Degenerative suspensory ligament desmitis is a progressive, degenerative condition found in several breeds. It was first discovered in Peruvian Horses, and early-onset DSLD was recognized in some family lines in the 1970s. Many people still think of this as a gaited-horse problem. In recent years, however, DSLD has been diagnosed in many breeds, including Thoroughbreds, Arabians, Quarter Horses and Warmbloods.
“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.

A lateral view of the inner structures of a horse’s lower leg. Courtesy Illustrated Atlas of Clinical Equine Anatomy and Common Disorders of the Horse
“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.”

A palmar, or back, view of the suspensory ligament. Courtesy Illustrated Atlas of Clinical Equine Anatomy and Common Disorders of the Horse
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.
For More:
To read more about suspensory ligament injuries in the dressage horse, click here.
This article was originally published in the Fall 2024 Issue of Practical Horseman Magazine.