The normal spine viewed from the side forms a gentle "S" shape. When viewed from the back, the normal spine appears straight. The naturally occurring soft curves of the spine are designed to distribute mechanical stress in the body when at rest and during movement. When the curvature is even slightly abnormal, a person may experience occasional mild or annoying discomfort. If the curve is severely abnormal, the pain is usually severe and accompanied by disability. Scoliosis occurs in both children, where it is generally idiopathic, and adults, where it is often acquired.

An injury is a general term referring to damage to the body, and can be caused by accidents, falls, weapons, sports, and other incidents. Injuries may affect many parts of the body, including the brain, the extremities, and internal organs. Wounds are injuries that break the skin or other body tissues, and include cuts, scrapes, and punctured skin. This document is focused on injuries to the extremities and spine, referred to as musculoskeletal injuries throughout this document.