phenylbutazone (bute) or flunixin meglumine (Banamine^®) and supportive boots or wraps for the lower legs,” Brounts says.

Some horse owners use methylsulfonylmethane, glucosamine, polysulfated glycosaminoglycan (Adequan^®), etc. to try to aid the health of connective tissue. “Special/corrective shoeing to give the limb more support may also help. Other treatments that may help ease pain include laser therapy, shock wave, magnetic therapy, acupuncture, etc.,” she says.

Some owners investigate regenerative medicine like stem cell treatment and platelet-rich plasma. “These therapies can be helpful for tendon and ligament injuries, but DSLD is a progressive degenerative disease. Treatments might delay the inevitable process but are still experimental for horses with DSLD,” Brounts says.

A research group at Louisiana State University looked at the effect of exercise and athletic conditioning. Exercise didn’t seem to exacerbate the disease and helped horses with comfort. “We’ve learned that not exercising the horse at all is not wise in mild or moderate cases. Research showed that moderate exercise—like 30 minutes three times a week—can be helpful, if it’s not in deep footing or strenuous,” Brounts says.

The Future

“Once a horse is no longer comfortable and in a lot of pain, a tough decision must be made,” Brounts says. “This point may be different for each owner. Some make that decision sooner than others. This is a personal decision; the horse is part of the family and saying goodbye can be a process rather than an instant decision.” Information about DSLD may help an owner make an informed decision.

There is no cure; DSLD is a progressive degeneration and decline. “The only way we can prevent it is if we can find some changes with various tests,” explains Halper. “Then we won’t breed those horses.”

The Role of Genetics in DSLD

The best way to prevent future cases of degenerative suspensory ligament desmitis is to avoid the condition by investigating a horse’s genetic history and to have a thorough examination performed by a veterinarian. This might influence the decision of the owner regarding whether to breed that horse. 

“Our research can hopefully help owners decide what to do with an affected horse or a horse with increased risk,” says Sabrina Brounts, DVM, MS, PhD, professor of Large Animal Surgery at the University of Wisconsin-Madison, School of Veterinary Medicine. 

The challenge is that DSLD is known as a complex polygenic disease. “Most genetic diseases and screening tests in horses have been simple diseases, however,” Brounts says. “This means that a DNA mutation can result in a horse having the disease or being a carrier, depending on the mode of inheritance [dominant or recessive].”

DSLD is not as simple as a single dominant or recessive gene. “We were hoping it would be, but it’s not. It is the result of multiple genetic variations in the animal’s genetic material, in addition to environmental risk factors that have an influence,” Brounts says.

“We have collected [skin] biopsies from horses with DSLD and did some sequencing of the RNA [ribonucleic acid, which executes the instructions of DNA],” says Jaroslava Halper, MD, PhD, a professor in the Department of Pathology, College of Veterinary Medicine, University of Georgia. “We found changes in so many genes [more than 1,500]. Some are overexpressed or more active and some are underexpressed or less active than normal. Even though we didn’t have a lot of horses to test, these findings were pretty consistent.” The research showed that these genes are more expressed in horses with DSLD.

Halper hopes to expand her research on DSLD and “add more horses to the study, some with DSLD and some without it, and also horses that have skin diseases and horses with other tendon problems besides DSLD,” she says. “We would like to see if this approach could be more specific for DSLD than for other skin diseases or other musculoskeletal problems. Eventually we might have a test that could be commercially available to owners and veterinarians,” she says.

Selective breeding and identification of affected horses and horses at risk will be needed to help reduce cases. “The more horses we can test, the more we will learn. Some horses that appear to be normal can still have these changes,” Halper says.

“We try to help owners with our research, so they can make an educated decision. We’d like to continue our research in other breeds since a genetic component could also be present,” Brounts says. 

“We hope to make a connection with the human side,” she continues. “There is a type of tendon degeneration that occurs in people that is similar to DSLD [tendinopathy of the Achilles tendon in the human ankle]. Maybe the horse can be a model for human research and both species can benefit.”

One Owner’s Experience with DSLD

Karen Adams is a retired U.S. Equestrian Federation “R” dressage judge, instructor and coach in Keedysville, Maryland, and has had experience with degenerative suspensory ligament desmitis in a horse named Cordova (“Wild Bill”). 

Bill was the product of a test breeding between a Swedish stallion and a mare that was a mix of Mecklenburger (a warmblood type bred in the Mecklenburg-Vorpommern region of northeastern Germany), Thoroughbred and Paso Fino. At that time in the late 1980s, stallions had to be bred to test mares to make sure they weren’t carrying contagious equine metritis. “He had a huge, lofty trot, and a big, uphill, rolling canter but was oversized for his age,” she says.

Bill, who grew to about 17 hands before he was 3 years old, ended up with three problems: He was operated on before he was 2 years old with osteochondritis dissecans lesions in both hocks. When Adams started riding him when he was nearly 5, she discovered he was a roarer. “I wanted to make him into a competitive dressage horse, but with the hock issue I decided to just ride him for fun—teach him the exercises but not overly demanding work,” Adams said. 

In Bill’s early teen years, Adams noticed that occasionally his left hind ankle would swell a bit and look puffy. “Sometimes when I dismounted, one or both of his hind legs would quiver a little. … His left ankle began to sink lower to the ground,” Adams says.

She took him to an equine clinic in Maryland for a diagnosis. The vet there did several tests on his hind legs, and Bill was diagnosed with desmitis. The vet used shock wave laser treatments to strengthen the tissue.

Then Bill had a couple episodes becoming stuck in his stall, unable to get up. “This was scary, but he was still very sound. I just made sure he got turned out at night so he had plenty of room if he had trouble trying to get up, and made sure he was ridden by me or someone else who didn’t demand too much of his hind legs. I could do leg-yields and shoulder-in but didn’t try to do much that required pushing off with the hind legs,” she says.

Bill stayed sound until he was about 20 years old. Then his vet put him on a daily prescription nonsteroidal anti-inflammatory, which helped to ease discomfort. 

One day in August 2013, when Bill was 25, Adams got a call from the barn where he was boarded. “It was really hot, and Bill didn’t want to get up out in his pasture. I rushed out there and the vet came immediately, but none of us could get him up. We tried hosing him and a variety of things but he wouldn’t get up. I don’t know if he didn’t have the strength, or maybe something had torn loose, or maybe he just didn’t have the heart to try, so we put him down.”

Adams is not sure where DSLD came from in Bill’s bloodlines. She suspects that back before much was known about DSLD, she knew three Swedish warmbloods, including Bill, that had the condition. “I think big, large-jointed horses are probably more susceptible to many kinds of leg problems. With my horse Bill, there’s no way to know if it was his one-eighth Paso Fino blood or if the Swedish half contributed. It’s a degenerative disease that takes a long time to become evident,” she says.

