By: Dr. Lydia Gray
The patella is the small, bony plate (the kneecap) that protects the knee joint in people, where the femur and tibia meet. In horses, this joint is known as the stifle. A unique hooking of the patellar ligaments over a notch on the femur allows the horse to lock its hind legs in the standing position. Unfortunately, if one of these ligaments remains in the hooked position, the horse is unable to bend its hind legs. This condition is known as Upward fixation of the patella and can range from a slight delay in a leg's forward motion to completely locking that freezes a leg for long periods of time. A veterinarian should examine the horse to confirm the diagnosis and rule out other causes of hind leg gait abnormalities such as shivers, stringhalt and fibrotic myopathy.
While the causes are not well understood, there are some factors that horses with this condition share, such as poor muscle conditioning, excessively straight hind leg conformation, stifle trauma, and debilitation. Therefore preventing future episodes may include a conditioning program to strengthen and tone the surrounding muscles and a nutritional program to improve the overall health of the horse. Corrective shoeing may also help.
Horses that don't improve with the conservative approach above may require injections or surgery to prevent Upward fixation of the patella. However, not only are these treatments more aggressive in nature, they do not always correct the condition, so they should only be used as a last resort.
About Dr. Lydia Gray