Osteochondrosis, also referred to as dyschondroplasia, is a generalized disease of growth cartilage. It affects most common domestic species. It often occurs in rapidly growing pigs approaching market weight or breeding age. Despite much research, the basic cause(s) is unknown but is usually related to the presence of one or more risk factors (below). The disease is characterized clinically by abnormal gait or lameness with characteristic pathologic lesions in cartilage and bone. Lesions of articular surfaces of joints include corrugations and ulcerations of cartilage, separation of cartilage from underlying bone, and development of cartilaginous cysts. Physeal cartilaginous lesions include fractures between the diaphysis and epiphysis or islands of cartilage within epiphyseal or diaphyseal bone. Lesions are often bilateral and symmetrical. Common sites of lesions in joint cartilage include the medial femoral condyle, humeral condyle, humeral head, glenoid of the scapula, distal ulna, and lumbar vertebrae. Common sites of physeal lesions include distal ulna and femur, head of the femur or humerus, and ischial tuberosity.
Dyschondroplasia has been attributed to rapid growth and early, excessive weight-bearing pressure on cartilage. Genetic background is believed to play some role. Other possible risk factors include nutritional deficiencies, flooring and housing that induce trauma, infection with Mycoplasma hyosynoviae, and lack of exercise. The number of pigs with lesions is often much higher than the incidence of lameness would suggest. Although some pigs recover, most affected sows are culled because of the time required for healing and the overall poor response to therapy.