Nerve
Sciatic nerve
Large sacral-plexus nerve containing tibial and fibular divisions
High-yield
The usual nerve passes below piriformis, but both this relationship and its division level vary. The two components can separate high in the pelvis or buttock rather than only just above the knee.
Overview
The sciatic nerve carries two major divisions together through the buttock and posterior thigh. These supply the hamstring region and continue as the tibial and common fibular nerves, which provide the main motor routes to the leg and foot.
Reference facts
- Root value
- L4–S3 ventral rami contributing through the sacral plexus
- Course
- Usually leaves the greater sciatic foramen below piriformis, travels deep to gluteus maximus and the long head of biceps femoris, then separates into tibial and common fibular nerves at a variable level
- Motor
- Tibial division to most hamstrings and the hamstring part of adductor magnus; fibular division to short-head biceps femoris; terminal nerves to the leg and foot muscles
- Sensory
- Through its branches, most leg and foot skin apart from the medial saphenous territory; no usual direct cutaneous supply to thigh skin
Clinical correlation
A posterior hip dislocation can stretch or compress the sciatic nerve, causing weakness or sensory changes farther down the limb. The severity and distribution depend on which fibers are injured; sciatic injury is not present in every dislocation.
Frequently asked questions
What are the roots of the sciatic nerve?
The sciatic nerve arises from L4–S3 ventral rami contributing through the sacral plexus.
What muscles does the sciatic nerve supply?
Tibial division to most hamstrings and the hamstring part of adductor magnus; fibular division to short-head biceps femoris; terminal nerves to the leg and foot muscles.
What is the sensory distribution of the sciatic nerve?
Through its branches, most leg and foot skin apart from the medial saphenous territory; no usual direct cutaneous supply to thigh skin.
What is the course of the sciatic nerve?
Usually leaves the greater sciatic foramen below piriformis, travels deep to gluteus maximus and the long head of biceps femoris, then separates into tibial and common fibular nerves at a variable level.