Rheumatoid arthritis is an inflammatory disease that causes pain, swelling, stiffness, and loss of function in the joints. A normal joint (the place where two bones meet) is surrounded by a joint capsule that protects and supports it. Cartilage covers and cushions the ends of the two bones. The joint capsule is lined with a type of tissue called synovium which produces synovial fluid, a clear fluid that lubricates and nourishes the cartilage and bones inside the joint capsule. In rheumatoid arthritis, the immune system, for unknown reasons, attacks a person's own cells inside the joint capsule and causes inflammation (synovitis), resulting in the warmth, redness, swelling, and pain that are typical symptoms. During the inflammation process, the cells of the synovium grow and divide abnormally, making the normally thin synovium thick and resulting in a joint that is swollen and puffy to the touch. As these abnormal synovial cells begin to invade and destroy the cartilage and bone within the joint, the surrounding muscles, ligaments, and tendons that support and stabilize the joint become weak and unable to work normally.

The course of rheumatoid arthritis varies from person to person. For some people, it lasts only a few months or a year or two and goes away without causing any noticeable damage. Other people have mild or moderate disease, with periods of worsening symptoms, called flares, and periods in which they feel better, called remissions. Still others have severe disease that is active most of the time, lasts for many years, and leads to serious joint damage and disability.

Since there may be other scientific evidence that is not reported in the major U.S. biomedical databases, this list of treatments cannot be considered comprehensive.