As rheumatoid arthritis progresses, these abnormal synovial cells begin to invade and destroy the cartilage and bone within the joint. The surrounding muscles, ligaments, and tendons that support and stabilize the joint become weak and unable to work normally. All of these effects lead to the pain and deformities often seen in rheumatoid arthritis. Doctors studying rheumatoid arthritis now believe that damage to bones begins during the first year or two that a person has the disease. This is one reason early diagnosis and treatment are so important in the management of rheumatoid arthritis.
Some people also experience the effects of rheumatoid arthritis in places other than the joints.
About one-quarter develop rheumatoid nodules. These are bumps under the skin that often form close to the joints. Many people with rheumatoid arthritis develop anemia, or a decrease in the normal number of red blood cells. Other effects, which occur less often, include neck pain and dry eyes and mouth. Very rarely, people may have inflammation of the blood vessels, the lining of the lungs, or the sac enclosing the heart.