Identify the origin, insertion, and primary action of the infraspinatus.

Identify the origin, insertion, and primary action of the infraspinatus.

• A. Origin: supraspinous fossa of the scapula. Insertion: greater tubercle of the humerus. Action: abduction of the arm.
• B. Origin: infraspinous fossa of the scapula. Insertion: greater tubercle of the humerus. Action: external rotation of the humerus.
• C. Origin: subscapular fossa of the scapula. Insertion: lesser tubercle of the humerus. Action: internal rotation.
• D. Origin: infraspinous fossa of the scapula. Insertion: lesser tubercle of the humerus. Action: adduction of the arm.

Answer: (B)