Sciatica is pain caused by irritation or pressure against the nerve roots of the sciatic nerve. People with sciatica usually have a shooting pain down the back of the leg. But they also may have leg weakness, tingling, or numbness.

The sciatic nerve is formed by the nerve roots coming out of the spinal cord into the lower back (lumbar region). The nerve goes down through the buttock, then its branches extend down the back of the leg to the ankle and foot.

Sciatica is usually caused by a bulging or ruptured (herniated) spinal disc that presses against one or more of the nerve roots that form the sciatic nerve. Pregnancy is also a common cause of the condition. Bone spurs (from arthritis or spinal stenosis), compressed nerve roots (usually a result of an injury), and certain rare tumours may also cause sciatica.

Symptoms may become worse from sitting, prolonged standing, or moving in ways that flex the spine (such as curl-ups and knee-to-chest exercises). Symptoms can also become worse from increased pressure from sneezing, coughing, having a bowel movement, or straining for a heavy lift or while labouring to deliver a baby. Symptoms may be relieved by walking, lying down, and moving in ways that extend the spine (such as press-ups).

Treatment depends on what is causing the nerve irritation. Heat or cold therapy (applying ice or a cold pack to the lower back) or physiotherapy is often used to help relieve pain.