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(See also: Rotator cuff)

  • origin: infraspinatus fossa of scapula
  • insertion: posterior aspect of greater tuberosity of humerus, capsule of shoulder joint;
  • demensions: infraspinatus has been shown to average 29 mm wide, with a mean medial-to-lateral width of 19 mm
  • action: extension, horizontal extension and lateral rotation of humerus at the shoulder joint.
    • the infraspinatus is the primary muscle force resposible for external rotation;
    • reversed origin insertion action: with the arm fixed, abducts the inferior angle of the scapula;
    • synergists: Teres Minor, Subscapularis, Deltoid;
  • nerve supply: suprascapular, C5, C6