Onset

IT IS NOT CLEAR what triggers the onset of DSLD. All too often, actual onset is not recognized. Says one prominent researcher, "Most cases go months to years in the early stages before they are diagnosed." Changes are simply too gradual for many owners to notice. It's like gaining the inevitable pound a year, only noticing when your pants don't fit.

Some clues to onset include:

Breed: Many breeds have been diagnosed, among them several gaited breeds, including American Saddlebreds, Peruvian Pasos, Peruvian crosses, Standardbreds and National Show Horses. Some have a higher incidence of reported cases than the general population - among these Arabs, Thoroughbreds and Peruvian Pasos.

Age: Age may or may not be a factor, and varies with breed. "In general, most breeds develop the condition in horses over 15 years of age, or in horses that have been worked inordinately hard over their lives. But in Peruvians, the average age of onset is between five and ten years," explains a leading researcher. "Unfortunately, the average time to diagnosis is from eight to 15 years, meaning the horses have had the condition for some time before they are actually diagnosed." Horses have been diagnosed with early symptoms at one, two, and 26 years of age.

Hormones: Often, mares with no previous history of lameness develop symptoms shortly before or after foaling.

...the hallmark of DSLD is not damage to the suspensories, but how they repair.

Conformation: The newest research numbers challenge the belief that certain conformational faults may predispose a horse to DSLD. Coon?footed horses, those whose pasterns near horizontal while standing, are common among horses that go on to develop DSLD, and most DSLD cases go on to develop a coon-footed stance regardless of their original conformation. But uncounted numbers of congenitally coon-footed horses never develop DSLD. They may have suspensory problems, but maintain the ability to heal correctly.

Similarly, post?legged horses, in which the hind limbs straighten at the stifle and hock, were also suspected to be predisposed to DSLD. Horses diagnosed with DSLD generally become post-legged as the disease progresses, yet countless horses with this fault never develop DSLD.

Since, as the fetlocks drop, the length from hip to fetlock extends, coon-footed horses very often also become post-legged, which is why the two are so commonly seen together. And while not always indicative of DSLD, they are serious flaws that contribute undue stress to the legs.

Progression

"COMMON EARLY SIGNS include stiffness in gait, change in attitude, reluctance to work. Signs that look like back soreness, lack of drive to gait (either in front end extension or rear drive)," cites a noted authority. "Generally no signs in the limbs are seen at this point yet ? i.e. swelling, fluid, painful suspensories, nor is lameness usually noted as of yet. If horses are affected in the rear, often a widening of the rear limbs is noted. Some breeds, like the Peruvian, move very closely in the rear, and with DSLD the hind limbs spread apart during movement."

Other early gait changes may include a rough gait, excessive "looseness" in which the hoof nearly flops, switching from lateral to diagonal movement, short stride, stumbling, or moving more stiffly than usual. Some rush through gait and break to a trot or pace. In some the pasterns drop below horizontal in motion.

Subtle behavioral changes may be early indicators. Some horses resist having their legs touched or feet picked up. Many resist having their legs extended to the front or rear for trimming. Some just seem "off" or "cranky".

...unlike injury or any other known disease, DSLD occurs bilaterally.

One key component to diagnosis is that unlike injury or other diseases, DSLD occurs bilaterally (both fronts or both hinds) or quadrilaterally (all four legs). "It often starts in one limb only and appears to be one-legged (often causing a misdiagnosis at that point), but given time, always spreads," says one of the top vets in the field.

"Over 90% of the time the disease starts in the suspensory ligament branches. This is a common reason it is misdiagnosed or not looked for, because nobody looks there, they look in the body of the suspensory only," this expert continues. The main body becomes involved as the disease progresses.

Lameness may or may not be evident, presenting a tough call, especially for those unfamiliar with the normal movements of gaited horses. "As the condition progresses lameness may become apparent. But because of the bilateral nature of the disease, lameness is not a reliable, consistent sign. Shortening of the stride or a stiffness of gait are often the only signs noted," concurs a leading researcher.

As the suspensories change, they often become puffy looking, but feel hard and "rope-y" to the touch. The area may be hot, swollen and painful. "Again looking for tendon/joint swelling is not consistent, but pain of the suspensory branches almost always occurs as the disease continues," explains one authority.

Late in the process, the fetlocks tend to drop below horizontal, resulting in the "coon-footed" posture, and in cases involving the hind legs, the legs straighten from the croup, through the stifle and hocks, as the fetlocks lower, resulting in a drastic conformational change to "post-legged". (Although, this is not common in cases involving all four legs.)

Despite these "classic signs" a top vet warns, "Some of the worst affected horses I have seen, (involving) all four limbs and in agonizing pain, did not swell anywhere, did not sink in the fetlocks and had almost no conformational changes at all!"

Afflicted horse may give odd clues. Trying to escape the pain, many try to walk on their toes, not bearing weight on their heels. They may stand with one foot drawn up beneath them, pointed at the toe, then shift sides. Many dig holes so that their hind feet can rest in a tilted position. Some literally try to sit in feeders or on fences to take weight off their hooves. They may stay off their feet as much as possible, laying down and even groaning from the pain. It's easy to see why colic is often the first call.

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