The phrase "a slipped disc" is used very commonly and indeed at some time of 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 fibrosus, together with some of the inner gelantinous nucleus pulposus, press on ligaments and nerves running close to the disc and produce pain. 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 of 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.

Although any disc in the entire spine can prolapse or burst, the most common ones to which this happens are the lowest two, that is between the fourth and fifth lumbar vertebrae and between the fifth lumbar and the top of the sacrum. 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. Prolapsed disc bursting backwards and to one side.
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. The pain of a prolapsed disc tends to be deep, dull and persistent and it may radiate into all sorts of unexpected places. For example, a prolapsed disc in the lower back may produce pain in several places such as the buttocks, hip or groin. Some people find that these pains are worse if they bend in one particular way. Others find that their pains become unbearable if they stand up straight. And it isn't uncommon for people to complain that their pain is worse when they sneeze, cough or laugh.

If you have prolapsed disc the first thing your doctor will want to do will be to make sure that your problem is caused by a disc that is misbehaving - and if it is a disc that is causing the trouble he or she will want to know which one.

If there is then any doubt, to investigate your back problem an orthopeadic (bone) surgeon and/or a neurosurgeon (nerves) will probably want to perform a number of investigations.

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

Other information can be found at:

Bulging Disc
Herniated Disc
Spine Dr.com