Which muscle extends the shoulder, medially rotates the arm, and adducts the shoulder?

• A. Teres Major
• B. Deltoid
• C. Supraspinatus
• D. Infraspinatus

Answer: (A)

The movement pattern tested is a combination of extending the shoulder, medially rotating the arm, and adducting the shoulder. Teres major is the muscle that can produce all three of these actions together. Its fibers pull the humerus backward (extension), rotate it toward the midline (medial rotation), and bring the arm toward the body (adduction). Its attachment from the inferior angle of the scapula to the medial lip of the intertubercular groove gives a line of pull that achieves this blend of movements, fitting the described action set.

The other muscles don’t combine these three actions in the same way. The deltoid mainly elevates the arm (abduction) and, depending on the fibers, can flex or extend with different rotations but doesn’t produce true medially oriented adduction. Supraspinatus initiates abduction and stabilizes the joint, not extension or medial rotation. Infraspinatus primarily laterally rotates the arm and does not extend or adduct.