“With Bill, it started with that puffy ankle. In some of my old photos of him I can tell that the left ankle is a little bigger, and also lower. With DSLD the deterioration is gradual and until you see the symptoms you wouldn’t suspect it,” Adams says. 

Fore More:

Learn how to manage other common sport horse injuries here.

This article was originally published in the Fall 2024 Issue of Practical Horseman Magazine.

However, the SI joint is different from other joints, such as the fetlocks or the hocks, in that it has relatively little actual motion itself, has no specific joint capsule, has very little associated joint fluid and is composed of two different types of cartilage. Stability of the SI joint is achieved by a complex ligamentous structure and associated muscles. 

Unfortunately, this important and intricate joint is very difficult to evaluate. Due to its location deep in the pelvis and its protection by thick muscles and fat, the equine SI joint is not possible to see or easily palpate (physically touch or manipulate). The size and density of that part of the horse’s body make it hard to obtain conventional radiographs, and ultrasound imaging can also be challenging. The clinical complaints and signs of potential SI problems can also be caused by any number of other issues and conditions in the horse. Consequently, identifying and accurately diagnosing equine SI problems is a significant challenge for horse owners and their veterinarians.

But understanding how important the SI joint is to the horse’s basic motion and knowing the early signs of problems are the first steps to getting a diagnosis and establishing a pathway back to health.

Signs of Potential SI Issues

All the motions that we ask performance horses to do require a functioning SI joint. These include running at speed, quick stops and tight turns, jumping, lead changes and gymnastic movements. Problems or issues with the SI joint can result in any number of vague motion-related problems. Often riders report feeling or sensing problems that are not visible as a true “lameness” when the horse’s motion is observed. These can include:

• A recent and progressive unwillingness to work with a loss of normal forward motion or impulsion.
• Resistance to collection or rounding through the back. 
• Tightness and stiffness, especially in transitions. 

Additionally, affected horses may begin to have trouble with lead changes, refuse jumps or even begin to buck and kick out. 

Other observations include:

• A mild dragging of one or both hind limbs.
• Asymmetry of the hind end or uneven pelvic motion and muscle development in more long-standing cases. 
• Abnormal tail carriage or unequal tracking of the hind legs especially on a circle. 
• Alterations of a fluid, rhythmic canter.
• A “bunny-hopping” motion of the hind legs. 

It also is always advisable to ask the farrier whether there have been any subtle changes in the horse’s behavior while being shod. Occasionally, very early SI changes are noted by the farrier as the horse may not move over easily when cross-tied and asked to step laterally. Or the horse may have more trouble balancing on a hind leg when the opposite hind is lifted and manipulated by the farrier. 

Since SI issues can be subtle and hard to definitively diagnose, all these seemingly small complaints should be treated with importance. If any of these signs are noted, then a diagnosis of a potential SI problem is justified. But because these signs can also be caused by a number of other conditions, it is important that a complete clinical examination and history be performed on affected horses. 

Diagnosing SI Issues

One category of SI problems can be considered acute. Acute or very recent development of SI-related clinical signs is likely to be trauma-related. Slipping on wet or uneven footing, falling while engaged in “pasture play” or in competition, kicking out or other forceful movements can all cause damage to the ligaments and muscles supporting the SI joint. If the trauma is severe enough, then the joint surface itself can be affected. A thorough history, paying attention to the condition’s timeline, will often reveal a likely underlying traumatic event. 

Another category of SI problems involves a chronic, more subtle, slowly progressing version. Dr. Sue Dyson of the Center of Equine Studies, Animal Health Trust, New Market, United Kingdom, published a review in the Equine Veterinary Journal in 2010 of 74 horses with diagnosed SI pain. Her finding showed that dressage and show-jumping horses appeared to be at greater risk for SI problems than horses used in other disciplines. Older horses, larger horses and heavier horses were also more highly represented, suggesting that “wear-and-tear”inflammation and stress on the SI joint due to long-term use and the demands on the body from a large, heavy frame resulted in more problems. Not surprisingly, warmbloods made up a higher proportion (51%) of affected horses compared to other breeds. Another important aspect of Dr. Dyson’s study was the finding that SI joint pain was seen alone in only 47% of the horses in her study group. Many horses had other problems or issues in other locations that were believed to be contributing to their SI problems. 

Weakness, unevenness or pain in other joints, muscles, ligaments or tendons will affect how the horse moves over time. Because of its location and purpose, the SI joint will be put under increased stress when the horse attempts to compensate for issues like these. 

Dr. Randy Eggleston, clinical professor and surgeon in the Department of Large Animal Medicine, Surgery and Lameness Service of the University of Georgia College of Veterinary Medicine, agrees that many SI problems stem from other issues in the horse. “While the sacroiliac joint has begun to receive much more attention recently and has almost become a trendy ‘popular’ diagnosis, the majority of suspected SI cases seen in our hospital have problems in other areas,” said Dr. Eggleston. 

Careful clinical evaluation of all these potential problems must be done first, according to Dr. Eggleston, and attention to and resolution of these issues often results in the elimination of SI pain. (See sidebar, “Underlying Conditions Contributing to Sacroiliac Issues,” below.)

Diagnosing Primary SI Issues

If no other physical problems are found on clinical examination, then a potential diagnosis of a primary SI condition should be considered and other specific diagnostic tests need to be done. Ultrasound examination of the SI joint is the most commonly used diagnostic procedure and can show evidence of degenerative disease (arthritis) of the joint or can indicate scarring and damage of the supporting soft-tissue structures. Large, heavily muscled horses can be difficult to scan due to the thickness of this area.

Transrectal ultrasound, where the ultrasound probe is inserted rectally, just as when a mare is scanned for pregnancy, may provide an additional “look” at the ventral (bottom) surface of the SI joint and can occasionally provide additional information. 

Radiography of the horse’s pelvis and SI is especially problematic due to both the size and thickness of that area. Conventional X-rays of the pelvis must be taken with the horse anesthetized and lying on his back. This positioning can sometimes allow a film to be taken, which may provide some useful information, but it is not always productive due to the horse’s challenging pelvic anatomy. Many veterinarians are sometimes reluctant to try radiography on these cases because of the stress of anesthesia induction and recovery. This stress can be especially difficult on horses that may already have pelvic instability and problems with their SI joints. 

