Patients with problems referable to the spine and extremities present in such a way that their condition can be classified rather rapidly by the following parameters: type of symptom(s), and its acuity, and its location(s). Symptoms are pain, tenderness, swelling, deformity, limited function (restricted motion, weakness), or unusual sensations like clicking and snapping. The symptoms are either localized to a single body part, affect two to four parts either simultaneously or sequentially, or are diffuse and either symmetrical or asymmetrical. Symptoms can be acute, subacute, or chronic; in the latter case they may be slowly progressive. Describing the problem by symptom, site, acuity, aggravating or alleviating factors, and progression can rapidly narrow the possibilities to be considered. The examination can then be focused on the specific body part and signs.
When the problem is a single symptom in a single location, the symptom, the signs, and the condition are inseparable and should not be thought of as separable descriptors. These will be addressed in the symptom, sign, or syndrome section depending, somewhat arbitrarily, on which is the key to diagnosis, the symptom, the sign, or the whole picture.
Traumatic injuries will be discussed at the end of the Syndrome section, organized by site of injury.
Major Systems and Their Physiology
The musculoskeletal system has four major functional components: bones and ligaments, synovial and fibrocartilaginous joints, muscles and tendons, and nerves innervating the muscles. Tendons anchor muscle to bone, whereas ligaments anchor bone to bone. The shape and body contour is attributable to its bony structure and overlying muscles.
The ossified skeletons provide mechanical support for the body and protection for the viscera within the body cavities, vertebral column, and skull. Mature bone forms by mineralization of osteoid laid down by osteoblasts on a cartilaginous matrix in the epiphyses of the long bones, endplates of the vertebrae and cartilaginous structures (endochondral bones of the skull and face). Cortical bone forms a thick cortex surrounding a central hollow, the marrow space. Trabecular bone forms an intricate lattice laid down along the lines of stress within the marrow cavity. Bone reabsorption by osteoclasts and new bone formation by osteoblasts is continuous. Bone must maintain strength sufficient to resist compression and tension applied by mechanical loading forces and muscle traction. Bone strength depends upon normal architecture, collagen, and mineralization; abnormality of any component results in susceptibility to fracture. The shape of mature bone is influenced by muscle pull at their anatomic origins and insertions during skeletal maturation. Muscles that insert on a small portion of bone and exert large forces deform the bone into prominences. Adjacent bones are connected by ligaments, collagenous bands continuous with the collagen of the bone itself. Ligaments stabilize the bones relative to one another and the intervening joints.