Rheumatology is the study of rheumatic illnesses, especially arthritis. A rheumatologist is a physician who diagnoses and treats arthritis and other conditions associated with joints, muscle, bones and tendons. This physician specializes in non-surgical treatment of diseases, and works with patients who have unexplained conditions such as weakness, fever, fatigue and weight loss. The rheumatologist also treats patients with lupus, scleroderma, gout, vasculitis, fibromyalgia and other disorders.