Equine tendons and ligaments
Suspensory degeneration is an inherited condition that involves excessive accumulation of proteoglycans in the ligament, weakening it. It has been reported in many breeds; it is most commonly associated with Peruvian Paso horses. Generally this is an aging change in predisposed horses but has been seen with steroid administration and hyperadrenocoriticism, as well.
Degeneration of the suspensory ligament leads to dropped fetlocks and changes in the forces on other structures. The flexor tendons have to assume more concussive force and can become injured secondarily. The other joints become hyperextended as the fetlock drops. The abnormal conformation leads to osteoarthritis in multiple joints.
Ultrasound is typically abnormal due to fiber tearing with the increased stretch.
Treatment is supportive and primarily targeted to the effects on other structures (NSAIDs and support shoeing). Some suggest that using polysulfated glycosaminoglycan (Adequan) for osteoarthritis is contraindicated because it may exacerabate the proteoglycan accumulation in the ligaments. Mild to moderate exercise every other day may be beneficial.
The suspensory ligament can just start to degenerate (no trauma required). This results in bilateral sinking of the fetlocks and a very painful horse. Prognosis is crappy. Don’t give steroids to these horses.
Degenerative suspensory ligament disease in horses. The Horse, 2018