Rheumatoid arthritis (RA) is a form of arthritis that causes pain, swelling, stiffness and loss of function in your joints. It can affect any joint but is common in the wrist and fingers.

More women than men get rheumatoid arthritis. It often starts in middle age and is most common in older people. But children and young adults can also get it. You might have the disease for only a short time, or symptoms might come and go. The severe form can last a lifetime.

Rheumatoid arthritis is different from osteoarthritis, the common arthritis that often comes with older age. RA can affect body parts besides joints, such as your eyes, mouth and lungs. RA is an autoimmune disease, which means the arthritis results from your immune system attacking your body’s own tissues.

Treatments include medicine, lifestyle changes and surgery. These can slow or stop joint damage and reduce pain and swelling.

The cause of rheumatoid arthritis is not completely understood. The process involves inflammation and fibrosis of the capsule around the joints. It also affects the underlying bone and cartilage. RA can produce diffuse inflammation in the lungs, the membrane around the heart, the membranes of the lung, and whites of the eye. It can also produce nodular lesions, most common within the skin. It is a clinical diagnosis made mostly on the basis of symptoms and physical examination. X-rays, laboratory testing, and synovial fluid analysis might help support a diagnosis or exclude other diseases with similar symptoms.