Degenerative disc disease begins when small tears appear in the disc wall, called the annulus. These tears can cause pain. When the tears heal, they create scare tissue that is not as strong as the original disc wall. If the back is repeatedly injured, the process of tearing and scarring may continue, weakening the disc wall.
Over time, the nucleus (or center) of the disc becomes damaged and loses some of it's water content. This center is called the pulposus and it's water content is needed to keep the disc functioning as a shock absorber for the spine.
Unable to act as a cushion, the nucleus collapses. The vertebrae above and below this damaged disc slide closer together. This improper alignment causes the facet joints - the areas where the vertebral bones touch - to twist into an unnatural position. In time, this awkward positioning of vertebrae may create bone spurs.
If these spurs grow into the spinal canal. the may pinch the spinal cord and nerves (a condition called spinal stenosis)
The site of injury may be painful. Some people experience pain, numbness or tingling in the legs. Strong pain tends to come and go. Bending, twisting, and sitting may make the pain worse. Lying down relives pressure on the spine.