Why your back hurts

Discomfort associated with specific causes of low back pain has reproducible characteristics. For instance, ruptured discs pressing on nerves cause pain that runs from the back to the lower leg and foot. The pain from muscle injuries in the back may spread across the low back but not lower than the buttock. Knowing where the pain initially starts and ends helps us make a good guess about the cause.

Mechanical disorders are caused by local problems in the bones, joints, tendons, ligaments, muscles, and nerves of the low back. Characteristically, being active or at rest has an effect on the intensity of the pain, either making it better or worse. The position of the spine also affects the degree of pain. If you have a disc herniation, you feel more pain when you sit, while people with spinal arthritis feel worse when standing. Most mechanical problems heal or improve with time, physical therapy, and medications. Only 1 to 2 percent of these mechanical difficulties call for surgical intervention, such as when they cause loss of bladder control or leg weakness.

Medical disorders cause symptoms throughout the body and are not limited to discomfort in the lumbar spine, and they don't get better or worse with activity or rest. In addition, many organs such as the kidneys, bladder, gastrointestinal system, lymph nodes, and major blood vessels fit up against the lower back (see fig. 1. 1). Diseases that affect these organs can cause back pain, with each organ system causing a certain kind of pain. When back pain originates in a structure other than the spine, the unique character of the pain can help doctors find the diseased organ system.