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The Piriformis is a member of the Deep Lateral Rotator Group (also known as the Deep 6), composed of the following six muscles (from superior to inferior):
- Piriformis
- Superior gemellus
- Obturator internus
- Inferior gemellus
- Obturator externus
- Quadratus femoris
ATTACHMENTS:
- The piriformis attaches from the sacrum to the greater trochanter of the femur.
- The proximal/medial attachment is onto the anterior surface of the sacrum.
ACTIONS:
- Laterally rotates the thigh at the hip joint.
- Medially rotates the thigh at the hip joint (if the thigh is first flexed approximately 60 degrees or more).
- Abducts the thigh at the hip joint.
- Horizontally abducts the thigh at the hip joint.
- Contralaterally rotates the pelvis at the hip joint.
NOTE: A tight piriformis can compress the sciatic nerve causing symptoms of sciatica. When this occurs, it is called piriformis syndrome.
