Rheumatoid arthritis (RA) is a chronic autoimmune disorder that primarily affects the joints, causing inflammation, pain, and stiffness. Unlike osteoarthritis, which results from wear and tear on the joints, RA occurs when the body's immune system mistakenly attacks healthy tissue, particularly the synovium—the lining of the joints. This leads to swelling, joint damage, and, if left untreated, can result in deformities and loss of function. RA typically affects joints on both sides of the body, such as the hands, wrists, knees, and feet. Early symptoms may include fatigue, mild fever, and joint tenderness, followed by swelling and restricted movement. While the exact cause of RA is unknown, genetic factors, infections, and environmental influences are believed to contribute.

Treatment aims to reduce inflammation, relieve pain, and prevent joint damage. Common therapies include medications, and in some cases, surgery, to manage symptoms and improve quality of life.