As we age, the intervertebral disc may lose water and become dried out. As this happens, the disc compresses. This may lead to the deterioration of the tough outer ring allowing the nucleus, or the inside of the ring, to bulge out. This is considered a bulging disc. As the disc continues to degenerate, or with continued stress on the spine, the inner nucleus pulposus may actually rupture out from the annulus. This is considered a ruptured, or herniated, disc. The fragments of disc material can then press on the nerve roots that are located just behind the disc space. This can cause pain, weakness, numbness, or changes in sensation. Most disc herniations happen at the lower lumbar spine, especially at the L4-5 and L5-S1 levels.

Lumbar disc disease is due to a change in the structure of the normal disc. Most of the time, disc disease comes as a result of aging and the degeneration that occurs within the disc. Occasionally, severe trauma can cause a normal disc to herniate. Trauma may also cause an already herniated disc to worsen.