Degenerative joint disease (DJD), or arthritis, affects the smooth articular cartilage of the joint, which is the covering of bone in the joints that is responsible for the smooth, non-painful motion of joints. When it becomes worn, raw bone surfaces become exposed and rub together. DJD is the result, causing pain and lack of joint mobility.

DJD can occur over a lifetime of wear or as a result of injury. The soft tissue lining of the joint (synovium) is the first tissue in many animals to be affected in the disease and the subsequent irritation of the joint lining (synovitis) liberates chemical mediators that have been shown to be responsible for cartilage degeneration.

Primary cartilage damage can also initiate a cascade of events that result in further cartilage damage and synovial lining inflammation. This results in a vicious cycle of cartilage degeneration, release of degenerative factors and continued cartilage degeneration.

Normal cartilage is composed of cartilage cells (chondrocytes) and a supporting substance (matrix) that is produced by the cells. DJD involves the derangement of chondrocyte metabolism and subsequent matrix alteration.

What to Watch For

Lameness

Swollen joints

Muscle atrophy

Dry crackling sound upon movement of the joint (crepitation)