Sciatica causes and symptoms

Sciatica symptoms include back and leg pain but it is actually relatively uncommon. Sciatica causes back pain in only 5% of people. Confusingly the term sciatica is often used in layman’s terms to

describe any lower back pain. It is far more likely 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 vertebra 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 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.

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

sciatica causes and symptoms 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

sciatica causes

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.

Spinal stenosis

this is a condition where the spinal canal becomes narrowed and this can lead to nerve root irritation.

Spinal disc disease

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.