Summary
Synovial osteochondromatosis represents a very unusual synovial response in the horse and can be either primary or secondary. The condition describes metaplastic and focal formation of cartilage within the intimal layer of the synovial membrane. The condition is also uncommon in other domestic animals, although occurs more frequently in man. Treatment usually involves arthroscopic removal of osteochondral bodies and resection of abnormal synovium. Recurrence is quite common and malignant transformation rarely occurs although, to date, this has not been reported in the horse.