Thermography, or infrared imaging, can be useful in identifying areas of inflammation or overuse in the SI region. Scanning the horse, then working the horse and rescanning, is especially helpful. This kinetic thermography can show a “before-and-after” change in blood flow and heat to a specific SI area and help confirm a diagnosis of SI injury. Dynamic diagnostic capabilities, or the modalities that can show the current physiological state of structures, are very important in confirming SI injuries because, as Dr. Eggleston explained, “We may see changes to the SI joint or surrounding structures with ultrasound and even radiography, but that doesn’t prove that those changes are significant in that particular horse or that they are even contributing to the horse’s pain and lameness.” Many horses can show old, non-active injuries or other chronic changes that are not related to that horse’s present condition. 

Nuclear scintigraphy is another dynamic modality that can provide evidence that an SI joint is indeed currently inflamed and irritated. A nuclear-labeled product is injected into the horse. This substance circulates throughout the horse’s body and it is picked up or concentrated only in areas where there has been damage and undergoing repair. A specialized scan of the body is done next, and the nuclear material that has been incorporated into these active areas shows up as “hot that horse’s present condition. 

Nuclear scintigraphy is another dynamic modality that can provide evidence that an SI joint is indeed currently inflamed and irritated. A nuclear-labeled product is injected into the horse. This substance circulates throughout the horse’s body and it is picked up or concentrated only in areas where there has been damage and undergoing repair. A specialized scan of the body is done next, and the nuclear material that has been incorporated into these active areas shows up as “hot spots,” or areas of concentration. This alerts the clinician to those active areas that are directly related to that horse’s present problem. 

Research is also currently underway to develop the capabilities to produce a full-body CAT scan in the standing, sedated horse. This technology would drastically improve the way that SI problems are diagnosed and would allow clinicians to actually image the SI joint, with minimal risk to the horse, and to be able to evaluate its soft-tissue connections as well. Though not currently available, these units have been produced and are actively being tested and refined in clinical settings.

Treating SI Issues

Once a diagnosis of an SI problem has been made, there are a number of treatment options available for your horse. The SI joint can be injected with anti-inflammatory medication just like any other joint. This medication is intended to reduce the inflammation and pain in that area. Injections can be coupled with muscle-relaxing drugs and other systemic anti-inflammatory medications designed to allow the horse to move more easily and more correctly. While most horses are rested from hard work and competition while they recover from SI issues, controlled physiotherapy is still also very important. Horses are exercised on a very specific program designed to promote mobility of the supporting structures of the SI area and to help strengthen the muscles that stabilize the joint. Acupuncture, pulsed wave electromagnetic energy, therapeutic laser and ultrasound are all also used to help reduce tightness and spasm through the SI area during recovery. 

Research suggests that horses with primary SI injuries take longer to heal and often don’t return to full athletic function. However, horses with a strained SI joint caused by other problems can do very well once the sore joint, strained ligament, imbalanced hoof or inappropriate riding stress is resolved. Learning about the SI joint and how it influences the horse’s basic motion and knowing the early signs of problems are the important steps to getting a diagnosis and setting up a pathway back to a healthy SI joint.  

Sidebar: Underlying Conditions Contributing to SI Issues 

Because of its location and purpose, the SI joint will be put under increased stress when the horse attempts to compensate for other issues. A detailed history in cases of horses with suspected SI pain will help identify known risk factors. Additionally, a complete physical examination will help rule out joint inflammation, foot balance issues, back conditions and other possible contributing factors. 

Horses with suspected SI problems should be carefully evaluated for the following:

• Hock arthritis can make horses reluctant to switch gaits and round through their backs and may inhibit forward motion. 
• High suspensory ligament desmitis (inflammation of the ligament fibers near the top of the cannon bone that can be from mild to severe), especially in the hind legs, can produce similar signs as hock arthritis. 
• Overriding dorsal spinous processes, or kissing spines, can make horses back sore, inhibit forward motion and may manifest as behavioral responses ranging from a subtle reluctance to work, all the way to flat out refusal to go forward under saddle and kicking out. 
• Negative palmar foot angle is relatively common in warmbloods. The pedal bone, or PIII, is the bone inside a horse’s hoof. It is generally thought that the bottom surface of this bone should be at two to seven degrees relative to the ground surface. This creates a slightly toe downward angle and provides the horse with optimal balance and push off the feet, especially the hind legs. Horses with flat to negative palmar foot angles have a PIII bone that is elevated at the cranial edge (toe) and lower at the caudal edge (heel). These horses are essentially standing and moving from a “rocked-back” position, which places additional stress on the hind leg (high suspensory ligaments, hamstrings and gluteal muscles) and on the SI joint area. 

About Kenneth L. Marcella, DVM

Kenneth L. Marcella, DVM, is a graduate of the New York State College of Veterinary Medicine at Cornell University. For more than 30 years, he has treated sporthorses of all disciplines and levels, including international competitors. Marcella has served as a veterinary official at many events around the world, including national championships, world championships and Olympic competitions. He is board-certified in thermal imaging and is currently a member of the board of directors of the American Academy of Thermology. With an undergraduate degree in English from Dartmouth College, Marcella has also written articles for numerous publications. 

This article originally appeared in the Summer 2024 issue of Practical Horseman.

A horse’s external oblique is a broad, triangular-shaped muscle located over the lower abdominal area of the horse that connects from behind the fourth rib to the point of the hip. There are two external obliques, one on each side of the horse. Its functions are to bend or flex the trunk laterally and compress the abdomen. But when this muscle is tight, it can have major implications for your horse. Fortunately, a basic Sportsmassage technique can easily relieve tightness.

Signs of Tightness

As a Sportsmassage practitioner, I often point out that the most overlooked factor in diminished performance is simple muscle tightness. To understand how tightness develops, knowing how muscles work is important. Every muscle has two ends, and each end is connected to a different bone by a tendon. One end is the anchor, which stabilizes the muscle to the bone. The other end is the insertion, where the motion occurs. The middle part of the muscle, which lies between the two ends, is called the belly. The belly is the power or action of the entire muscle and creates overall movement. 

Muscles are made up of many thread-like fibers that run parallel to each other. A muscle is loose and functioning properly when the fibers have equal and appropriate spaces between them and do not lie very close or touch one another. When the fibers are close together without much space between them, the muscle is in a shortened state and is tight. 

When the muscle is tight, less blood can circulate through the limited space between the fibers. Since blood carries oxygen, the diminished blood flow affects the level of oxygen available to the muscle tissue. Oxygen provides the fuel and energy to the muscle necessary for the required exercise. As the physical exercise increases, the body’s demand for more oxygen increases. Diminished oxygen creates fatigue and discomfort in the active muscles. It is similar to stepping on a hose. The less space in the hose, the less water can flow through.

