Orthopedics is the study of the musculoskeletal system. Orthopedic doctors help patients with the diagnosis, prognosis and treatment of problems associated with the bone, joints, ligaments, tendons, muscles, and nerves of the body. Orthopedics is one of many medical specialties. Joint replacement surgery replaces damaged joints or resurfaces damaged bones in a joint to create new joint surfaces. Learn more about the most common types of joint replacement surgery.