The piriformis is a pear-shaped muscle deep in the buttock. It arises from the anterior surface of the sacrum and inserts on the upper border of the greater trochanter. The nerve to piriformis (S1-S2) supplies it, and it laterally rotates the extended hip. It is the key landmark of the gluteal region.
| Origin | Anterior surface of the sacrum (S2-S4) and the margin of the greater sciatic notch. |
|---|---|
| Insertion | Superior border of the greater trochanter of the femur. |
| Innervation | Nerve to piriformis (L5-S2). |
| Blood supply | Superior and inferior gluteal arteries. |
| Action | Laterally rotates the extended hip and abducts the flexed hip. |
3D model: BodyParts3D (CC BY 4.0), adult male reference anatomy. Highlighted structure shown with nearby bones for context.
The piriformis leaves the pelvis through the greater sciatic foramen and divides it into a suprapiriform and an infrapiriform part. The sciatic nerve usually leaves below the muscle.
It is the landmark that organises the vessels and nerves leaving the pelvis through the greater sciatic foramen.
It laterally rotates the extended hip.
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