Sciatica Causes
Sciatica causes back and leg pain but it is actually relatively uncommon. Only 5% of you will have true sciatica. Confusingly the term sciatica is often used in layman’s terms to describe any lower back pain. Far more of you will have simple lower back pain.
True sciatic back pain is caused by an irritation of the sciatic nerve. This irritation is usually caused by a disc bulge.
The Sciatic Nerve
The spine is made up of large bones called vertebrae and these are separated from one another by spinal discs. In the lower back these discs are large and they act as shock absorbers between the vertebrae.
The Spinal Cord
The spinal cord runs down the centre of the spine and splits into nerve roots at each vertebral level, these nerve roots exit the spine, one on either side of each vertebra.
Nerve Roots Leaving the Spine
These nerve roots then bundle together outside the spine to form large nerves. In the legs there are two main bundles of nerves.
- The nerve running down the back of your thigh and calf is called the sciatic nerve (not the sciatica nerve - sciatica is the pain from the nerve).
- The one running down the front is called the femoral nerve.
Disc Bulges and Sciatica
Sometimes, the central area of the disc, the nucleus, shifts slightly in one direction or the other (nearly always backwards and to the side) and causes a bulge in the outside wall of the disc. This bulge can cause inflammation and irritation of the nerve.
A Disc Bulge Irritating a Nerve Root
Sometimes, the bulge becomes very severe and you can get a herniated disc and back pain.
In severe cases it can cause the nerve to become ‘trapped’ or pinched.
This is often called a ‘slipped disc’ but in reality discs can't slip, they are firmly fixed above and below.
There are a few, much less common sciatica causes:
- Spondylolisthesis
This is a movement of one vertebra on the other which can irritate the sciatic nerve.
this is a condition where the spinal canal becomes narrowed and this can lead to nerve root irritation.
Years of changes to the disc can lead to it becoming dehydrated and less ‘fat’ with water. The discs degenerate with age. If the condition is severe enough it can lead to nerve root irritation, sciatica and back pain.
These are unusual but read this section on red flags and serious back problems.
More on the symptoms that sciatica causes
More Sciatica Symptoms - Severe Lower Back Pain Problems
Lower Back Pain Toolkit Home Page
14-Sep-2009