When muscles are functioning properly, they contract (shorten) and release (lengthen) in synchrony. Muscle tightness affects the release process of the muscle. When a muscle is tight it resists letting go, or releasing, to accomplish the required motion. The tighter the muscle, then the greater the resistance. And the greater the resistance, the harder it is for the horse to move and perform. 

Firsthand Experiences

Olympic eventer Lauren Nicholson and dressage trainer and rider Rebecca Reed have experienced this issue firsthand. 

For Rebecca, she noticed her 13-year-old Oldenburg gelding Simply Sinatra, currently competing in Prix. St. Georges, was having trouble bending, particularly in the left half-pass. 

For Lauren’s 2022 FEI World Championships team silver medalist partner Vermiculus, a 16-year-old Anglo-Arabian, his tight obliques led to him compensate in other areas to keep his balance. This resulted in atrophy of certain muscles that he wasn’t using correctly. “He’s little and everything is quite close together, so when his obliques were out of whack, everything went out of whack,” explained Lauren. 

Identifying Tightness in Horses

A horse with a tight external oblique will not be straight in his body. If the muscle is tight on one side, then the rider will need to use more leg on the side of the tightness. For example, if a horse has a tight left external oblique, he will shift his haunches to the left and will not be able to release the haunches to the right to straighten his body, requiring the rider to use more left leg to keep him straight. Many riders accept this as natural crookedness. The horse will also not back up straight, and he may fall in or out on a circle depending on the affected side.

If both the right and left external obliques are tight, the horse will be quite resistant and have a harder time going forward in all movements and especially in collected work. Jumping horses may also knock down rails.

Causes of Tightness

There are several reasons for tight external obliques. Some of the most common are:

• repetition of lateral work
• cow kicking at flies
• repeatedly kicking in the stall or trailer

Tight external obliques can also be caused by veterinary issues, such as: 

• hindgut or gastrointestinal issues
• problems with the sacroiliac area
• lower lumbar vertebral issues

Gait Analysis and Assessment 

To assess your horse’s motion, have a handler walk him in a straight line about 50–75 feet directly away from you and then turn around and walk back in a straight line. Make sure to do the assessment on soft but firm footing that is flat and even. The walk is the best gait to assess muscle tightness because the slower the horse moves, the more muscle he has to use, and the easier it will be for you to see any resistance in motion. If the horse has external oblique tightness, you should be able to see that he is not straight and is shifting his haunches in one direction. So if he’s putting his hips to the left, it suggests that his left external oblique is tight. 

Relieve Tightness with Cross-Fiber Friction 

Eliminating tightness in this muscle is very easy by using cross-fiber friction. This helps to mechanically break up a spasm or knot by separating the muscle fibers that are stuck together. The entire muscle then becomes more pliable and functional, helping to increase the range of motion and improve specific performance problems.

To locate the external oblique, feel for the bony landmark of the point of the hip, then drop your thumb down on a diagonal in front of the point of the hip about 1 inch. This is where the tendon fibers and muscle fibers meet, at the insertion. Another way to locate it is to imagine the point of the hip is the face of a clock. The insertion can be felt at 7:00–8:00 on the left side, while it is at 4:00–5:00 on the right side. If this muscle is tight, you should feel a small piece of tissue close to the bone that feels like a thick chord or guitar string. If it is not tight, the tissue will feel soft and rebound into your hand. 

Next, I’ll explain the cross-fiber friction technique, but if at any time when applying the technique, the horse threatens to kick, moves away, pins his ears or obviously doesn’t like it—stop immediately. 

Applying Cross-Fiber Friction

Start the technique by using moderate pressure at the insertion with a thumb or two fingers. Cross the fibers diagonally back and forth on the thick chord as if you were going across the grain of a piece of wood. To do this, move your fingers back and forth across the tissue without taking your fingers off of them. Use the cross-fiber friction technique for no more than 10 seconds. Stop and feel the tissue to determine if the chord has softened or changed. If it feels softened or changed, do not repeat the technique. If it still feels tight, repeat cross-fiber friction one more time for no more than 10 seconds. 

Once the technique has been completed, it is best to ride or longe the horse afterward. Exercise may enhance the treatment because it further lengthens the muscle. If you’ve relieved the tightness, you will see new or improved range of motion. The change is immediate. Canter the horse in a connected long and low frame two times in both directions around an arena—as long as horse and rider are safe to do so. The canter is the most concerted exercise in lengthening all of the horse’s muscle groups. That is why the trot always feels better after the canter. You may choose to trot or longe the horse if cantering is not an option. If you cannot ride the horse following the technique, then ride him when you are able—there is always another day.

Proven Results

Both Rebecca and Lauren saw marked changes in their horses after their external obliques were loosened. After the Sportsmassage technique was used on Simply Sinatra, everything became much easier right away. This allowed his right hind to come underneath and cross over to the left. “The [half-pass] was easier, it flowed much better, the connection was better, everything was better,” said Rebecca. Lauren agreed that the effect was instantaneous, but also had benefits over time. “The other muscle groups aren’t compensating and they can develop properly and they get better long-term, too.”  

If your horse continues to have this problem in motion, seek a veterinarian assessment to help address the cause.  

About Jo-Ann Wilson

Jo-Ann Wilson is a licensed massage therapist, clinician, author, teacher and researcher whose work includes serving horses and riders of all levels and disciplines for over 30 years. She was a longstanding associate and partner of the late Jack Meagher, pioneer of Sportsmassage, and is the director of Wilson Meagher Sports Therapy, which offers clinical and educational programs in the Wilson Meagher Method of Equine Sportsmassage.

She has served as the sports therapist for the U.S. and Canadian Eventing Teams at multiple Olympic, World Equestrian and Pan American Games. Wilson also offers online video training on her website and YouTube channel, as well as live workshops. For more information, go to sportsmassageinc.com.Wilson recently wrote and released her book, “Keeping Horses At Their Best: A Hands-On Guide to Equine Sportsmassage.” Parts of this article were adapted from her book. To purchase a copy, click here.

Practical Horseman thanks Kristina Watkins of Firefly Farm in Reddick, Florida, for use of her farm and horse for the demonstration.

This article originally appeared in the Spring 2024 issue of Practical Horseman.

Trauma to the knee can occur in a number of ways in any type of horse and at any age. Faulty conformation can be a factor, with offset joints (“bench” knees) or outside, forward or backward deviations carrying an increased risk of injury and lameness. However, regardless of build, the more a sporthorse is campaigned, the more likely he is to incur wear and tear or outright injury to this complex, weight-bearing joint. 

