Horse Health: Degenerative Suspensory Ligament Desmitis

DSLD is a debilitating syndrome, causing bi-lateral or quadrilateral lameness in horses with no credible history of trauma or injury.

First thought to affect only the Peruvian Paso breed, DSLD is now recognized as a problem in many breeds of horses. It is characterized by dropped fetlocks, horizontal pasterns, straight hocks and stifles and bilateral or quadrilateral limb lameness: Can affect front limbs, hind legs, or both. Frequently the joints become hot and swollen.

Once believed to be a problem with the suspensory ligament alone, it is now apparent that it is more than a breakdown of connective tissue. Some researchers believe that it involves too much accumulation of proteoglycans (a type of protein) between the connective tissues.

More recent findings indicate that it may be a problem with the repair of the normal wear and tear of the ligament. In normal horses “micro-traumas” occur in the ligament during normal exercise. The normal healing process lays down collagen to repair the small lesions. In the horse with DSLD, the repair is accomplished with cartilage instead. Since cartilage is much less flexible, it does not allow the ligament to stretch and extend normally, so pain and breakdown occur.

The bad news is that, at this time, there is no cure for the disease. It is progressive in nature, and ultimately leads to considerable pain and frequently ends with euthanasia. While it is heartbreaking, it can be managed for a period of time with changes in environment and only restricted, natural exercise. A balanced, natural hoof trim with a square toe for easier breakover seems to help most horses with DSLD. There are currently no drugs or therapies that can alter the base process, although MSM (methyl sulfonyl methane) supplementation may be helpful to horses with DSLD, as it is reported to help restore flexibility to tissues. Pain medications are effective in most cases until its most advanced stages.

More bad news is that there is an apparent pre-disposition for the disease. (This could turn out to be good news, in that careful breeding may eliminate the problem in any chosen set of horses.) Although a genetic marker has not yet been found, there is a new diagnosis technique based on biopsy of the nuchal ligament, a big, tough ligament that connects the poll to the withers, and helps hold the horse’s head an neck in position. Test or no test, it would be a poor idea, indeed, to breed an affected horse and risk passing DSLD to the offspring. For that reason, we all wait for a definitive, early test that can diagnose before a horse is bred.

Please note that this advice is neither veterinary nor prescriptive in nature but offered only as an introduction to this topic.

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