We studied the effects of joint movement and immobilization on acute and chronic calcium pyrophosphate dihydrate (CPPD) crystal induced arthritis in lapine knee joints. Exercised CPPD injected joints, in both acute (single 10 mg CPPD intraarticular (IA), duration: 5 h) and chronic (repeated 10 mg CPPD IA, duration: 20 and 42 days) experiments, demonstrated a more intense histologic synovitis compared to cast immobilized knees (p = 0.0001). In chronic experiments, both CPPD injected and noninjected immobilized knees showed greater cartilage histopathologic-histochemical abnormalities (p less than 0.004) and significant reduction in cartilage hexosamine content (p less than 0.005), compared to exercised joints. CPPD injected knees, both exercised and immobilized, demonstrated an initial phase of increased cartilage biosynthetic activity (35S incorporation) at 20 days, compared to noninjected knees (p = 0.02), followed by a decline at 42 days (p less than 0.005). Our data indicate that joint movement enhances acute and chronic experimental CPPD crystal induced synovitis. Articular cartilage is more adversely affected by joint immobilization than by chronic crystalline inflammation. An optimum balance between exercise and rest seems necessary for patients with arthritis so that cartilage can be preserved but pain from active inflammation also controlled.