The sciatic nerve is the largest single nerve in the human body; it runs from each side of the lower spine through deep in the buttock into the back of the thigh and all the way down to the foot. It serves a vital role in connecting the spinal cord with the leg and foot muscles.

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.

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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 radiculopathy, or radicular pain, indicating that the symptoms originate with a radicular nerve in the spine.

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.

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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 a herniated disc. The nerve roots that exit the spine to form the sciatic nerve are extremely sensitive, and the inner portion of the disc that may herniate or extrude contains proteins that are inflammatory and easily irritate the nerve.

See All about L5-S1 (Lumbosacral Joint)

See Lumbar Herniated Disc: What You Should Know

When this happens, pain radiates into the rear and back of the thigh and calf, and occasionally may extend down to the foot. Numbness, tingling, and/or a burning or prickling sensation are also common sciatica symptoms.

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 (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

  • See Lumbar Radiculopathy

  • 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.

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 (e.g. a herniated disc).