Early diagnosis of the nature of the problem, followed by timely, conscientious treatment, offers the best chance of keeping an acute knee injury from turning chronic and possibly ending a sporthorse’s career. 

Diagram of an Equine Knee Injury

First, a very basic anatomy lesson about a joint that is anything but basic:

The horse’s carpus, or knee, consists of a number of small bones that form two rows and connect in three primary sub-structures: the radiocarpal, intercarpal and carpometacarpal joints (see diagram on right). Most of a horse’s weight is carried in the medial aspects (the inner half) of the radiocarpal and intercarpal joints, with movement occurring on the medial side of the knee.

These bones, which join the radius at the top of the knee and the cannon and splint bones below the knee, are held together by a complex series of ligaments. Besides maintaining joint stability, these ligaments act as shock absorbers during motion. The knee problems most common in sporthorses generally fall into one or more of the following categories, keeping in mind that they sometimes overlap. In laymen’s terms, these are:

1. Soft tissue injuries (the ligaments, cartilage, etc.) in and around the joint. This is what generally occurs in twist sprains, strains, pulls, etc., and can include a common condition called proximal suspensory ligament
desmitis. A “big” or “popped” (swollen) knee can be indicative of merely tissue inflammation, or the inflammation could be part of a more complex situation involving the structure beneath it. 

2. Wounds. Gashes, lacerations and the like can be either superficial or extend deeper into the tissue. Like the inflammation that often accompanies them, they can also be just one component of a more complex injury involving the knee’s inner workings. Loss of synovial fluid (the joint’s essential lubricant), the potential for infection of the joint (which can become chronic) and scar tissue buildup can be complicating factors in this type of knee injury. 

3. Bone issues. Trauma and wear to the joint, as well as accompanying inflammation, can result in regenerative changes to the bone (such as
remodeling or increased density—think bone spurs), not to mention chips and fractures. Included in this category are ailments like subchondral bone disease of the third carpal bone and third carpal bone sclerosis (or even both), which are seen a lot in racehorses.

4. Osteoarthritis.  Just like in humans, this degenerative disease develops in joints as a result of trauma or just plain wear and tear; inflammation is both a contributing factor and a result. In equines, one type of osteoarthritis develops as a response to stress-related changes, fractures or chips in the bone and damage to the cartilage (think young racehorses in hard training, for example). A second type, seen more often in older horses, appears to develop without the same cycle of exercise-induced bone and cartilage remodeling and damage. Over time, loss of synovial fluid results in a gradual decrease/breakdown of cartilage thickness and an increase in friction within the joint (bone rubbing against bone). This degeneration, combined with weakening of related ligaments, can produce the “creakiness” and instability often associated with arthritis in a senior equine. Like your grandpa’s “trick knee,” this is often what is occurring in a “chronic” knee problem.

Diagnosis

It’s hardly surprising that acute knee injuries are most common in disciplines involving speed and/or jumping. They are often the immediate result of trauma and will occasionally require surgery.

By contrast, “wear and tear” to the joint can occur over time in virtually any horse sport, simply as a result of repetitive motion; this can present as either a gradual, intermittent or sudden-onset lameness. “One acute overuse soft-tissue injury in the back of carpus is proximal superficial digital tendonitis, aka ‘high bowed tendon,’” noted Elizabeth J. Davidson, DVM, DACVS, DACVSMR, associate professor of Equine Sports Medicine at New Bolton Center in Kennett Square, Pennsylvania. “This injury most commonly occurs in the middle-aged or older sporthorses,” she added.

Regardless of the cause, one thing is clear: Early intervention is critical if treatment and rehabilitation of an acute knee injury are to be successful. 

“In the sporthorses I see, the most common knee injuries are typically from hitting their knees (on something such as a jump), falling on flexed knees or sustaining lacerations,” noted Caitlyn Horne, DVM, ACVSMR Equine Sports Medicine and Rehabilitation at North Carolina State University’s College of Veterinary Medicine. “Getting an early accurate diagnosis of what structures are involved—and to what degree—helps [us] make early, more effective treatment decisions. Treating a knee once the process of osteoarthritis has already started or a significant scar has already formed is going to be more difficult.”

Dr. Davidson stressed the same point, adding, “The knee is a complex anatomical structure. There are many small carpal bones. There are important soft tissue structures along the palmar (back) of the carpus.” This includes the aspect of the suspensory ligament that lies just below and behind the carpus. 

“There are also important synovial structures including the carpal joints, joint capsules and the carpal canal. Acute knee injury can damage any of these anatomical structures depending on the type of injury. Also, the dorsal carpus has extensor tendons and tendon sheaths.”

Unless the injury’s location is painfully obvious, a lameness is generally traced to the knee through a combination of physical examination, gait check, flexion tests and nerve blocks. 

Then the real work begins; because the knee involves so many parts, X-rays and ultrasound are especially useful in pinpointing the exact nature of the problem. “In acute injury, the carpus may be swollen, which can make acute identification of underlying internal damage to the important bone and/or soft tissue structures of the carpus difficult,” Dr. Davidson said. In these cases, advanced imaging like magnetic resonance imaging (MRI) and computerized tomography (CT) scans might be necessary to determine which structures are involved. By contrast, swelling can be subtle or even absent in some knee injuries, Dr. Davidson noted, “ … especially palmar [back] of the carpus injuries. Veterinary evaluation including diagnostics is recommended.”

Wounds and/or lacerations to the knee present yet another set of potential issues. “It is important to assess if the wound communicates with a synovial structure and/or has caused penetrating damage to the bones and/or soft tissues,” Dr. Davidson said. “Without prompt identification, a wound that penetrates a synovial structure can result in an infected joint or tendon sheath,” she added, noting that “chronic sepsis of a synovial structure is very difficult to treat effectively.”

After applying cold therapy to a knee injury to reduce inflammation and swelling, the knee might be bandaged initially to immobilize it and to prevent infection if the injury involved a wound or laceration.

Treatment 

The type and length of treatment that is required to heal a horse’s “bum” knee will naturally depend on the type, location and degree of the injury. Considerations to determine these factors include which tissues are involved, whether the joint or carpal sheaths are implicated, whether there is a wound, cartilage tears or damage to the bone, etc.

If a ligament has been torn, for example, prepare for weeks or even months of rest, hand-walking and a gradual return to exercise as dictated by your veterinarian. As Dr. Davidson noted, “Soft tissue injuries tend to take longer to heal and often required prolonged confinement and controlled exercise program. If the soft tissue injury is missed (not identified), the horse may inadvertently be placed back into exercise too quickly; the missed soft tissue injury may not have healed adequately which may prolong healing and/or result in re-injury. 

