The sciatic nerve is the largest type of nerve in the human body. Every person has two sciatic nerves, which run from each side of the lower spine through deep in the buttocks, into the back of the thighs, and all the way down to the feet. Sciatic nerves serve a vital role in connecting the spinal cord with the muscles of the legs and feet.

The sciatic nerve is the longest and largest nerve in the human body. It runs from the lower back through the back of the leg, and down to the toes. Watch: Sciatic Nerve Anatomy Video

Any type of pain and/or neurological symptoms that are felt along the sciatic nerve is referred to as sciatica.

See What You Need to Know About Sciatica

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How the Sciatic Nerve is Affected

Sciatica is commonly caused by some type of compression of a spinal nerve in the lower back. The medical term for sciatica is lumbar radicular pain, indicating that the symptoms originate at the nerve root. Nerve roots, sometimes called radicular nerves, are located where nerves branch out from the spine. These roots exit the left and right sides of the spinal column through spaces between vertebrae.

See Radiculopathy, Radiculitis and Radicular Pain

The specific symptoms will be different depending on which spinal nerve is affected and how much it is compressed.

Herniated discs, bulging discs, and sciatica
A variety of lower back problems can lead to pain that radiates along the sciatic nerve. Most often, sciatica pain is caused when the L5 or S1 nerve root in the lower spine is irritated by disc-related causes:

  • Herniated discs. When a disc is herniated, its tough fibrous outer shell has broken, causing its inner contents to leak out. The interior, called the nucleus pulposus, is a mixture of water, collagen, and proteins. When the proteins come into direct contact with the sciatic nerve, the nerve becomes irritated and inflamed. The term, “chemical pain” is often used to describe the symptoms associated with this process.

    See Lumbar Herniated Disc: What You Should Know

  • Bulging discs. A bulging disc can also irritate the sciatic nerve root. In these cases, the nucleus pulposus remains contained in the disc. However, the disc’s outer shell is weakened in one or more areas, causing it to protrude. The protrusion(s) can put pressure on the nearby sciatic nerve root.

See Sciatica Causes

A herniated or bulging disc can cause pain to radiate into the back of the buttock, thigh, and calf. Occasionally, pain may extend down to the foot. Numbness, tingling, and/or a burning or prickling sensation are also common sciatica symptoms. Weakness in specific muscles may also occur in certain cases.

See Leg Pain and Numbness: What Might These Symptoms Mean?

Common Symptoms of Sciatic Nerve Compression

The most common form of leg pain from the sciatic nerve is characterized by the following symptoms:

  • Occurs in one leg (usually not both)
  • Starts in the low back or buttock and radiates down the back of the thigh and typically into the lower leg and/or the foot
  • Is usually experienced as a sharp pain, as opposed to a throbbing or dull ache. Words people often use to describe sciatic nerve pain include burning, searing, sharp, or electric-like pain
  • Is usually worse when standing or sitting still, and feels better lying down or walking
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In addition to pain, other common symptoms include pressure, numbness, tingling, or a prickling sensation that radiates down the leg. Leg or foot weakness may also be present.

See Causes of Leg Pain and Foot Pain

Sciatica is actually a symptom, not a diagnosis. The term literally means that a patient has pain down the leg resulting from compression of the sciatic nerve. The diagnosis is what is causing the compression (such as a herniated disc).

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