Pain in the buttock and down the back of the leg, occurring when the sciatic nerve or its roots are compressed or damaged

  • Age, gender, and lifestyle as risk factors depend on the cause
  • Genetics is not a significant factor

Sciatica is a form of nerve pain that may be felt anywhere along the course of one of the sciatic nerves, the two largest nerves in the body and the main nerve in each leg. The sciatic nerves are formed from nerve roots in the lower part of the spinal cord. They run from the base of the spine down the backs of the thighs to above the knees, where they divide into branches that supply the front and back of the leg and foot. The pain of sciatica is caused by compression of or damage to the sciatic nerve, usually where it leaves the spinal cord. Many people have at least one episode of sciatica during their lives. Often, only one leg is affected. In most cases, the pain disappears gradually over about 1–2 weeks, but it may recur.

The sciatic nerves

Each sciatic nerve is formed from nerve roots in the spinal cord and runs down the leg to the foot. Sciatic pain may occur anywhere along the sciatic nerve and its branches.

What are the causes?

The most common cause of sciatica is a prolapsed or herniated disc in the spinal column that presses on a spinal nerve root. In older people, sciatica may be caused by changes in the spine as a result of various conditions, such as osteoarthritis. Women may develop sciatica during the last months of pregnancy because of posture changes that cause increased pressure on the sciatic nerve (see Common complaints of normal pregnancy). Muscle spasm and sitting in an awkward position for long periods of time are relatively common causes of brief episodes of sciatica in all age groups. Rarely, a tumour on the spinal cord may press on the sciatic nerve roots and cause sciatica.

What are the symptoms?

The symptoms can be mild or severe, with spasmodic or persistent pain in the affected leg. Symptoms may include:

  • Pain that is made worse by movement or by coughing.

  • Tingling or numbness.

  • Muscle weakness.

If sciatica is severe, you may have difficulty in lifting the foot on the affected side, and you may be unable to stand upright. Some people have difficulty in walking.

What might be done?

The doctor will examine you and test your leg reflexes, muscle strength, and sensation. You will probably be advised to continue your normal activities as much as possible but stop any activity that makes the pain worse. If the pain is severe, you may be advised to rest in bed for a day or two and be prescribed painkillers. If symptoms persist or if you have muscle weakness, you may have tests, such as MRI of the spine, to look for changes in the bones or a prolapsed disc.

Sciatica as a result of pregnancy will usually disappear after childbirth. Pain caused by muscle spasm or sitting awkwardly also tends to clear up without treatment. Occasionally, the condition can be helped by regular physiotherapy, exercise (see Preventing back pain). However, sciatica can recur. In some cases, surgery may be necessary to relieve pressure on the nerve, especially if there is weakness of the leg or foot muscles.

From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.

The subjects, conditions and treatments covered in this encyclopaedia are for information only and may not be covered by your insurance product should you make a claim.

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