Causes of Sciatica

It's important to understand what conditions cause sciatica because remember, sciatica is not a condition — it's a medical term used to describe symptoms caused by other low back conditions.

Several low back conditions can cause sciatica, including:

• Bulging disc or herniated disc: This is the most common cause of sciatica. When a disc bulges, the gel-like center (nucleus pulposus) pushes against the outer wall of the disc (annulus fibrosus). A herniated disc means that the nucleus pulposus breaks through the annulus fibrosus. With both bulging and herniated discs, the disc material can press on nerve roots, causing sciatica. The consequences of a herniated disc are worse than those of a bulging disc. The disc material that leaks out contains an acidic, chemical irritant (hyaluronic acid) that causes nerve inflammation.

• Degenerative disc disease (DDD): Sciatica is a common result of the aging process that affects discs called degenerative disc disease. DDD is a change in the disc shape and function, and it can result in a bulging disc or a herniated disc and pain.

• Piriformis syndrome: The piriformis muscle, located in the lower part of the spine, connects to the thighbone, and helps you rotate your hip. The sciatic nerve runs under the piriformis muscle, so muscle spasms can compress the sciatic nerve. It may be difficult to diagnose and treat as it is not easily identified by x-ray or MRI.

• Pregnancy: The extra weight and pressure on your spine caused by pregnancy can cause compression of the sciatic nerve. The symptoms will usually go away after childbirth.

• Spinal stenosis: Your nerves travel through passageways in your spine, and when this space narrows (stenosis), it can put pressure on the nerves in your low back.

• Spinal tumors and spinal infections: Although very rare, tumors and infections can compress the sciatic nerve.

• Spondylolisthesis: If a vertebra slips forward over the vertebra below it, it's called spondylolisthesis. This slip can pinch the nerve root and cause sciatica.

• Trauma: You can develop sciatica because of direct nerve compression from an outside force. For example, you could be injured in a car accident, resulting in a pinched nerve in your low back.