Where does the infraspinatus muscle insert?

• A. Greater tubercle of the humerus
• B. Lesser tubercle of the humerus
• C. Intertubercular groove
• D. Deltoid tuberosity

Answer: (A)

Understanding where the rotator cuff muscles attach helps explain shoulder stability and movement. The infraspinatus tendon attaches to the greater tubercle of the humerus, specifically the middle facet, which positions it to externally rotate the arm and help keep the humeral head centered in the glenoid during movement. The greater tubercle is the common insertion site for these tendons, with the supraspinatus attaching to the superior facet and teres minor to the inferior facet. The lesser tubercle is where the subscapularis inserts, the intertubercular groove houses the long head of the biceps tendon, and the deltoid tuberosity is where the deltoid inserts.