Original Editor - Wendy Walker
Description[edit | edit source]
A thick, triangular muscle; one of the 4 muscles which comprise the Rotator Cuff of the shoulder.
Origin[edit | edit source]
Insertion[edit | edit source]
The posterior aspect of greater tuberosity of humerus, and the capsule of shoulder joint.
Nerve Supply[edit | edit source]
Suprascapular Nerve (C5 & C6)
Blood Supply[edit | edit source]
Suprascapular and circumflex scapular arteries.
Action[edit | edit source]
Infraspinatus is the main external rotator of the shoulder joint.
It assists in producing shoulder extension.
With the arm fixed, it abducts the inferior angle of the scapula. 
Function[edit | edit source]
It provides the primary muscle force for external rotation of the shoulder.
Along with the rest of the Rotator Cuff muscles it provides stability to the shoulder complex.
Clinical Relevance[edit | edit source]
Atrophy in the supraspinatus and infrapinatus muscles, usually indicates compression on the suprascapular never near the scapular notch, such compression can be seen in overhead athletes and SLAP lesions. While isolated weakness or atrophy in the infrapinatus muscle can be seen in suprascapular nerve compression in the spinoglenoid notch, compression of the nerve in the spinpglenoid notch is usually due to a ganglion cyst.
A study by Simons et al, described that infraspinatus muscle trigger points are associated with referred pain to the middle and anterior deltoid regions. Myofascial release techniques at the infraspinatus muscle may help shoulder pain.
Assessment[edit | edit source]
To evaluate the infraspinatus muscle the arm is placed in neutral abduction or adduction position with the elbow flexed 90 degrees. Lateral rotation of the shoulder is done against resistance, the test is positive if there is pain or weakness. 
Resources[edit | edit source]
[edit | edit source]
- Gray H. Anatomy of the Human Body. Philadelphia: Lea & Febiger, 1918. Available from https://www.bartleby.com/107/123.html (accessed on 29/2/2016)
- Wheeles CR. Infraspinatus. Available from: http://www.wheelessonline.com/ortho/infraspinatus (last accessed 29/2/2016)
- AnatomyExpert. 3D Infraspinatus- infraspinatus. Available from: http://www.anatomyexpert.com/app/structure/5510/554/ (last accessed on 29/2/2016)
- Williams JM, Sinkler MA, Obremskey W. Anatomy, shoulder and upper limb, infraspinatus muscle. StatPearls [Internet]. 2020 May 24.
- Moccia D, Nackashi AA, Schilling R, Ward PJ. Fascial bundles of the infraspinatus fascia: anatomy, function, and clinical considerations. Journal of anatomy. 2016 Jan;228(1):176-83.
- Maruvada S, Madrazo-Ibarra A, Varacallo M. Anatomy, rotator cuff.