Degenerative Disc Disease
Over time, daily motion and minor injuries put stress on the spine, creating wear and tear on the intervertebral discs, causing degenerative disc disease. The discs function like shock absorbers that act as a cushion during the body’s movement, keeping the spine flexible. Their role is vital to preserving the vertebrae since bones cannot sustain repeated stress without damage.
In a healthy intervertebral disc, the soft, spongy center (nucleus pulposus) contains a high level of water content that allows it to absorb stress. When excessive pressure or impact is incurred by the disc, the tough outer ligament material that surrounds the nucleus (annulus fibrosis) is often the first portion of the disc to exhibit damage. Small tears in the annulus fibrosis are replaced with scar tissue as the body tries to heal itself. However, the scar tissue is not as strong as the normal annulus fibrosis and weakens the annulus. As the annular fibrosis degenerates, the nucleus pulposus begins to loose water, causing it to dry up. If the annulus fibrosis becomes weak enough, the disc material can cause the annulus fibrosis to bulge (i.e. bulging disc) or rupture, i.e. herniated nucleus pulposus (HNP).
As a result of water loss, the disc loses its ability to absorb stress and act as a cushion for spinal flexibility. This situation creates more stress, and the damage cycle repeats, further tearing the annulus and causing the nucleus to collapse. As the disc compresses, the space between the vertebrae above and below it narrow. As the area becomes constricted, the facet joint at the back of the spine can move out of position, rendering the joint less operable. The facet joints become arthritic.
In addition to the lack of joint facilitation, bone spurs (osteophytes) may form around the disc space and the facet joint to impede excessive motion to the damaged spine area. If the bone spurs grow into the spinal canal and press on the spinal cord and nerves, they can crowd the spine, a condition known as spinal stenosis.