Back pain is one of humanity's most frequent complaints. In the U.S., acute low back pain (also called lumbago) is the fifth most common reason for physician visits. About nine out of ten adults experience back pain at some point in their life, and five out of ten working adults have back pain every year.

The spine is a complex interconnecting network of nerves, joints, muscles, tendons and ligaments, and all are capable of producing pain. Large nerves that originate in the spine and go to the legs and arms can make pain radiate to the extremities.

Underlying Causes

Muscle strains (pulled muscles) are commonly identified as the cause of back pain, as are muscle imbalances. Pain from such an injury often remains as long as the muscle imbalances persist. The muscle imbalances cause a mechanical problem with the skeleton, building up pressure at points along the spine, which causes the pain.

Another cause of acute low back pain is a meniscoid occlusion. The more mobile regions of the spine, such as the facet joints, have invaginations of their synovial membranes that act as a cushion to help the bones move over each other smoothly. The synovial membrane is well supplied with blood and nerves. When these become pinched or trapped sudden severe pain may result. The pinching causes the membrane to become inflamed, causing greater pressure and ongoing pain. Symptoms include severe low back pain that may be accompanied by muscle spasm, pain with walking, concentration of pain to one side, but no radiculopathy (radiating pain down buttock and leg). Relief should be felt with flexion (bending forward),and exacerbated with extension (bending backward).

When back pain lasts more than three months, or if there is more radicular pain (sciatica) than back pain, a more specific diagnosis can usually be made. There are several common causes of back pain: for adults under age 50, these include spinal disc herniation and degenerative disc disease or isthmic spondylolisthesis; in adults over age 50, common causes also include osteoarthritis (degenerative joint disease) and spinal stenosis,trauma, cancer, infection, fractures, and inflammatory disease. Non-anatomical factors can also contribute to or cause back pain, such as stress, repressed anger, or depression. Even if there is an anatomical cause for the pain, if depression is present it should also be treated concurrently.

New attention has been focused on non-discogenic back pain, where patients have normal or near-normal MRI and CT scans. One of the newer investigations looks into the role of the dorsal ramus in patients that have no radiographic abnormalities.