The suspensory ligament (SL) ties into the top of the cannon bone, just below and behind the carpus in the front limb and the hock in the hind limb. The structure runs down the back of the cannon bone, between the two splint bones. Two-thirds of the way down the cannon, it splits into inside and outside branches which attach to the sesamoid bones at the fetlock. Fibers pass on as the extensor branches blend into the extensor tendons. The SL is a critical structure for the sling function of the fetlock joint and is unfortunately a common site for the development of lameness conditions.
DSLD is a chronic and debilitating syndrome that results in the progressive breakdown of the SL. Recently, DSLD has been found to be a body-wide systemic problem associated with the connective tissue, similar to Marfan’s Syndrome in people. The Peruvian Paso breed is plagued by this problem, although many other breeds are also affected, including the Arabian, American Saddlebred, American Quarter Horse, and Paso Fino breeds.
It is a common finding in older horses, especially aged brood mares that have had many foals.
Common manifestations of this problem include poor performance, lameness, short, choppy gait, and swelling and sinking of the fetlocks, especially in the hind limbs. Usually, more than one limb is involved. DSLD tends to be more common in the hind limbs.
Currently, there is no specific treatment for this syndrome, although regenerative medicine may play a role in future treatments. Definitive diagnosis requires clinical exam with flexion exams and ultrasound. Dr. Kellon’s website describes an herbal approach to treatment (www.drkellon.com).
I personally have seen several cases of mysterious sudden breakdown of the SL in otherwise healthy, young, non-Peruvian Paso Breeds. I never really understood what happened in these cases and there is little that I have learned about the sudden onset of this severe syndrome.
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Prognosis & Relevant Factors
Prognosis is generally poor. The classic form of DSLD in Peruvian Paso horses and older horses of any breed is progressively debilitating with a poor prognosis.
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