The lumbar spine may refer to the lower back or more specifically, the five vertebrae at the bottom of the spine. The lumbar spine includes these last 5 spinal discs, the discs between them, and the disc between the last lumbar spine (L5) and the sacrum (S1). Other structures associated with the lumbar spine include:
Though the cause of lower back pain is well known to be linked to degenerated lumbar-sacral discs in a high frequency of cases, injury or damage to any of these other structures could also be involved or the source of pain.
- The tendons and muscles that attach to the vertebral bones
- Facet joints that link each vertebra to the one above and below it
- Spinal ligaments
- The nerves and nerve roots that travel through to the lower leg, and those that combine with one another to make up the sciatic nerve
The lumbar spine gets the most attention in the medical literature, because it is back problems in this area that cause the most trips to the doctor and the most days missed off work. Most people suffering from back pain have lower back pain. The discs and joints of the lumbar spine support the majority of your body's weight, and if you are seated in a chair they are being compressed even as we speak. As you sit in your chair, the discs of your lower back, that are in roughly the shape of a hockey puck, are being pressed down between the solid vertebral bones. As these discs of your lower back become compressed, the composition of its gel-like interior allow this hockey puck shaped disk to bulge inwards and outwards. The discs actually begin to flatten and move outward during the course of a day, and to increase in height at night as they absorb water and nutrients from the surrounding blood vessels. This is one of the reasons why smoking and other lifestyle factors that decrease circulation can be linked to back pain.
If these discs lose their ability to absorb or retain water, or if their outer wall (annulus fibrosus) becomes torn, we may experience back pain for one of several reasons. We may directly feel discogenic pain as a result of the degeneration of a lumbar disc, or the herniation of the disc wall. Discogenic pain, or lumbar disc pain, is pain that is felt as a result of the breakdown of the disc. Exactly why some people have pain related to the destruction of the disc is not well understood, due to the fact that the intervertebral discs have not been thought to contain any nerve endings. Recently though, research findings have demonstrated that there are nerve endings in our discs which may respond to changes in the discs. We are more likely to experience lower back pain indirectly as a result of tears (herniation) in the outer rings of the disc, which allow the inner material of the nucleus to squirt through. When this inner material in the section known as the nucleus pulposus contacts the spinal ligaments, the spinal canal, or the nerve roots, then we may experience quite intense lower back pain, as well as pain and associated neurologic symptoms that radiate down the leg.
Other causes of pain in the lumbar spine include muscle strain from heavy lifting, sacroiliac joint dysfunction, spondylolisthesis, facet joint arthritis, and lumbar stenosis.