Acute low back pain will affect most adults at least once in their lives, yet nearly all will recover spontaneously, often without a precise diagnosis ever being made.

Most back pain is idiopathic, meaning that its exact cause is unknown. Many pa- tients with back pain have abnormalities that appear on imaging studies, such as osteoar- thritis or disk disease; however, many asymp- tomatic patients demonstrate radiographic findings. Therefore, it is incorrect to always assume a clear cause-and-effect relationship between symptoms and findings on imaging studies.

Low back pain can occur with or without leg pain. Pain that radiates down the back of the legs is known as radiculopathy or sciatica because the pain is thought to be caused by irritation of the roots of the sciatic nerve. Moreover, patients with back pain may have disk disease. Over time, aging and cumula- tive trauma may rob intervertebral disks of much of their ability to absorb shock. Spinal stenosis, characterized by bony or soft-tissue overgrowth in the spinal canal, may be the source of pain, especially in patients older than 60 years. Other sources of back pain include degeneration of the facet joints be- tween the vertebrae, inflammation of the surrounding soft tissues, or diseases of any of the nearby organs, such as the aorta or kidney. Although most back pain is benign and self-limiting, in some cases it is caused by diseases that require more aggressive treatment, such as tumors, infections, fractures, and instabilities.

Epidemiology

Back pain is an extremely common medical complaint, with a lifetime prevalence as high as 70%.1 It is estimated that at any given time 1% of the entire work force is disabled be- cause of back pain. Given its multiple causes, back pain has many associated risk factors. Heavy lifting at work has been cited by many, although many people who do not lift routinely have both back pain and disk damage. Weakness of the abdominal musculature may also increase the risk of back pain. Obesity, smoking, and depression are all associated with an increased risk of back pain.1