The term sciatica is often used to describe pain in the leg from a back problem. The name comes from the greek word ischion which means hip joint, after the area which the pain is often felt or was presumed to come from.
The term is often used inaccurately to decribe pain in the leg for any reason, however sciatica is very specific and usually caused by a specific and identifiable problem. Most leg pain is not sciatica.
What is sciatica?
True sciatica is a form of nerve root irritation, also called radicular (root) pain/irritation. This is a better term to use because nerve root irritations can occur in other parts of the body and these cannot be called sciatica. Sciatic pain is found in two main age groups, the younger adult and the older adult. The causes of the problem are different in the two groups.
Sciatica is severe leg pain which goes down the leg in a particular area, usually a clearly defined narrow strip of skin. There is no vagueness about the feeling. It is often sharp, shooting or surging in nature and worse below the knee and in the foot. It can be disabling and severe enough to badly disturb sleep. The sufferer may be forced to lie down as the pain is too severe to stand or sit.
How common is sciatica?
Sciatica is uncommon, much less common than back pain. In a large study Heliovaara reported the incidence of back pain over a lifetime to be 77% in men and 74% in women (people over 30), leg pain to be 35% and 45% respectively, and true sciatica only 5.3% in men and 3.7% in women.
What causes sciatica?
The cause of this type of pain is usually put down to ‘nerve trapping’ or more technically, to nerve root compression. However, experiments on nerves have shown that compression does not cause pain activity in a nerve, rather pins and needles and numbness.
However, when previously damaged nerve roots are squeezed or pulled, or nerve roots are stimulated electronically, then the normal sciatic type pain is produced. This is the specific shooting pain in a narrrow band which distinguishes this sort of pain from the aching, more vague referred pain which is much more common.
The most common cause of radicular pain is disc herniation, but it is becoming clear that this causes pain by other means than just compression. Some people can have disc herniation causing nerve compression on MRI scanning but do not have any symptoms, while others have recovered from sciatica but still show compression on MRI scan.
There is some evidence that inflammation has a part to play in this kind of pain. The central goo in the discs, the nucleus pulposus, may cause some form of chemical irritation of the nerve root.
This causes a series of changes: increased blood flow and swelling of the root which causes a block to conduction (messages cannot get through properly). Areas of the nerve can lose their blood supply, and eventually parts of the nerves can become fibrotic, ie scarred.
While this explanation does explain why nerve conduction should be affected, ie why muscle power and feeling may be altered, it does not explain why the pain occurs. This part of the sciatica puzzle is not yet complete.
Treatment of sciatica
Most people with sciatica recover without any specific medical treatment. Unlike what is recommended for low back pain, there may be a role for up to two weeks bedrest in someone with severe sciatica.
Rest should only be undertaken if the pain is so severe that being upright or sitting is only possible for very short periods, or activity badly worsens the pain. In these cases forcing oneself to keep going may not help the healing process. Even in these cases the person should still get up and about for short times as able.
There is no evidence that more than two weeks bedrest is helpful and it may become counterproductive if prolonged. Regular medication should be taken as advised by a medical practitioner.
As soon as the pain begins to settle the sufferer should increase the amount of activity he or she is doing by specific planned amounts every day. Pushing to get a job done or spending too long in one position may result in a worsening. Slow steady progress should be aimed for. Recovery may take a long period.
Surgery for sciatica
If the sciatic pain is exceptionally severe or the sciatica persists for longer than expected then a spinal surgical opinion may be sought. See spinal surgery for details of this approach.