This type of arthritis affects over 2 million Americans. It's an autoimmune disease in which the body's immune system causes joint linings to become inflamed, leading to pain and loss of movement.

Rheumatoid arthritis tends to affect women more than men. According to NIAMS, it also has several features that make it different from other kinds of arthritis. For example, rheumatoid arthritis generally occurs in a symmetrical pattern. This means that if one knee or hand is involved, the other one is also. The disease often affects the wrist joints and the finger joints closest to the hand. It can also affect other parts of the body besides the joints. It can affect the spine but it happens less often than with osteoarthritis. In addition to pain and swelling of the joints, people with the disease may have:

• fatigue
• occasional fever
• a general sense of not feeling well (malaise)

The inflammation caused by rheumatoid arthritis is often unpredictable and hard to control. The Arthritis Foundation says this is the most crippling form of arthritis, and that it can flare up, and then go into remission. Rheumatoid arthritis can also lead to deformities in the joints.