Risk Factors and Causes of Degenerative Disc Disease
Degenerative disc disease typically is a result of the natural aging process, although it also can be caused by injury or trauma. At birth, intervertebral discs are about 80% water, along with collagen and proteins, with most of the water located in the nucleus pulposus. This fluid gives the disc its spongy quality and contributes to its shock-absorbing abilities.
Over time, the amount of water in the disc decreases and the collagens and proteins undergo chemical changes. As a result, the discs become more stiff and rigid, and therefore vulnerable to tearing. This process also causes the discs to flatten over time, reducing the amount of space between the vertebrae.
Pain associated with degenerative disc disease can be inflammatory and/or mechanical. Inflammatory pain is caused by the release of chemicals in the nucleus that irritate nerve endings in the annulus fibrosus. Mechanical pain is due to the physical compression of a nerve root as a result of herniation or disc space compression.
If a tear occurs in the outer ring of the disc, the soft inner nucleus can seep out and cause a bulge of the disc (herniation). This bulge may then compress one of the nerve roots in the spinal column, causing localized pain at the site of the nerve root. It also may cause pain that radiates along that nerve root’s pathway through the body (called radiculitis).
If a herniated disc occurs in the neck, pain may radiate to the back of the head, upper back, shoulders, and arms. Herniation in the lower back can cause pain in the buttocks, legs and feet.
Collapse of the disc and compression of the spine may create a condition called spinal stenosis, which is narrowing of the space available for the spinal cord and nerves. Spinal stenosis puts additional pressure on the nerves and can cause pain. It may also trigger a reaction in the spine that leads to the development of bone spurs—bony protrusions that further decrease the amount of available space.
Both inflammatory and mechanical pain also can cause muscle spasms and the impaired mobility associated with degenerative disc disease.
Signs and Symptoms of Degenerative Disc Disease
The primary symptom of degenerative disc disease is pain, which often worsens when sitting or standing and during certain types of activity (e.g., bending, lifting, twisting). In many cases, pain is relieved by changing positions, such as walking or swimming. Lying down can provide the best relief, as this takes all pressure off the spine.
Most people with degenerative disc disease experience chronic (persistent) neck or lower back pain with intermittent episodes of acute (sudden) pain. These acute episodes can last from a few days to a few months.
Degenerative Disc Disease Complications
Degenerative disc disease rarely leads to more serious conditions. However, patients who experience any of the following should seek immediate medical care:
- Pain that is getting worse or is disabling
- Leg weakness or pain, along with numbness or tingling
- Loss of bladder and/or bowel control