“Bone fragmentation and/or small fractures can also be missed without veterinary evaluation, and without adequate and appropriate treatment, any joint injury can result in
arthritis,” she said.

Generally speaking, the first priority after a knee injury will be decreasing any heat and inflammation. This is important to help reduce both the pain now and the risk of chronic degeneration (and even more pain) down the line. 

Conventional anti-inflammatory treatment usually starts with cold therapy, such as icing or poultices, immediately after a traumatic injury. The knee might also be bandaged initially to immobilize it. Then, depending upon the diagnosis, non-steroidal anti-inflammatories such as phenylbutazone (bute) might be given to address the pain, keeping in mind that the risk of gastrointestinal and kidney issues increases with long-term use of NSAIDs. Going forward, your veterinarian might consider regular use of anti-inflammatory medications or even injections of drugs (either non-steroidal or steroidal) to address chronic knee problems.

Corticosteroids can provide powerful, even dramatic relief of inflammation and pain. Some types also offer a degree of joint protection and—if administered with hyaluronic acid—joint lubrication, as well. However, it’s wise to reserve corticosteroids in particular for conservative use when nothing else seems to work. This is because excessive or long-term administration of certain steroids can, ironically, result in cartilage breakdown and even contribute to the onset of laminitis. 

Polysulfated glycosaminoglycan (Adequan^®) or hyaluronate sodium (Legend^®) injections are common non-steroidal options for maintaining joint soundness in older sporthorses. Adequan is said to help increase HA production and decrease synovial inflammation, while Legend is reportedly intended to treat joint dysfunction related to synovitis (inflammation of the synovial membrane) associated with osteoarthritis.

And don’t discount novel regenerative therapies; these are gaining popularity as alternative ways to treat joint issues without steroids. “The regenerative therapy that we use most commonly in the knee is IRAP [Interleukin-I Receptor Antagonist Protein],” said Dr. Horne. “We use this in multiple ways, as an anti-inflammatory after an acute injury, as a post-operative series after surgery or as a maintenance therapy for a chronic knee injury.”

For older horses who have sustained knee injuries, a “whole-body” approach might also be worth exploring because over time, an injury in one leg can lead to overcompensation and soreness elsewhere, too. Possible treatments along these lines include judicious non-steroidal therapy in the form of either phenylbutazone or firocoxib, a COX-2 inhibitor that can often be given to
horses who are sensitive to more conventional NSAIDs. 

Rehab Best Practices

The length of confinement and rehabilitation required by a knee issue—and the timing of a controlled exercise program—will obviously vary with the diagnosis and severity of the problem(s).

Of particular concern during rehabilitation is maintaining the complex range of motion in such a normally flexible joint. “One of the common issues I see in treating and rehabbing acute and chronic knee injuries is that flexion of the knee can be very painful,” Dr. Horne commented. “It is important to address this early, as it can then turn into a chronic problem that is more difficult to treat.

“The knee is normally capable of a large degree of flexion, and it is important after any type of injury to keep this range of motion,” she explained. “In the acute stage, it is important to try to get the horse as comfortable as possible quickly by decreasing the associated swelling and any intra-articular effusion [fluid accumulation within the joint]. Sometimes this can be done with just simple things, such as cryotherapy [icing] and compression bandaging.

“Once the horse is comfortable, initiating early range-of-motion exercises is critical in order to prevent future loss of range of motion and encourage a healthy joint environment,” Dr. Horne continued. Depending on the case and comfort level, she said one could start with just passive range-of-motion exercises (ask your vet to demonstrate) or both passive and active range-of-motion exercises, such as work over ground poles and cavalletti.

Range-of-motion exercises can be tricky, however, where wounds and lacerations are concerned because of the risk of tearing the wound open. Wounds also bring with them the prospect of scar tissue buildup, which can further impede motion over time. “We do see chronic scars from old wounds or extensor tendon injuries [over the knee],” Dr. Horne confirmed.

Because of this, she said it might be necessary in such cases to temporarily limit knee motion to allow the wound to heal more effectively. This is why “… getting early veterinary care can be very important in these cases,” she said, adding, “Once the wound has healed, addressing the scar early is important to prevent decreased range of motion later.”

So, let’s say your horse got lucky—he wrenched his knee but appears to have recovered; the swelling has subsided, and he now seems to be moving sounder than ever. However, if he didn’t have a full veterinary evaluation, don’t be fooled by appearances, Dr. Davidson warned. 

“Many horses become comfortable and/or sound BEFORE the underlying injury(s) has healed, which can give one a ‘false sense’ of security about the actual tissue healing,” she said. “And a too-early return to exercise and/or turn-out can result in re-injury of an inadequately healed injury. Therefore, relying on the horse’s comfort as the only criteria to determine if the horse is ready to go back to work can be inadequate and misleading,” she explained.

To this end, Dr. Davidson recommended periodic re-assessment of both horse comfort and the actual injury by a qualified veterinarian. (Ultrasound scans are one tool that can be helpful here.) “Minor injury might require a few re-assessments. Major injury might require numerous periodic re-assessments throughout the injured tissue’s healing process,” she noted.

Conscientious conditioning and management will go a long way toward maintaining a rehabbed knee and even preventing future knee injuries. Four key takeaways:

1. During your horse’s “down time,” do as much as you can—within comfortable levels—to maintain his knee’s range of motion.
2. Whether bringing your horse back from injury or maintaining his usual schedule, make any changes in the type or intensity of his work gradual. Space out longer sessions and keep a close eye on his responses. 
3. Bear in mind that the fibers in torn or stressed ligaments heal/remodel slowly, and the “repairs” might be weaker, less elastic and more prone to injury than before. 
4. Remember that every case is different, and knees, like all joints, undergo changes over time. Keep your veterinarian apprised of your horse’s progress and seek his or her guidance about how to proceed.

A word here about oral supplements: Formulas with glucosamine and chondroitin sulfate in particular are widely used these days to support equine joint health. Experts generally view oral supplements as less effective than injections at reducing pain, inflammation and discomfort after a joint injury. Where some theorize oral supplements might be most helpful is in the prevention of osteoarthritis in joints that have not yet sustained trauma. 

This last part is important since, as Dr. Horne noted, “Osteoarthritis is probably the most common chronic knee problem that we see.” She went on to say, however, “I do not think chronic joint problems are necessarily inevitable, as there are lot of factors that play into osteoarthritis, such as genetics, the job of the horse and how the horse has been managed. 

“I think we continue to learn a lot about joint health and have learned a lot from human medicine about [the fact that] early rehabilitation intervention is critical to help reestablish a healthy joint environment.” 

