The infraspinatus muscle laterally rotates and depresses the head of the humerus.  The infraspinatus and teres minor muscles are the primary lateral rotator muscles that depresss the head of the humerus, with some assistance from the supraspinatus.

Actions

• Laterally rotates the shoulder (glenohumeral joint)
• Adducts the shoulder (g/hjoint)
• Extends the shoulder (g/h joint)
• Horizontally abducts the shoulder (g/h joint)
• Stabilizes the head of the humerus in the glenoid cavity

Origin

• Infraspinous fossa of the scapula

Insertion

• Greater tubercle of the humerus

Nerve Innervation

• Suprascapular from the brachial plexus