Rheumatology is a subspecialty of internal medicine dealing with diseases of joints, muscles, bones, and tendons. Rheumatic diseases encompass more than 100 discrete disorders, some with multisystem involvement, and many with a wide variety of clinical manifestations and outcomes. The rheumatologist diagnoses and treats both chronic and acute conditions, including arthritis, systemic rheumatic diseases, back pain, gout, lupus, bursitis, muscle strains, collagen and other soft-tissue diseases, and athletic injuries. Because these diseases are often difficult to diagnose and treat, the rheumatologist's orientation is toward cognitive skills. It is important for rheumatologists to have a good background in biochemistry, immunology, radiology, internal medicine, neurology, orthopaedics, psychiatry, and rehabilitative medicine.