This article originally appeared in the Spring 2022 issue of Practical Horseman.

We’ve all heard the saying, “No hoof, no horse.” But a horse’s eyesight is just as important as those four feet. In the wild, poor vision could mean the difference between life and death if a horse couldn’t spot predators in time to avoid danger. Even a modern, domesticated horse can have his performance life drastically altered or cut short if eye trouble leads to blindness or distorted vision. And some eye troubles, such as cancer, can lead to issues affecting the horse’s overall health.

No wonder we get excited when science pushes forward our ability to diagnose and treat disorders of the equine eye. Here, researchers from universities across the country share some of their latest advancements to help our horses maintain healthy eyes and good vision.

Imaging and Diagnostics: Corneal In Vivo Confocal Microscopy

For any type of health problem, a correct diagnosis is essential to treatment, and various forms of imaging play an important role.

Equine eye issues are no different, and one of the newer techniques giving veterinarians better insights is corneal in vivo confocal microscopy, according to Eric C. Ledbetter, DVM, DACVO, an associate professor of ophthalmology and ophthalmology section chief at Cornell University’s Hospital for Animals.

This imaging technique centers around a confocal microscope, which uses a narrow beam of light to take multiple two-dimensional images of the eye at different depths. The images are automatically reconstructed into a three-dimensional view. In use, the confocal microscope is attached to an adjustable table mounted on a mobile desk, says Dr. Ledbetter. It’s run by a computer with a standard monitor for viewing.

The exam is often performed at a veterinary hospital utilizing standing sedation and topical anesthetic.

Using this procedure, veterinarians can evaluate all layers of the horse’s cornea, including deep corneal lesions that are otherwise not accessible for diagnostic evaluation, says Dr. Ledbetter. It’s also useful for diagnosing other corneal issues, including infections, various autoimmune conditions, tumors, foreign bodies and more.

Dr. Ledbetter and his Cornell colleagues were the first to report the use of this imaging technique in horses and are the only group to have published descriptions of its use in horses. (The technique has shown promise in other species, including dogs.)

“This is a noninvasive imaging technique that allows the cornea to be evaluated in real time with magnification and resolution similar to histology of a standard biopsy but without any cutting or other damage to the horse’s tissues,” says Dr. Ledbetter. “I often explain it as a virtual biopsy.”

Also, a small camera can project the images immediately for the veterinarian to interpret. Fortunately, this means the horse owner doesn’t have to wait days to hear back on results from a biopsy.

The equipment required for the technique is expensive—typically costing more than $50,000 for a unit, according to Dr. Ledbetter. The cost to perform an examination varies by facility, but Dr. Ledbetter notes that it is relatively low and can prevent the need for other forms of diagnostic testing. In addition, the procedure can potentially reduce treatment costs while improving outcomes by providing a specific diagnosis early in the course of the disease.

Corneal in vivo confocal microscopy is available only in a limited number of locations worldwide. However, its availability is spreading, says Dr. Ledbetter, who notes the technology has been used at Cornell for several years to evaluate equine eyes.

Treatment Delivery Method: Direct Medication Injection

Giving eye drops is a common method for medicating the equine eye. However, it can be time-consuming for the owner to administer, and over time the horse can become difficult to treat as he tries to avoid the drops. In addition, drops can be an inefficient way to administer medication, particularly to the cornea, says Brian Gilger, DVM, MS, DACVO, DABT, professor of ophthalmology at the North Carolina State University College of Veterinary Medicine.

“The cornea is normally about 1 mm thick,” he explains. “When it becomes diseased, it becomes much thicker. Using standard eye drops, it’s very difficult to get medication down deep enough.” That can mean that the horse faces surgery and the possibility of a corneal transplant.

Now, says Dr. Gilger, a new type of needle makes it very simple to inject medication exactly where it’s needed. “It’s a completely new injection device,” he says. “It precisely injects where you want the drug to go and does not rely on treating the entire ocular surface.”

With the horse standing but tranquilized—and typically at a veterinary clinic—the veterinarian administers a local topical anesthetic, then uses imagery (via high-frequency ultrasound) to guide the injection and deliver medication directly into the affected area of the cornea.

Dr. Gilger adds, “The goal is to provide treatment about every three days instead of every two to four hours with eye drops.”

Dr. Gilger says the procedure can effectively heal fungal keratitis (inflammation of the cornea caused by fungal infection) and other diseases where the entire eye doesn’t need to be treated. As a bonus, the treatment can cost just $200 to $300 versus, for example, standard fungal keratitis treatments, which can run $1,000 to $2,000.

“This type of treatment will probably completely replace eye drops in the next few years,” Dr. Gilger predicts.

Treatment Procedure: Corneal Cross-Linking

The horse’s cornea is a common place for injuries or ulcers, which may stem from various causes, including trauma, fungus or bacteria. Corneal issues can cause serious problems, including scarring and loss of sight. In some cases, corneal ulcers open the door to bacterial or fungal infection. This can accelerate the ulceration and lead to a jelly-like or liquefied appearance of the eye, often referred to as “corneal melting.” If medical treatment isn’t effective for corneal issues, the horse may require surgery, which could include inserting a catheter to provide continuous medication to the eye.

A new technique called corneal cross-linking has the potential to fix the problem through a nonsurgical, in-patient procedure, according to Dr. Gilger.

With corneal cross-linking, the veterinarian applies riboflavin (vitamin B) eye drops to the surface of the cornea. (Dr. Gilger notes that improved techniques for application are being developed, such as local injection.) The veterinarian then shines a UV light onto the eye, which activates the riboflavin, creating bonds between the collagen fibers in the eye. This stabilizes and strengthens the cornea to prevent melting and also kills the infection, says Dr. Gilger.

The procedure itself can cost around $500 and is widely used in Europe and beginning to see more use in the U.S. One drawback, says Dr. Gilger, is that it is currently a lengthy procedure. It takes 30 minutes or more to administer the eye drops and another 30 minutes for the UV light application, he explains. Additional research is now focused on testing different techniques to speed up the process.

Treatment Procedure: Stem-Cell Therapy

Immune-mediated keratitis is a common equine eye condition, says Dr. Gilger. With IMMK, the horse’s own immune system essentially attacks cells in the cornea. It can lead to inflammation, cloudiness of the eye and blood vessels growing into the cornea. It is considered a chronic disease that can wax and wane for years and ultimately lead to blindness, says Dr. Gilger.

Treatment typically involves daily application of steroids. However, the medication can have long-term side effects. “Topical use of steroids puts the horse at risk for developing corneal infections, such as fungal keratitis, and can result in corneal degeneration when used for a long period of time,” says Dr. Gilger. “Furthermore, if the eye is injured when topical steroids are being used, then the eye heals much slower than normal.” Yet if treatment is stopped, the problem can come back.

