Intervertebral discs lie in between adjacent vertebrae in the spine. They are a cartilaginous joint, and allow movement of the vetebrae.

They consist of an outer annulus fibrosus, which surrounds the inner nucleus pulposus.

The nucleus pulposus is very fluid (like jelly), and acts like air in a pneumatic tyre. It can also shift slightly within the disc, depending on how the back is angled.

The annulus fibrosus consists of several layers of fibrocartilage, with the fibres of each layer running perpendicular its neighbours. (So it forms a criss-cross pattern). This is designed to be very strong.

As people age, the annulus fibrosus gets weaker, and the pulposus can herniate through it. This is called a slipped disc, and the nuclear pulposus may press against nerve roots, causing radicular pain .

There is one disc between each pair of vertebrae, increasing in size with the largest located at the base of the spine. As with vertebrae, there are 7 cervical, 12 thoracic, and 5 lumbar dics. A common problem often associated with a fall, car accident, or improper bending/lifting can result in the tearing, herniation (swelling), displacement (slippage), or shattering of these discs. Sometimes an afflicted person will feel pain only at the spot of the injury however others expierence other symptoms. All along the spine, bundles of nerves protrude out to different organs, tissues, extremities etc. It is very common in such injuries for the disc to press against these nerves (pinched nerve) causing radiating pain, numbness, tingling, diminished strength and/or range of motion. Any of these symptoms can be present alone or in various combinations. Often the afflicted individual will feel a sharp pain or numbness in their leg up to two feet from the spinal cord yet the cause is a pinched nerve in the lumbar region. The same is possible in the arms, hands, feet shoulders, neck and face. Discs can cause more severe issues when they pinch off nerves leading to organs. A common symptom of a lumbar disc injury is diminshed capacity of the bladder or bowel.

See also

• Lordosis