Original Editor - Wendy Walker
A thick, triangular muscle; one of the 4 muscles which comprise the Rotator Cuff of the shoulder.
The posterior aspect of greater tuberosity of humerus, and the capsule of shoulder joint.
Suprascapular Nerve (C5 & C6)
Suprascapular and circumflex scapular arteries.
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. 
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.
Recent Related Research (from Pubmed)
- 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)