Dr. Gilger has been working on a stem-cell-based solution with his NCSU colleague Lauren Schnabel, DVM, PhD, DACVS, DACVSMR, an assistant professor of equine orthopedic surgery and stem-cell researcher, along with ophthalmology resident Amanda Davis.

“We can now safely harvest stem cells from [the IMMK patient’s] bone marrow, grow [more cells] in the lab, inject them back into the horse’s eye and stop the immune response plus aid with healing,” says Dr. Schnabel.

Harvesting the cells costs about $1,800 and involves using a needle inserted into a bone (often the horse’s sternum) to remove stem cells. During the procedure, the horse is sedated, and a local anesthetic is used to numb the site. Stem cells not used for the initial treatment are frozen for future use, and any repeat injections run about $500, says Dr. Gilger.

While the treatment takes a couple of weeks to develop—time for the stem cells to grow in the lab—since IMMK is a chronic condition, waiting a little longer for a treatment won’t make much difference to the horse, says Dr. Schnabel.

During research on the procedure, the stem-cell therapy cleared the disease in a few patients—some of whom needed no additional treatment. Other horses showed a lesser response but still improved. This difference is an inherent challenge when stem cells are taken from the patient, says Dr. Schnabel.

“There is variation in the quality of stem cells from patient to patient,” she explains. “What you get from a 3-year-old horse is different [than] what you get from a 20-year-old horse or a horse that might have other issues.”

That’s why future research may include using cells from a horse other than the patient—a horse with more optimal stem cells—to remove some of that variability in results. Researchers will also be working to determine the best delivery method for the treatment—one that will ensure the best distribution and work most effectively over the long term, says Dr. Schnabel.

More to Come

These are just a few of the promising advancements in equine eye care now available to veterinarians. More research is constantly in the works. There’s little doubt that owners can expect more innovation soon to help keep their horses’ eyes healthy and vision crystal clear. 

7 Insights into Equine Vision

1. From light to images. As light enters the horse’s eye, it passes through the cornea, aqueous humor, lens and vitreous humor. These structures refract, or bend, the light and focus it onto the retina. At this point, the light is converted to an electrical signal that travels out of the eye, along the optic nerve, to the brain. The brain interprets it as images, or vision.

2. Binocular and monocular vision. The horse’s eyes are placed on the side of his skull, giving him a wide arc of monocular vision on each side and a roughly 65-degree arc of binocular vision in front. With monocular vision, the horse sees different things through each eye, although the brain shares the information from each side. (This lays to rest the myth that what a horse sees with one eye isn’t recognized through the other eye.) Binocular vision allows the horse to see the same thing with both eyes at once. With this wide range of vision from monocular and binocular viewing, horses can see more of the world around them at any given moment than a human. When your horse spooks or startles, it may be caused by something you can’t see without turning your head.

3. Blind spots. This eye placement also gives the horse blind spots—notably behind himself and for a space of about 4 feet in front of him. To adjust for this front vision limitation, a horse will naturally raise, lower or tilt his head to see better—which could explain why so many horses reflexively move their head upward as you raise a hand to their forehead. It’s also worth noting that a horse ridden with his nose on or behind the vertical cannot see directly in front of himself.

4. Night vision. Horses do have fairly good vision in low-light conditions. That’s because their large eyes, combined with their horizontal pupils, help them capture more light.

5. Color vision. Horses can see some colors, although they probably don’t see them as vibrantly as people do. In general, they can see the green–yellow spectrum and the blue–gray spectrum. They can’t see red.

6. Eye care. To help keep your horse’s eyes in good health, reduce the chance of irritation from dust, insects and UV light. A fly mask may help as well as providing shade during peak sunlight hours. Also work to decrease the risk of trauma by paying attention to stabling and pasture. Low tree branches, thorny plants, hooks or other sharp objects can be hazardous.

7. Signs of trouble. If you notice that your horse is squinting, rubbing an eye or suddenly acting head shy, these could be signs of eye trouble. Also watch for tearing, squinting, redness, cloudiness or lumps and bumps around the eye. If you suspect a problem, don’t hesitate to call your veterinarian since treatment delays could increase the risk of a serious issue.

This article was originally published in the September 2018 issue of Practical Horseman. 

If you think passage is a challenging movement, you’re right. And science just proved it.

On the surface, passage is simply a very slow, very animated trot. Look deeper, though, and a host of biomechanical variables come into play. Identifying those variables was the goal of a recent study led by Hilary Clayton, BVMS, PhD, Dipl. ACVSMR, MRCVS, Mary Anne McPhail Dressage Chair Emerita at Michigan State University and president of Sport Horse Science, LC, and Sarah Jane Hobbs, lead for the research and consultancy in equine surfaces team at the University of Central Lancashire in England.

The passage study was part of a multi-year research project aimed at understanding the mechanics of collection and self-carriage, says Dr. Clayton. It involved the use of a 10-camera motion-analysis system to film three highly trained Lusitano dressage horses performing passage over a set of four force-measurement plates. The plates allowed the researchers to measure the three-dimensional forces of the horses’ footfalls. Body markers helped researchers track each horse’s center of mass and measure balance variables, including pitching moments, limb position relative to the center of mass, trunk posture and the timing of footfalls.

Pitching moments are when the horse’s body rotates around its center of gravity—nose up as the hind limbs swing forward and nose down as the weight shifts onto the forelimbs, explains Dr. Clayton. The researchers found that in passage the horses’ pitching rotation was reduced and they maintained an overall more uphill carriage.

To accomplish this, the horses had to make multiple simultaneous adjustments to their limb positioning and their production of muscle force. Notably, says Dr. Clayton, horses placed their hind hooves a little farther forward under the body and adjusted forces independently in the forelimbs and hind limbs. Researchers also found that while riders tend to associate the hind end with collection, the forelimbs actually played a crucial role in maintaining uphill balance.

“In summary, because the forward velocity of passage is slow, it challenges the horse’s balance,” says Dr. Clayton. “Horses must learn how to adjust the timing of their footfalls, the hoof-placement position and, very importantly, the way that the fore- and hind limbs push against the ground in order to perform a correct passage in good balance. As you can imagine, it’s difficult to teach a horse to do all these things, and some horses never learn the correct technique.”

Spoiler alert: Dr. Clayton notes that yet-unpublished data shows “piaffe is an entirely different beast from passage.” Stay tuned! 

This article was originally published in the February 2018 issue of Practical Horseman.