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INTRODUCTION

Patients with problems referable to the spine and extremities are classified by the type of symptom(s), 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 are acute, subacute, or chronic; when chronic, they may be slowly progressive. Describing the problem by symptom, site, acuity, aggravating or alleviating factors, and progression rapidly narrows the diagnostic possibilities. The exam then focuses on those specific body parts and signs.

When the problem is a single symptom in one location, the symptom, signs, and 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 are attributable to its bony structure and overlying muscles.

Bones

The ossified skeleton provides mechanical support for the body and protection for viscera within the body cavities, vertebral column, and skull. Mature bone forms by mineralizing 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 reapbsorption by osteoclasts and formation by osteoblasts is continuous. Bone must maintain enough strength to resist the compression and tension applied by mechanical loading 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 bones is affected during skeletal matuaration by the muscles pulling at their anatomic origins and insertions. 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.

Joints

Joints separate articulated bones. Fibrocartilage separates bones at joints where motion is minimal, e.g., the intervertebral discs. Synovial (diarthrodial) joints separate bones where motion is extensive. The bone surfaces of diarthrodial ...

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