Sciatic nerve

Nervus ischiadicus

Formed from the L4-S3 nerve roots of the sacral plexus. It exits the pelvis through the greater sciatic foramen below the piriformis muscle. It descends through the posterior thigh, dividing into the tibial and common peroneal (fibular) nerves, usually at the popliteal fossa.

Type Nerve
Body System Nervous
Body Region Hip
Parent Structure nerve
Latin Name Nervus ischiadicus
FMA ID 19034

Function

The largest and longest nerve in the body, providing motor innervation to the posterior thigh and all muscles below the knee. Provides sensory innervation to the lateral leg, foot, and parts of the posterior thigh.

Clinical Significance

Sciatica (sciatic nerve irritation, often from disc herniation) causes radiating pain down the posterior leg. Piriformis syndrome compresses the nerve in the buttock. Improper gluteal injections can damage the nerve. Complete sciatic nerve injury causes loss of all movement below the knee.

Frequently Asked Questions

What does the sciatic nerve do?
The sciatic nerve is the largest and longest nerve in the human body. It provides motor innervation to most muscles of the posterior thigh and all muscles of the lower leg and foot. It also carries sensory information from the skin of the lower leg, foot, and part of the thigh back to the spinal cord.
Where is the sciatic nerve located?
The sciatic nerve forms from nerve roots L4 through S3 in the sacral plexus. It exits the pelvis through the greater sciatic foramen, typically below the piriformis muscle, and runs deep in the posterior thigh between the hamstring muscles. At the popliteal fossa behind the knee, it divides into the tibial nerve and common fibular nerve.
What causes sciatica?
Sciatica refers to pain radiating along the path of the sciatic nerve, typically from the lower back through the buttock and down the leg. The most common cause is a herniated lumbar disc compressing a nerve root (most often L4, L5, or S1). Other causes include spinal stenosis, piriformis syndrome, and rarely, tumors or injuries along the nerve's course.

Related Structures

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Educational Disclaimer

This content is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider for medical decisions.

Data sources: Terminologia Anatomica, Foundational Model of Anatomy, Wikidata.