The osteochondrosis is common in sport and racing, horses, it affects the cartilage and subchondral bone. It is characterized by the appearance of cartilaginous fragments osteo more or less free in joints or by slight deformations of the bone. The clinical signs are joint distension possibly with the presence of a lameness. The diagnosis is radiographic. It seems that the breeding conditions, a balanced diet and genetics have a real influence in the development of osteochondrosis.