Piriformis

Joe Muscolino

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The piriformis is one of the six muscles of the deep lateral rotator group. They are (from superior to inferior):

  • Piriformis
  • Superior gemellus
  • Obturator internus
  • Inferior gemellus
  • Obturator externus (deep to quadratus femoris)
  • Quadratus femoris

ATTACHMENTS:

  • The piriformis attaches from the anterior surface of the sacrum to the superior aspect of the greater trochanter of the femur.

 

ACTIONS:

  • Laterally rotates the thigh at the hip joint (from anatomic position)
  • Abducts the thigh at the hip joint (from anatomic position) (note: this action is relatively weak)
  • Medially rotates the thigh at the hip joint (if the thigh is first flexed approximately 60 degrees or more)
  • Horizontally abducts the thigh at the hip joint (if the thigh is flexed to 90 degrees)
  • Contralaterally rotates the pelvis at the hip joint (reverse closed-chain joint action – from anatomic position)

 

TRIVIA NOTE:

  • The sciatic nerve can be compressed by a tight piriformis, causing symptoms of sciatica. When this occurs, it is called piriformis syndrome.