Causes of Degenerative Disc Disease

Degenerative disc disease can be associated with an injury to the back, or it may just be a sign of aging. Long before proof of degenerative disc disease, can be seen with imaging tests (computer aided views of your body), biochemical and cellular changes have already occurred; these degenerative changes happen gradually.

In the early phases of degenerative disc disease, spontaneous or post-traumatic tears, degeneration, fibrosis (hardening), and collapse of the disc may make it difficult for you to move your back freely. You may have low back pain and possibly leg pain if a nerve is squeezed; this feeling is frequently associated with degenerative disc disease.

Over time, the collagen (protein) structure of the annulus fibrosus changes. Additionally, water-attracting molecules—and hence water—in the discs decrease. Both of these changes reduce the disc’s ability to handle back movement.

As degenerative disc disease progresses, structures fold and buckle and bone spurs form. This can cause a narrowing of the space for the spinal cord and nerves—that disorder is called spinal stenosis. Stenosis can put pressure on the nerves in the low back. Below is an illustration of lumbar spinal stenosis.

Just like other parts of the body, each intervertebral disc has a nerve supply—the annular nerves. The inner gel-like nucleus pulposus does not have nerves, but the outer third of the annulus fibrosus does. When the disc tears or ruptures, chemicals are released, and they can irritate the nerves, causing inflammation and pain. However, it is possible to have an annular tear and have no symptoms.

In addition, herniation may put direct pressure on the nerves, causing pain in other parts of the body. This is known as radiculopathy. One area of nerves especially susceptible to injury is the cauda equina or “horse’s tail.” The cauda equina is a bundle of nerves located at lowest end of the spine, and it is made up of nerve roots and rootlets from the spinal cord above.