Each vertebra of the spine is cushioned by spongy intervertebral discs. A healthy disc acts as the shock absorber for the spine. If the disc is injured, it may bulge outwards or rupture. This is known as having a herniated disc.

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Herniations within the discs may be caused by:

• Injury to the spine can cause tears within the outer layers of the discs. Once the outer layers tear, the inner gelatinous core begins to press outwards and forms a bulge or herniation.

• Normal wear and tear over the years can also cause herniations. This is in large part due to a gradual decrease in fluid within the discs as we age. They begin to lose their cushion and flexibility.
   

After the disc herniates, it then can begin pressing on the spinal nerves or nerve roots. This can cause pain, numbness, tingling, and weakness along the path of the affected nerve. A lower back disc herniation can radiate symptoms down one or both legs depending on the nerves that are being affected. The sciatic nerve is the most common nerve involved with a lumbar herniation. The term sciatica is used to describe the distribution of pain down the legs along the sciatic nerve.