Osteochondritis dissecans (OeD) is a manifestation of osteochondrosis characterized by a focal thickening of joint cartilage and subsequent dissection of a flap of this thickened cartilage away from the underlying subchondral bone. The etiology of this condition remains somewhat of a mystery; trauma, nutrition, ischemia, and hereditary abnormalities of ossification have all been suggested. The disease is usually seen in the faster growing members of large and giant breed dogs. The first clinical signs of lameness are usually noted when the dog is between 5 and 9 months of age. OCD is most commonly recognized in the proximal humerus, but is also found in the distal humerus, distal femur, and tibial tarsal bone. One case of OeD of the distal radius has been reported. Other manifestations of osteochondrosis include ununited anconeal process, fragmented coronoid process, and retained cartilage of metaphyseal growth plates. Current research suggests there may be some relationship between osteochondrosis and the development of cervical spondylolisthesis, slipped femoral capital epiphysis, and hip dysplasia.