Osteoarthritis (OA), also known as Degenerative Joint Disease (DJD), is the most common joint disease that affects horses, humans, and dogs. OA is a chronic, degenerative process characterized by progressive cartilage deterioration, loss of joint space, marginal osteophyte formation, subchondral bone remodeling, and inflammation of the joint tissues. These processes eventually lead to the breakdown of cartilage in the horse's synovial joint. The most common synovial joints affected in horses include the hock (where it is often referred to as bone spavin), the pastern (where it is called ringbone), the fetlock (called osselets), stifle and knee--and less commonly the neck and back.

Clinical Presentation

Once the joint cartilage begins to degrade, the bones rub together and can cause continued damage and pain. Signs may come and go, stay the same, or result in progressive deterioration of the articular cartilage. Clinical signs of OA most commonly include:

• Lameness
• Pain on flexion or palpation
• Stiffness, which often improves with exercise

OA can occur in all types of performance and pleasure horses, of any age or breed. The disease begins many years before structural joint changes become detectable.

Probable Cause

Most horses develop OA from repeated strenuous exercise inducing mechanical strain or trauma to the joint, rather than a single traumatic event. Factors that contribute to faster onset of OA are training, conformation of the horse, shoeing, breed, use of horse, osteochondrosis lesions (osteochondritis dissecans, subchondral bone cysts), articular fractures, and history of trauma.

Treatment

The main goal for treatment of OA is to reduce pain and prevent further deterioration of the joint by controlling inflammation. Treatment is most effective if it is started during the early stages of OA.