Posterior Muscles of the Shoulder Joint
The following muscles are found on the posterior aspect of the shoulder joint.
Infraspinatus: The infraspinatus muscle (figure 3.33) gets its name from the anatomical structure where it originates: the infraspinous fossa beneath the inferior surface of the spine of the scapula. The infraspinatus muscle inserts on the middle facet of the greater tuberosity of the humerus. Contraction of the infraspinatus muscle produces external rotation and extension of the shoulder joint. The infraspinatus muscle is also part of the rotator cuff.
Place your partner’s shoulder joint in abduction, external rotation, and extension and then locate the infraspinatus muscle (figure 3.34).