The phrase "a slipped disc" is used very commonly and indeed at some time or other this diagnosis has been blamed for producing almost every form of acute back pain. There are two major errors in this. First of all discs do not and cannot slip, and secondly what does go wrong and may be called a "slipped disc" is much less frequent than previously thought.

The correct term that should be used for patients with a "slipped disc" is a "prolapsed invertabral disc". What actually happens is that the disc bursts and fragments of the outer annulus fibrosis, together with some of the inner gelatinous nucleus pulposes, press on ligaments and nerves running close to the disc and produce pain.

A slipped disc, also called a prolapsed or herniated disc, occurs when one of the discs of the spine is ruptured (splits) and the gel inside leaks out. This causes back pain and as nerve damage can occur on the spinal cord pain may be felt in other areas of the body, most commonly in the legs

The term "slipped disc" is not only wrong but also harmful as it leads to a false idea of what is happening and therefore of the likely outcome. The mental picture produced is of a flat biscuit-like structure that slips sideways or backwards between the bones of the spine. If the disc can slip out in such a fashion then it could equally well slip back again and all should be well. The truth of the matter is that the disc bursts so that it is permanently damaged. Once this has happened, that disc will never be normal again. It's resistance to further injury is considerably reduced and anyone who has had a burst intervertebral disc is always at risk of further episodes of acute pain.

The lumbar (lower back) region of your spine bears most of the weight of the body and provides the most movement. It is made up of 5 bony vertebrae and each of these is separated by an intervertebral disc which acts as a shock absorber and prevents the vertebrae from rubbing together. Although any disc in the entire spine can prolapse or burst, the most common ones to which this happens are the lowest two, the fourth and fifth lumbar vertebrae and between the fifth lumbar and the top of the sacrum (L5/S1). Although the reasons for this are not entirely clear, the most likely explanation is that the stresses experienced by the spine are the greatest at these levels. Also the sacrum does not stand vertically but is tilted backwards, so producing a sharp curve in this region and giving a wedge shape to the discs. This wedge shape may concentrate the stresses in the back of the disc so making these lower lumbar discs particularly liable to damage. Briefly in a prolapse, the disc ruptures or bursts so that debris from the disc protrudes and can damage the surrounding structures. Most commonly these ruptures occur at the back of the disc but to one side or the other. These are known technically as the postero-lateral edges of the disc. Sometimes, however, the burst may occur directly backwards in the midline and this is known as a central posterior prolapse.

Because the discs themselves have virtually no nerve supply it is only when a disc prolapses and presses onto a nerve or some other vulnerable part of your spine that you will notice any symptoms.

Refer to the sections on - X-Rays, CT Scans, Myelography, Discography and Intevertebral Discs.

Other information can be found at:

Bulging Disc
Herniated Disc