Piriformis Muscle Anatomy

Piriformis Muscle

Origin: Attaches to the pelvic surface of the sacrum between the anterior sacral foramina, the margin of the greater sciatic foramen, and the sacrotuberous ligament
Insertion: Attaches to the superior margin of the greater trochanter of the femur
Actions: Assists with external rotation and abduction of the thigh
Innervation: Nerve to piriformis (S1, S2)
Blood Supply: Inferior gluteal artery from the internal iliac artery

Primary Actions of the Piriformis Muscle

The piriformis does not perform a primary action, it assists other muscles with movement of the thigh and hip stabilization.

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Secondary Actions of the Piriformis

1. Assists with external rotation of the thigh at the hip
Agonists:

  • Obturator internus
  • Obturator externus
  • Gemellus superior
  • Gemellus inferior
  • Quadratus femoris

Antagonists:

  • Tensor Fasciae Latae
  • Gluteus Minimus (anterior fibers)
  • Gluteus Medius (anterior fibers)

Gluteus maximus and sartorius also assist with external rotation of thigh at the hip when the hip is extended.


2. Assists with the abduction of the thigh at the hip when the hip is flexed

  Agonists:

  • Gluteus Maximus (upper fibers)
  • Gluteus Medius
  • Gluteus Minimus

  Antagonists:

  • Adductor Longus
  • Adductor Brevis,
  • Adductor Magnus