Sciatica is a set of symptoms experienced in the area of the lower back, buttock, back of the leg and foot including tingling, numbness, weakness and/or pain. This usually occurs when one of five spinal nerve roots that make up the sciatic nerve, is compressed in the lower spine. Symptoms are typically experienced on one side only.

Causes of sciatica include:

Disc herniation: present in up to 90% of cases, this is the most common cause of sciatica. This occurs when a disc herniates and compresses the nerve roots where they exit the spine via a bone canal (intervertebral canal).

Spinal stenosis: narrowing (stenosis) of the spinal canal (a canal housing the spinal cord that runs through the centre of your spine) may compress the nerve roots. Spinal canal narrowing can be caused by spinal joint arthritis, bone spurs, spondylolithesis, inflammation, reduced disc height and/or herniated disc, which all may reduce the available space for the spinal cord and nerve roots to pass , thus pinching and irritating nerves from the spinal cord that travel to the sciatic nerves.

Isthmic spondylolithesis: a condition where one vertebral body has slipped forward on the vertebrae below, most commonly the fifth vertebrae on the sacrum) due to a small stress fracture in part of the bone that connects the body to the back of the vertebra.

Piriformis syndrome: in some individuals the sciatic nerve passes through the belly of a muscle located deep in the buttock. Muscle contracture may compress the sciatic nerve here.

Neural scar tissue: repetitive irritation of the sciatic nerve anywhere along its path may lead to a build up of scar tissue that may compress the sciatic nerve.