A rheumatologist is an internist or pediatrician who received further training in the diagnosis (detection) and treatment of musculoskeletal disease and systemic autoimmune conditions commonly referred to as rheumatic diseases. These diseases can affect the joints, muscles, and bones causing pain, swelling, stiffness, and deformity. Autoimmune conditions occur when the immune system sends inflammation to areas of the body when it is not needed causing damage/symptoms. These diseases can also affect the eyes, skin, nervous system, and internal organs. Rheumatologists treat joint disease similar to orthopedists but do not perform surgeries. Common diseases treated by rheumatologists include osteoarthritis, gout, rheumatoid arthritis, chronic back pain, tendinitis, and lupus. Source: American College of Rheumatology