Rheumatoid arthritis (RA) is a systemic disease that attacks multiple joints throughout the body. About 90 percent of people with RA eventually develop symptoms related to the foot or ankle. Usually symptoms appear in the toes and forefeet first, then in the middle and back of the foot, and finally in the ankles. Other inflammatory types of arthritis that affect the foot and ankle include gout, ankylosing spondylitis, psoriatic arthritis, and Reiter's syndrome.
The exact cause of RA is unknown but there are several theories. Some people may be more likely to develop RA because of their genes. However, it usually takes a chemical or environmental trigger to activate the disease. In RA, the body's immune system turns against itself. Instead of protecting the joints, the body produces substances that attack and inflame the joints.