Description

The stifle joint includes the kneecap and its ligaments and is the most complex joint in the horse. The stifle is similar to the human knee and is found on the hind limbs of the horse.

A thin capsule surrounds the entire stifle joint that has a specialized fluid to help with shock absorption and lubrication. Structural stability is also provided through ligaments in this joint. The inside and outside of the stifle has specific ligaments that keep the leg from bending excessively in either direction.

When the stifle apparatus is working properly the horse is inherently stable, but trauma, rapid changes in direction, and rapid deceleration create pressure that may lead to injury. 

Because of the size and relatively open structure of the stifle, swelling often develops in the joint. When the swelling is accompanied by lameness it is known as gonitis which is a descriptive term rather than a specific diagnosis. Severe stifle injuries are frequently complicated by fractures.

Symptoms

• Swelling
• Thickening of distention of the joint
• Lameness
• Exercise intolerance
• Locked kneecap

Causes

Stifle injuries may be caused by direct trauma to the joint or by stress to the joint area from performance activities that include quick changes in direction, rapid deceleration, and repeated jumps. Such trauma may occur during roping, cutting, reining, barrel racing, and, of course, jumping.

Prevention

Prevention of stifle injuries is dependent on keeping the horse from suffering direct trauma to the stifle joint and by not pushing a horse beyond its capabilities, especially in performance activities. Since the stifle joint is complex and difficult to evaluate radiographically because of its mass, surrounding tissue, and soft tissue structures, owners and handlers need to be watchful for possible stifle injuries and act promptly when injuries are suspected.

Treatment

Treatment follows a definitive diagnosis usually obtained by a veterinarian using a number of tools to evaluate the stifle joint. Digital x-rays, ultrasound, and curvilinear ultrasound probes can be used to obtain images of the collateral ligaments, meniscal surfaces, and other components. Once diagnosed, stifle injuries are treated in much the same way as tendon or ligament injuries in other areas of the horse.

A period of rest to resolve the swelling will allow the joint to begin healing. If the joint capsule is stretched, but not ruptured, recovery is possible given two to three months of rest with a gradual return to activity. In the case of collateral ligament and cruciate ligaments, treatment is often unsuccessful, and the joint becomes unstable and subject to arthritis accompanied by chronic lameness.