RA is an autoimmune disease, a disorder caused by the body's tissues being attacked by it's own immune system, which results in swelling and inflammation of the joints. This inflammation can severely inhibit movement and cause pain in the areas of the afflicted joint. While joint pain and inflammation are the most commonly known side effects of this disease it can also afflict pain on tendons, muscles, and ligaments. In some cases infections and organ damage are also side effects of RA.