- Anatomy:
    - origin: anterior surface of sacrum between and lateral to anterior sacral foramen, capsule of sacroiliac articulation, margin of the greater sciatic foramen,
          and sacrotuberous ligament;
    - insertion: superior border of greater trochanter of femur;
    - action: external rotation of hip & abducts thigh at the hip;
    - nerve supply: sacral plexus, L5, S1, S2;
    - synergists: superior and inferior gemellus, quadratus femoris, internal obturator and external obturator

Piriformis syndrome.

Piriformis Syndrome: Anatomic Considerations, a New Injection Technique, and a Review of the Literature

Piriformis and obturator internus morphology: a cadaveric study.