Second most common is rheumatoid arthritis, which affects 2.5 million Americans. It can strike at any age, but usually appears between ages 20 and 50. The hands are most commonly affected, but it can affect most joints of the body. Inflammation begins in the synovial lining and can spread to the entire joint. Highly variable and difficult to control, the disease can severely deform joints.
Some people become bedridden.
Others continue to run marathons. An autoimmune disease affecting the whole body, rheumatoid arthritis can also cause weakness, fatigue, loss of appetite, muscle pain, and weight loss. In about one in six, the disease becomes severe and can shorten life. Researchers hope to find ways to predict which patients should be treated more aggressively. Cartilage covers the bone ends, absorbing shocks and keeping the bones from rubbing together when the joint moves.