Sciatica Causes

By: Stephen H. Hochschuler, MD

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Sciatica refers to a set of symptoms which are usually caused by a problem in the lower back called a radiculopathy—when a nerve root that connects to the sciatic nerve is compressed or irritated. Common low back problems and other spinal conditions that can cause sciatica include:

Lumbar herniated disc. A herniated disc occurs when the soft inner core of the disc (nucleus pulposus) extrudes or “herniates” through the fibrous outer core (annulus) of the disc, irritating the contiguous nerve root as it exits the spine.In general, it is thought that a sudden twisting motion or injury can lead to an eventual disc herniation and sciatica.However, most discs weaken due to repetitive stress and the final result is a herniation. A herniated disc is sometimes referred to as a slipped disk, ruptured disk, bulging disc, protruding disc, or a pinched nerve and sciatica is the most common symptom of a lumbar herniated disc.

See also Lumbar disc herniation

In This Article:

What You Need to Know About Sciatica

Sciatica Causes

Sciatica Symptoms

Sciatica Treatment

Sciatica Surgery

Practical point:
Treatment of sciatica requires a diagnosis of the underlying cause of the sciatica pain.

Lumbar spinal stenosis. This condition commonly causes sciatica due to a narrowing of the spinal canal. Spinal stenosis is more common in adults over age 60. Lumbar stenosis typically results from a combination of one or more of the following: enlarged facet joints, overgrowth of soft tissue, and a bulging disc placing pressure on the nerve roots as they exit the spine and causing sciatica.

See also Definitive Guide to Lumbar Spinal Stenosis

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Degenerative disc disease. While disc degeneration is a natural process that occurs with aging, in some cases one or more degenerated discs can also irritate a nerve root and cause sciatica. Degenerative disc disease is diagnosed when a weakened disc results in excessive micro-motion at the corresponding vertebral level and inflammatory proteins from inside the disc become exposed and irritate the area (including the nerve roots).

See also Degenerative disc disease

Isthmic spondylolisthesis. This condition occurs when a small stress fracture allows one vertebral body to slip forward on another vertebral body (e.g. the L5 vertebra slips over the S1 vertebra). With a combination of disc space collapse, the fracture, and the vertebral body slipping forward, the L5 nerve can get pinched as it exits the spine and cause sciatica.

See also Isthmic spondylolisthesis

Piriformis syndrome. The sciatic nerve can also get irritated as it runs under the piriformis muscle in the rear. If the piriformis muscle irritates or pinches a nerve root that comprises the sciatic nerve, it can cause sciatica-type pain. This is not a true radiculopathy (the clinical diagnosis of sciatica), but the leg pain can feel the same as sciatica caused by a nerve irritation.

See also Piriformis syndrome—another irritation to the sciatic nerve

Sacroiliac joint dysfunction. Irritation of the sacroiliac joint at the bottom of the spine can also irritate the L5 nerve, which lies on top of it, and cause sciatica-type pain. This is not a true radiculopathy, but the leg pain can feel the same as sciatica caused by a nerve irritation.

See also Sacroiliac Joint Dysfunction

It is important to know the underlying clinical diagnosis of the cause of sciatica, as treatments will often differ depending on the cause. For example, specific sciatica exercises are different depending on pathology causing the sciatica symptoms.