Joint disease, any of the diseases or injuries that affect human joints. Arthritis is no doubt the best-known joint disease, but there are also many others. Diseases of the joints may be variously short-lived or exceedingly chronic, agonizingly painful or merely nagging and uncomfortable; they may be confined to one joint or may affect many parts of the skeleton. For the purposes of this article, two principal categories are distinguished: joint diseases in which inflammation is the principal set of signs or symptoms and joint diseases, called noninflammatory in this article, in which inflammation may be present to some degree (as after an injury) but is not the essential feature.
Arthritis is a generic term for inflammatory joint disease. Regardless of the cause, inflammation of the joints may cause pain, stiffness, swelling, and some redness of the skin about the joint. Effusion of fluid into the joint cavity is common, and examination of this fluid is often a valuable procedure for determining the nature of the disease. The inflammation may be of such a nature and of such severity as to destroy the joint cartilage and underlying bone and cause irreparable deformities. Adhesions between the articulating members are frequent in such cases, and the resulting fusion with loss of mobility is called ankylosis. Inflammation restricted to the lining of a joint (the synovial membrane) is referred to as synovitis. Arthralgias simply are pains in the joints; as ordinarily used, the word implies that there is no other accompanying evidence of arthritis. Rheumatism, which is not synonymous with these, does not necessarily imply an inflammatory state but refers to all manners of discomfort of the articular apparatus including the joints and also the bursas, ligaments, tendons, and tendon sheaths. Inflammation of the spine and joints is called spondylitis.