Piriformis

The piriformis (Latin: musculus piriformis) is a small, flat and triangular-shaped skeletal muscle located in the gluteal region. It extends between the sacrum, ilium and femur. The piriformis is classified as the lateral rotator and deep gluteal muscle. It lies inferior to the gluteus maximus muscle.

Piriformis
OriginPelvic surface of sacrum, gluteal surface of ilium, sacrotuberous ligament
InsertionGreater trochanter of femur
Action Thigh external rotation, thigh abduction
InnervationNerve to piriformis (L5 - S2)
Blood supply Superior gluteal artery, inferior gluteal artery, internal pudendal artery

Origin

The piriformis originates from the sacrotuberous ligament, pelvic surface of the sacrum and the gluteal surface of the ilium.

Insertion

The piriformis exits the lesser pelvis via the greater sciatic foramen and inserts on the great trochanter of the femur.

Action

The piriformis muscle provides abduction and external (lateral) rotation of the thigh at the hip joint.

Innervation

The piriformis is innervated by the nerve to piriformis (L5 - S2) that arises from the sacral plexus.

Blood supply

The piriformis muscle receives arterial blood supply from the superior and inferior gluteal and internal pudendal arteries. All are branches of the internal iliac artery.