Sciatica and sciatic nerve pain: causes and care

What sciatica means

The sciatic nerve is the largest nerve in the body. It is formed from nerve roots in the lower back, passes through the buttock, and runs down the back of the thigh. Near the knee it divides into two branches: the tibial nerve, which continues to the back of the calf and the sole of the foot, and the common peroneal nerve, which wraps around the outside of the knee and supplies the top of the foot.

“Sciatica” is not a diagnosis by itself. It describes a symptom: pain, and often tingling or numbness, that travels along this pathway. Doctors look for the reason the nerve or its roots are irritated.^[1,2]

When the source is the lower back

The most common cause is a pinched nerve root in the lower spine, often from a herniated disc or narrowing of the spinal canal. This is called lumbar radiculopathy. It usually causes pain that runs below the knee, often with numbness or tingling in part of the foot, and sometimes weakness.^[1,2] Spine specialists, primary care physicians and physical therapists usually lead the evaluation and care for this kind of sciatica. Our page on back or foot: finding the source of nerve pain explains how this differs from a nerve problem in the foot itself.

When the nerve is trapped in the buttock

In some people, the sciatic nerve is compressed after it leaves the spine. Deep gluteal syndrome is the term for a sciatic nerve problem that does not come from a disc and involves entrapment of the nerve in the deep gluteal space behind the hip.^[3] The older term “piriformis syndrome” is now considered one type of deep gluteal syndrome.^[4,6]

Features that clinicians look for include:

• pain in the buttock or back of the hip, sometimes with pain down the leg
• difficulty sitting for about half an hour
• tenderness deep in the buttock, and certain hip movements that bring on the pain^[3]

Causes in the deep gluteal space include injury, prior surgery, inflammation or infection, fibrous bands, problems with nearby muscles and tendons, and less often blood vessel problems or masses.^[4] In a review of surgical patients with this problem, the most common causes were iatrogenic (a result of previous treatment or surgery) at 30%, piriformis syndrome at 26%, and trauma at 15%.^[7]

When the sciatic nerve is injured

Injuries to the sciatic nerve cause weakness or numbness in the areas served by both the peroneal and tibial branches. In most injuries, the peroneal part is affected more than the tibial part, which can make a sciatic nerve injury look like a peroneal nerve problem near the knee.^[5] Most sciatic nerve injuries come on suddenly, such as after hip replacement, a hip fracture or dislocation. Some come from prolonged pressure on the nerve, such as during a long period of unconsciousness. Compression of the nerve by a mass or by the piriformis muscle is less common.^[5] If foot drop is present, see foot drop and common peroneal nerve compression.

How the cause is found

Evaluation begins with your history and a careful examination of the back, hip, leg and foot, including strength, reflexes and sensation. Depending on what is found, the next steps may include:

• MRI, which is the preferred imaging test for the deep gluteal space.^[4]
• Nerve studies (EMG and nerve conduction), which are used as nerve-specific tests.^[3] They are performed by another specialist. Read more in nerve testing for foot pain.
• A response to a diagnostic injection, which can help confirm a source in the buttock.^[4]

Treatment options

For deep gluteal syndrome, first-line care commonly includes physical therapy and medicines. When these are not enough, injections such as steroid or botulinum toxin are used, and surgery to release the nerve is considered last.^[6] A systematic review of surgery for the nerve in the deep gluteal space (481 patients in 28 studies, mostly small case series) reported improved pain in every study, with fewer major complications after endoscopic than open surgery. The quality of that evidence is limited.^[7]

For sciatica from a disc or spinal narrowing, the treatment plan is made with a spine specialist. Sciatic nerve injuries are evaluated for whether the nerve is likely to recover on its own and whether surgery to release, repair or reconstruct it could help.

Where a foot and ankle nerve evaluation fits

A nerve can be affected in more than one place. If your leg symptoms improve after treatment for the back or buttock but your foot pain, numbness or burning continues, a second pinch point in the leg or foot is worth looking for. It is also worth considering when symptoms follow a nerve path that does not fit the back. We can evaluate the peripheral nerves of the leg and foot and coordinate with your spine, hip and pain physicians.

When to seek care

Consider an evaluation if pain, numbness or tingling in your leg or foot lasts more than a few weeks, keeps coming back, or has not improved with treatment for your back.