Osteochondrosis dessicans (OCD) of the tarsocrural joint is common in many breeds of horses, especially Warmbloods and Standardbreds. OCD of the tarsocrural joint may or may not be associated with lameness and is associated with variable amounts of joint effusion. Diagnosis is confirmed by intra-articular analgesia of the tarsocrural joint if lameness is present and by demonstrating radiologic changes. Few of the common OCD lesions in the hock will heal spontaneously after 5 mo of age, so arthroscopic surgical removal is usually advised. Prognosis for full return to athletic function after surgery is good. If left untreated, fragments may come loose, resulting in cartilage damage and acute signs of effusion and lameness.
OCD lesions in the tarsocrural joint are most commonly seen on the distal intermediate ridge of the tibia. Lesions at this site do not cause lameness unless significant effusion occurs or fragments become loose. Dislodged fragments may become lodged in the dorsal part of the proximal intertarsal joint. Arthroscopic removal of the fragments is usually associated with a good outcome.
OCD lesions of the distal end of the lateral trochlear ridge are most commonly seen in heavy horses and Standardbreds. Lesions can be large and, if loose, cause acute onset of severe lameness and effusion. Large or loose lesions should be removed arthroscopically, and even large lesions can be removed with a good prognosis. Prognosis is determined by the proximal and axial extent of the lesion.
Medial malleolar OCD lesions usually cause more lameness and effusion than the more common OCD lesions on the distal intermediate ridge of the tibia. They are usually seen on the axial aspect of the medial malleolus and may be overlooked on dorsoplantar radiographs. Early arthroscopic removal of fragments is recommended to prevent erosive lesions from developing on the medial trochlea of the talus. Arthroscopic surgery usually has a good prognosis for return to athletic function.
Lateral malleolar fragments are usually traumatic and are only rarely (1%) OCD lesions.