Degenerative disc disease is a condition that involves weakening of one or more vertebral discs which normally act at the cushion between the vertebrae. This condition can develop as a natural part of the aging process but may also result from an injury to the back or neck. Degenerative disc disease typically begins when small tears appear in the disc wall called the annulus. For some people, these tears can cause pain. When the tears heal they create scar tissue that is not as strong as the original disc wall.
Over time, as the back is repeatedly injured, the process of tearing and scarring may continue weakening the disc wall. As people age, the nucleus pulposus (center of the disc) becomes damaged and loses some of its water content. This fluid is needed to keep the disc functioning as a shock absorber for the spine. If the nucleus pulposus is not able to act as a cushion, the nucleus collapses and the vertebrae above and below the damaged disc slide closer together. This improper alignment causes the facet joints (the areas where the vertebrae touch) to twist due to an unnatural position.
In time, this awkward positioning of the vertebrae may create bone spurs. If the bone spurs grow into the spinal canal, they may pinch the spinal cord and nerves, a condition called spinal stenosis. If the outer annulus tears and a piece of the nucleus pulposus moves through the tear, a disc herniation may pinch the spinal cord and nerves. The site of the injury may be painful. Some people experience pain, numbness, or tingling in the legs.