Intervertebral Discs

The intervertebral discs lie between the bones of the spine (the vertebrae) and make up approximately one quarter to one one third of the height of the spinal column. They form the joints of the spine and allow the spinal column to flex, bend and rotate. The outer part of the disc (the annulus fibrosus) is involved mainly in facilitating the movement of the spinal column, while the inner region (the nucleus pulposus) has primarily a weight-bearing role.

The mechanical functions of the disc depend on the properties of its extracellular matrix. The matrix of the disc is produced and maintained by a small number of disc cells. These cells both synthesis and breakdown the matrix. In a normal disc, synthesis and breakdown are balanced. The disc starts to degenerate when there is an imbalance between matrix synthesis and breakdown. Discs degenerate at a much earlier age than other tissues in the body.

Degenerate discs can be painful in themselves and/or can herniate ("slipped disc") leading to sciatica and low back pain. In the long term, degeneration can also lead to spinal stenosis (narrowing of the spinal canal). Scoliosis (curvature of the spine) can also initiate degenerative changes.