Arthritis comprises over 100 different diseases and conditions. The most common is osteoarthritis. Other frequently occurring forms of arthritis include rheumatoid arthritis, lupus, fibromyalgia, and gout. Arthritis also affects children. A recent study estimated that 1 in 250 children has some form of arthritis or related condition.

Common symptoms include pain, aching, stiffness, and swelling in or around the joints. Some forms of arthritis, such as rheumatoid arthritis and lupus, can affect multiple organs and cause widespread symptoms.