Prolapsed Intervertebral Disc (slipped disc) 

The lumbar spine is made up of 5 vertebrae each being separated by an intervertebral disc. The uppermost lumbar vertebrae is called L1 and the lowest is L5. The region above the lumbar is called the thoracic spine and the region below is the sacral area. 

The intervertebral discs act mainly as shock absorbers between the vertebrae and help the spine to move in a more flexible way. These discs are prone to damage over time through a process called degeneration. Small areas of weakness occur in the outer casing of the discs called fissures or tears and the central, more fluid part of the disc can herniate out. Discs can also become damaged following an acute incident such as lifting or bending incorrectly.

Most commonly discs will bulge or prolapse backwards due to the fact that flexion or forward bending activities put the discs at most risk. Think about the positions that you find yourself in during the day. More often than not people tend to be in flexed positions such as sitting at a desk, sitting in the car or slumped on the sofa. Prolonged poor sitting postures are just as stressful to the back as repetitive bending movements such as digging or moving heavy boxes. This is one of the reasons why we should sit up straighter and maintain a protective curve (inwards) in the small of our back.

When a disc prolapses posteriorly (backwards) it can come into contact with the spinal nerves as they exit the spinal canal. There is a bundle of spinal nerves which exit from either side of each adjoining vertebrae and irritation of these neural tissues can cause a variety of symptoms including pins and needles, numbness and muscle weakness. For example, the sciatic nerve originates from the L4 – S3 levels so a disc bulge or prolapse at any of these levels, which encroaches onto the nerve roots, will lead to sciatica type symptoms.

Chronic problems, which don’t respond well to physiotherapy, are often dealt with by an epidural injection of an anti-inflammatory steroid, which can be performed by a specialist. Your physiotherapist will be able to tell if you would benefit from this procedure and will be able to refer you to a suitable doctor.

N.B. A large central posterior disc prolapse can occasionally cause a serious condition called cauda equina syndrome. As the disc pushes backwards it can put pressure on the nerves which lead to the bladder or bowel. A loss of control of bladder or bowel function or any symptoms of altered sensation around the saddle area should be reported to a doctor without hesitation as prolonged compression can lead to irreversible changes.