Back pain may occur in the upper, middle, or lower back; it is most often experienced in the lower back. It may originate from the bones and ligaments forming the spine, the muscles and tendons supporting the back, the nerves that exit the spinal column, or even the internal organs.
Back pain can range from mild, annoying discomfort to excruciating agony. Depending on how long it lasts, it can be described as acute or chronic. Acute back pain comes on suddenly but lasts only briefly, and is often intense. While chronic back pain is typically not as severe as acute back pain, it persists for a longer period and may recur frequently. The duration of acute back pain is a few days to a few weeks, with improvement during that time, whereas chronic back pain lasts for more than three months and often gets progressively worse.
The back is composed of bones, muscles, ligaments, tendons, and other tissues that make up the posterior, or back half, of the trunk extending from the neck to the pelvis. Running through and supporting the back is the spinal column, which forms a cage-like structure enclosing the spinal cord. Nerve signals directing movement travel from the brain to the limbs, while nerve signals transmitting pain and other sensations travel from the limbs to the brain. All nerve signals pass through the spinal cord. If the individual vertebrae stacked together to form the spinal column slide out of place, which is referred to as spondylolisthesis, pain may result as the bones rub against each other or as nerves entering the spinal cord are compressed.
Laurie Barclay, The Gale Group Inc., Gale, Detroit,