Inflammation of the membrane lining a joint (see JOINTS). It is usually painful and accompanied by effusion of fluid within the synovial sac of the joint. It is found in RHEUMATOID ARTHRITIS, various injuries and inflammations of joints, and in the chronic form in TUBERCULOSIS. Treatment of synovitis is with rest, splinting, ANALGESICS and NON-STEROIDAL ANTI-INFLAMMATORY DRUGS (NSAIDS). Infection should be treated with ANTIBIOTICS. If the joint fails to respond, surgery (SYNOVECTOMY) may be needed. (See also JOINTS, DISEASES OF.)