Orthopaedic surgeons are trained in the preservation, investigation, and restoration of the form and function of the extremities, spine, and associated structures by medical, surgical, and physical means. An orthopaedic surgeon is involved with the care of patients whose musculoskeletal problems include congenital deformities, trauma, infections, tumors, metabolic disturbances of the musculoskeletal system, deformities, injuries, and degenerative diseases of the spine, hands, feet, knee, hip, shoulder, and elbow. The orthopaedic surgeon manages special problems, diagnoses the injury or disorder, and establishes the treatment plan using surgery, medication, exercise, and/or physical therapy. They are also concerned with primary and secondary muscular problems and the effects of central or peripheral nervous system lesions of the musculoskeletal system. Orthopaedic surgeons treat patients of all ages, mostly on a short-term basis. Since many of their patients have been involved in accidents, orthopaedic surgeons also assess disability in legal actions. The field has undergone notable improvements in techniques and equipment, such as microsurgery and joint replacements. Their practice may be broad or limited to an area of special interest, such as hand surgery or sports medicine.