Arthritis is a joint disorder that involves inflammation of one or more joints. The inflammation may be triggered by infections in the joint or by autoimmune processes. In many of the arthritic conditions, such as osteoarthritis, the cause and process of the disease are not well understood.
Arthritis includes more than 100 different rheumatic diseases and conditions, the most common of which is osteoarthritis. Other forms of arthritis that occur often are rheumatoid arthritis, lupus, fibromyalgia, and gout. 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.
Arthritis is more common among adults aged 65 years or older, but people of all ages (including children) can be affected. Nearly two-thirds of people with arthritis are younger than 65. Arthritis is more common among women than men in every age group, and it affects members of all racial and ethnic groups. Arthritis is also more common among adults who are obese than among those who are normal weight or underweight.