Over time, as degeneration (wear and tear) occurs, the intervertebral disc can lose its flexibility, elasticity and shock absorbing characteristics. The tough fibrous wall of the disc may then weaken and split and no longer be able to contain the gel-like substance in the centre. This material may bulge or push out through a tear in the disc wall (herniation), causing pain when it touches a nerve (sciatica). A nerve is like an electrical wire. It tells your muscles to move and tells your brain information about various sensations such as pain, temperature, light touch, pressure sensation and the position of your legs. Lumbar nerve root pain can go below the knee, as far as the foot and is felt in the area of the leg that the particular spinal nerve supplies.

The most common nerve to be irritated is L5 and pain is typically felt along the outside of the calf and sometimes across the top of the foot. Symptoms also associated with sciatica include altered sensation, pins and needles, burning, numbness or even weakness of the muscles in the leg that the nerve supplies.

Very few people who have a lumbar disc prolapse need surgery. It is unusual to operate before 6–12 weeks because a significant number of people do get better naturally. This can happen if the disc or swelling around a nerve decreases naturally (with time) or is helped by image-guided steroid injection. Six out of 10 patients will get better spontaneously after six weeks. Other than for signs of nerve damage, surgery is usually only considered by a doctor when the pain is very bad and has not got better with strong pain relief after this time.

There is a balance of waiting while nature gets you better, versus waiting too long which might prolong your suffering and pain or compromise nerve function (weakness, numbness or pain recovery). In rare cases the nerves which control your bladder, bowel and sexual function can be compressed. This is known as cauda equina syndrome(CES) and often requires urgent surgical intervention. Fortunately, immediate spinal surgery is only necessary in a few cases.