Understanding Upward Fixation of the Patella in Horses (Locked Stifles)
By: Dr. Lydia Gray | Updated August 28, 2025 by SmartPak Equine
What Does Upward Fixation of the Patella Mean?
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, or more commonly called locked stifles, and can range from a slight delay in a leg's forward motion to complete 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.
Can I Prevent Episodes of Locked Stifles in My Horse?
While the causes of locking stifle joints 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
- debilitation
Therefore, preventing future episodes of upward fixation of the patella may include a conditioning program to strengthen and tone the surrounding muscles. Additionally, a nutritional program to improve the overall health of the horse may be beneficial. Corrective horse shoeing may also support the horse.
Video on Why Upward Fixation of the Patella Happens in Horses
In this Ask the Vet video on locked stifles, Dr. Gray explains the anatomy of a horse's leg and how this condition may occur, what treatment options are available, and whether this is a lifelong issue.