Lumbar Spine

The part of the spine that is in the lower back. The lumbar spine supports most of the body’s weight. It is made up of five individual bones called vertebrae, and each vertebra is separated from the next by a fibrous disk with a gel-like center. The bones are labeled, from top to bottom, L1 to L5. L1 connects with the bottom vertebra of the thoracic spine, which is in the middle back. L5 connects with the sacrum, a large triangular bone at the back of the pelvis that sits like a wedge between the two hip bones. The lumbar spine protects the nerves that control movement in the lower body.

Nearly everyone experiences lower back pain at some point in his or her life. While the most common cause of lower back pain is a muscle strain, problems in the lumbar spine can also cause lower back pain. The most common of these problems are as follows:

  • herniated disk
  • osteoarthritis
  • spinal stenosis
  • spondylolisthesis
  • osteoporosis
  • scoliosis

A herniated disk in the lumbar spine is a serious but rare problem in which the gel-like substance in the disks between two vertebrae pushes out and presses against the nerves in the spine. This can cause pain and weakness that is usually focused in one leg. It can be treated with nonsteroidal anti-inflammatory drugs (NSAIDs), controlled activity, or corticosteroid injections. Surgery is rarely needed.

Osteoarthritis (OA) of the lumbar spine affects the facet joints that connect the vertebrae. The facet joints are lined with cartilage. When the cartilage breaks down, the bones rub against each other, causing stiffness and pain in the lower back. Sometimes, the facet joints get bigger because little bits of bone called bone spurs form on them. If this happens, the spinal canal narrows, and this can pinch the nearby nerves.

Narrowing of the spinal canal is called spinal stenosis. OA is not the only possible cause of spinal stenosis. Other causes are a herniated disk, an injury, inflammatory arthritis such as rheumatoid arthritis (RA), or a genetic predisposition. When the narrowed spinal canal presses on the nerves that control the lower body, it can bring pain and numbness in the back, buttocks, and legs. More serious symptoms include loss of bowel and bladder control (a condition called cauda equina syndrome). Treatment for lumbar spinal stenosis often includes physical therapy and NSAIDs. Epidural steroid injections, which deliver corticosteroids directly to the spine, can also help ease pain. If these treatments are not effective, there are surgeries to remove bone and other tissues that are pinching the nerves (called decompression surgery) or, in more serious cases, to fuse some bones in the spine.

Spondylolisthesis occurs when a vertebra shifts out of place. This can be the result of injury or gradual degeneration. The symptoms of spondylolisthesis are similar to those of spinal stenosis. Treatments for spondylolisthesis are exercise, NSAIDs, braces, and, in some cases, surgery.

In osteoporosis, a person’s bones become less dense and are at increased risk of fracture. When fractures occur in the spine they are called compression fractures. About two-thirds of spinal fractures caused by osteoporosis involve the lumbar spine. People who have had compression fractures may not be aware of them at first, and pain (and poor posture) may arise gradually. Osteoporosis usually occurs after age 50 and is more common in women.

Scoliosis refers to a sideways curvature of the spine. Scoliosis usually develops in adolescents, most commonly in girls, though it can also occur later in life. It can affect the lumbar spine and the thoracic spine and is usually treated conservatively. In severe cases, however, surgery may be used.

Robert S. Dinsmoor is a medical writer and editor based in Massachusetts.

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