Sciatic nerve

Dr Jeremy Jones et al.

The sciatic nerve arises from the sacral plexus from the roots of L4-S3 and runs through the buttock and down the lower limb. It is the longest and widest single nerve in the body.

Origin

The nerve forms from the anterior division of the L4-S3 roots (which forms the tibial component) and posterior divisions of the L4-S2 roots (which forms the common peroneal component) of the sacral plexus.

Course

The sciatic nerve enters the lower limb by exiting the pelvis through the greater sciatic foramen, below the piriformis muscle and above the superior gemellus muscle.

It descends midway in between the greater trochanter of the femur and the tuberosity of the ischium and in the posterior compartment of the thigh to about its lower third, where it divides into two large terminal branches:

Relations
  • anteriorly
    • upper part: posterior surface of the ischium, nerve to quadratus femoris, obturator internus, the gemelli
    • lower part: adductor magnus
  • posteriorly
    • upper part: gluteus maximus
    • lower part: long head of biceps femoris (crosses obliquely)

In the upper part of its course, it is accompanied by the posterior femoral cutaneous nerve and the inferior gluteal artery, and is covered by the gluteus maximus muscle.

The nerve gives off articular and muscular branches before dividing into two terminal branches - the tibial nerve and the common peroneal nerve.

Articular branches

The articular branches arise from the upper part of the nerve and supply the hip joint, perforating the posterior part of its capsule; they are sometimes derived from the sacral plexus.

Muscular branches

The sciatic nerve supplies the following muscles:

The division of the sciatic nerve into the common peroneal and tibial nerves may take place at any point between the sacral plexus and the lower third of the thigh. When it occurs at the sacral plexus, the common peroneal nerve usually pierces the piriformis muscle.

Ultrasound
  • appears as a round hypoechoic round structure, situated deep to piriformis and gluteus maximus muscles 3

Pain and functional symptoms may be caused by a compression or irritation of the sciatic nerve. This may be caused by:


Lower limb anatomy
Abdominal and pelvic anatomy
Share article

Article Information

rID: 5003
Section: Anatomy
Synonyms or Alternate Spellings:
  • Sciatic nerves

Support Radiopaedia and see fewer ads

Cases and Figures

  • Drag
    Figure 1: sciatic nerve
    Drag here to reorder.
  • Drag
    Figure 2: sacral plexus
    Drag here to reorder.
  • Drag
    Figure 3: sciatic nerve
    Drag here to reorder.
  • Drag
    Figure 4: relations in the gluteal region
    Drag here to reorder.
  • Drag
    Figure 5: with a traumatic sciatic nerve injury
    Drag here to reorder.
  • Updating… Please wait.
    Loadinganimation

    Alert accept

    Error Unable to process the form. Check for errors and try again.

    Alert accept Thank you for updating your details.