Rheumatoid arthritis is a common, persistent systemic disorder that can cause inflammation of joints throughout the body. Joints contain a number of structures that allow for ease of movement. The ends of the bones in a joint are protected from rubbing together by an elastic cushioning material, known as cartilage. The entire joint is surrounded by a capsule, known as the synovial sac. A thin layer of tissue (synovial membrane) lines the sac and secretes synovial fluid, which provides lubrication to ease movement.

In the early stage of rheumatoid arthritis, the synovial membrane becomes inflamed and thickened, causing pain and limiting joint movement. As the disease progresses, the cartilage and the ends of the bones erode. The result is severe joint damage and deformity. Joint pain is often preceded by general, nonspecific symptoms, such as fever, fatigue, and loss of appetite. It may also be prefaced by stiffness in the joints, particularly in the morning.

The hallmark of the disorder is involvement of the small joints of the hands and wrists with painful, warm, swollen, tender, and reddish joints. The process can also involve the elbows, shoulders, knees, hips, ankles, feet, and neck. Symptoms tend to occur symmetrically; that is, joints on both sides of the body are usually affected at the same time. In some cases other organ systems of the body-including the eyes, heart, and lung-may become inflamed too. Symptoms occur in lengthy episodes that may be separated by remission periods of reduced or total absence of pain and stiffness. Between 50 and 75 percent of patients experience a remission within one to two years after the first episode.

Current research suggests that rheumatoid arthritis is an autoimmune disorder caused by an attack of the immune system on some of the body's own cells. The disease usually develops between the ages of 20 and 50, and its prevalence increases with age. Women are affected approximately three times more frequently than men. Treatment is aimed at relieving pain and inflammation, preventing joint deformity, and preserving function.