Arthritis is a rheumatic disease that causes stiffness and pain in the joints, and may be accompanied by inflammation, redness and swelling. The two most common types of arthritis are osteoarthritis--which often occurs in older age and is characterized by pain in the fingers, knees and hips--and rheumatoid arthritis, which represents a problem with the body's defense system. People with rheumatoid arthritis often exhibit symmetrical inflammation of the joints, commonly in the hands and feet.