Transection of the anterior cruciate ligament in the dog: a model of osteoarthritis.

Study of the early stages of osteoarthritis (OA) in humans presents numerous difficulties, since the patient commonly does not seek medical attention until pathologic changes are far advanced and articular cartilage has already been extensively lost. Investigators have, therefore, used animal models to obtain information about the early changes in articular cartilage, bone, and synovium. Among the most widely studied of these models is the cruciate-deficient dog. This report validates the cruciate-deficient dog as a model of progressive OA and emphasizes that, before full-thickness loss of articular cartilage, OA is marked by a phase of cartilage hypertrophy associated with a striking increase in synthesis of matrix macromolecules by the chondrocyte (compensatory repair). It reviews evidence that some nonsteroidal antiinflammatory drugs (NSAIDs) and deafferentation of the unstable limb may accelerate cartilage loss in OA, and examines the relationship of synovitis and of changes in subchondral bone to the changes in articular cartilage.