Osteochondrosis is a common cause of stifle lameness in young horses. Lesions in the stifle most commonly occur on the lateral trochlear ridge of the femur but may also occur on the medial trochlear ridge, in the intertrochlear groove, or on the patella. Lesions are often bilateral and probably develop in the first 6 mo of life. In severe cases, joint effusion and lameness may be evident in foals or yearlings. In less severe cases, clinical signs may not become evident until the horse starts athletic work. In mild cases, clinical signs may be absent. The severity of lameness varies from absent to severe and is often acute in onset. Effusion of the femoropatellar joint is common. Diagnosis may be confirmed by demonstration of radiographic or ultrasonographic changes or by arthroscopy.
Mild lesions in foals have been shown to heal with conservative treatment. More severe lesions in foals may require arthroscopic debridement, but care should be taken not to remove too much of the subchondral bone. In horses with larger defects or fragmentation, arthroscopic surgery is the treatment of choice to remove osteochondral fragments and poorly attached or loose cartilage and to debride abnormal subchondral bone.
In adult horses, the prognosis after surgery for return to athletic soundness is fair to good but depends on the severity of the lesions and the size of the defect in the subchondral bone.