The most common forms of arthritis are osteoarthritis and rheumatoid arthritis. In the US over 16 million people have osteoarthritis, and about 6 million have rheumatoid arthritis. Osteoarthritis is sometimes known as the wear-and-tear disease old age arthritis. It is solely a disease of the joints that occurs with increasing frequency with age, though it does affect people as early as age 35. It begins gradually and may remain mild for some time. There is usually little inflammation with this type of arthritis, and it does not cause general illness or affect parts of the body other than the joints. Disability often develops gradually.

Rheumatoid arthritis is inflammatory and attacks more than the joints. It may use disease in the lungs, skin, blood vessels, eyes, spleen, and heart. This is a type of arthritis that can cripple and even kill. It is a chronic disease, but in some cases acute spells occur when inflammation flares up unpredictably. About three times more women have this type than men. In children it may destroy joints and can affect the growth pattern.

Three other types of arthritis are much less common. Ankylosing spondylitis is a chronic inflammatory condition most common in men, which affects the spine and usually begins in the teens or early twenties. Systemic lupus erythermatosus (known as SLE or lupus) is an acute systemic disease related to rheumatoid arthritis. It causes inflammation and damage to joint and organs throughout the body.

Sometimes the kidneys, heart, lungs, brain, and blood vessels are affected by inflammation. A common feature of the disease is a skin rash on the face. Ten times mere women have SLE than men. Gout, or gouty arthritis, attacks and inflames any of the joints, one at a time. The most common site is the big toe. More men have it than women.