Last Updated on February 21, 2022 by Allison Price
Anatomically, the stifle joint of a horse’s hindleg corresponds to the knee joint in a human leg. The horse’s stifle is not visible halfway down the leg like the human knee. It is hidden in the horse’s upper hindleg structure. The patella is a small bone found at the horse’s flank where it connects to the hind leg. The patella is located just above the joint between the horse’s hip and the patella (the upper leg bone that connects into the hip).
When the horse is still, the medial patellar ligament hooks over the notch at the end of his femur. This allows the horse to stand or snooze and can support the stifle.
The ligament will usually slide out of the notch as the horse moves forward with its hind leg. The ligament must not become tangled and cannot be moved forward. If it does, the hind leg will have to be pulled forward by the horse. This condition is also known as a sticking or locking stifle. Although veterinarians refer to the condition as “upward fixation” of the patella, old-time horsemen use a simpler description: “That horse has been stifled.” This trick is often effective.
Although locking stifles don’t affect all breeds of horses or ponies, they are more common in horses with a very straight hindlimb . The horse’s owner cannot correct the problem, but gradual conditioning will strengthen the muscles and reduce the likelihood of locking. Some young horses gained 55 to 100 pounds (25 to 45 kilograms) and had their sticking stifles eased. This may be due to a bigger fat pad behind their patella. Horses that desire to gain weight should not be given more grain, but a gradual increase in their caloric intake.
Corrective shoeing is a way to remove stuck stifles from horses. A farrier can encourage hoof rotation by trimming or applying a lateral wedge to the heel. A rounding of the shoe’s medial edge or hoof can improve medial breakover.
One 1 study that examined treatments for locking stiffles found that 40% of horses had complete recovery and 20% showed marked improvement after corrective shoeing. Corrective trimming combined with exercise and weight gain led to 10% more improvement in the affected horses.
If none of these methods work, a veterinarian can perform one of several procedures that causes mild scarring to the ligament and decreases its elasticity. The ligament becomes less flexible and can be pulled into place more easily than it is able to stretch or stay in place. While these procedures can be used to solve the problem for some horses, they are not as successful for others.
Sticky stifles do not necessarily mean a problem. Horses with mild conditions can still be used as long as the rider remembers that horses should not be expected to move in smooth, athletic manners after being halted. Although these horses might not show classic locking all the time, they may display subtle signs like a shorter stride, difficulty picking-up or maintaining a canter lead, and a little scrambling when climbing or descending hills. Horses with classic locking stifles or horses that don’t have a normal gait after several strides might not be safe to ride.
You can detect a problem with a horse that is being purchased by riding it in all gaits, in circles, as well as in straight lines. You should inspect the horse for any problems when going up or down hills. A skilled horseman/woman will also be able to check for irregular gaits and shorter strides in the hind leg. Avoid horses with obvious conformation problems like crooked legs or straight legs. Ask the veterinarian about any concerns you have during the prepurchase examination.