Scope of the problem

Back pain affects up to 80% of the general population at some time during their lives. It is one of the most expensive outpatient diseases in medicine and is generally a recurrent problem. Most patients have no serious underlying disease and are termed “uncomplicated.” A few patients will have very serious disease necessitating emergent intervention. The process of identifying those with serious disease from the vast majority of patients with uncomplicated back pain can be difficult.

Anatomic essentials

Acute low back pain refers to pain felt in the lumbosacral spine and paraspinal areas. The pain may originate from lumbosacral structures such as bones (lumbar vertebrae, sacrum and coccyx), intervertebral discs, joints (facet, sacroiliac), soft tissues (muscles, tendons, ligaments), vascular structures, and nervous tissue (spinal cord, nerve roots). Low back pain may also be referred from pelvic, retroperitoneal, and abdominal structures due to shared innervation.

The spinal cord is housed in the spinal column, a series of interconnected bones held in place by complex ligamentous and muscular structures. The spinal cord is surrounded by the dura mater and a series of potential spaces. These spaces are important to clinicians because infection and tumor can seed there. The adult spinal cord ends at approximately the L1–L2 junction. The nerve roots at the end of the spinal cord are known as the cauda equina (horse's tail).