Leg · Nerve
Sciatic Nerve
The sciatic nerve is the longest and widest nerve in the body, running from the lower back down each leg. When it is irritated it causes "sciatica" — pain shooting down the leg.
What it is
The sciatic nerve is a large nerve formed from lower spinal nerves, running from the lower back through the buttock and down the back of the leg.
Where it runs
From the lower spine, through the buttock, down the back of the thigh, dividing behind the knee to supply the lower leg and foot.
What it does
Carries movement signals to the muscles of the back of the thigh, the lower leg and foot, and sensation from much of the leg and foot.
When things go wrong
Common problems affecting the sciatic nerve
- Sciatica (irritation causing leg pain, often from a slipped disc)
- Nerve compression
- Injury during hip surgery or injections
Education and reference only. This explains the anatomy in plain terms and is not a diagnosis. New weakness or numbness, facial drooping, or loss of bladder or bowel control can be an emergency — call 999.
Did you know?
An interesting fact
The sciatic nerve is about as wide as a person's thumb — the largest nerve in the body.
Answers
Sciatic Nerve: frequently asked questions
What is sciatica?
Sciatica is pain that travels from the lower back or buttock down the leg, caused by irritation or pressure on the sciatic nerve — often from a slipped disc. Most cases improve with time and staying active.
When should sciatica be checked urgently?
Seek emergency care (999/A&E) if you have numbness around the buttocks/genitals, or new problems controlling your bladder or bowel, as these can signal a serious nerve emergency (cauda equina syndrome).
Related nerves
Explore leg nerves
Sources
Where this is drawn from
- NHS — Nervous system
- Gray's Anatomy for Students
- TeachMeAnatomy — nervous system
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