Which muscles contribute to internal rotation of the shoulder?

Which muscles contribute to internal rotation of the shoulder?

• A. Subscapularis, pectoralis major.
• B. Pectoralis major, latissimus dorsi, and teres major.
• C. Subscapularis, pectoralis major, latissimus dorsi, teres major.
• D. Subscapularis, pectoralis major, latissimus dorsi, teres major, and anterior deltoid.

Answer: (D)

Internal rotation of the shoulder is produced by several muscles that medially rotate the humerus, with subscapularis providing the primary pull from the front of the shoulder. The latissimus dorsi and teres major wrap around and insert on the humerus to generate strong medial rotation, especially when the arm is extended or adducted. Pectoralis major adds a powerful inward twist as well, particularly when the arm is flexed or adducted. The anterior fibers of the deltoid can also contribute to internal rotation when the arm is in flexion, because their pull has a medial component in that position. Because internal rotation involves multiple muscles acting together across different shoulder positions, including all of these muscles gives the most complete and accurate description of contributors.

Internal rotation of the shoulder is produced by several muscles that medially rotate the humerus, with subscapularis providing the primary pull from the front of the shoulder. The latissimus dorsi and teres major wrap around and insert on the humerus to generate strong medial rotation, especially when the arm is extended or adducted. Pectoralis major adds a powerful inward twist as well, particularly when the arm is flexed or adducted. The anterior fibers of the deltoid can also contribute to internal rotation when the arm is in flexion, because their pull has a medial component in that position. Because internal rotation involves multiple muscles acting together across different shoulder positions, including all of these muscles gives the most complete and accurate description of contributors.