Which muscle flexes, adducts, and medially rotates the shoulder?

Which muscle flexes, adducts, and medially rotates the shoulder?

• A. Pectoralis Major
• B. Latissimus Dorsi
• C. Deltoid
• D. Infraspinatus

Answer: (A)

The muscle that can bring the arm forward, toward the body, while also pulling it in and rotating it inward is the pectoralis major. Its clavicular part primarily flexes the shoulder (lifting the arm forward), while the sternocostal part helps with adduction and medial (inward) rotation of the humerus. This combination matches the actions described. Other muscles don’t line up with all three actions together. Latissimus dorsi, for example, is a strong adductor and medial rotator but mainly extends the shoulder rather than flexing it. The deltoid can flex the shoulder via its anterior fibers, but it’s best known for abduction with the middle fibers and doesn’t provide the same coordinated trio of flexion, adduction, and medial rotation. Infraspinatus primarily laterally rotates the shoulder and stabilizes the joint, not flexion or medial rotation.

The muscle that can bring the arm forward, toward the body, while also pulling it in and rotating it inward is the pectoralis major. Its clavicular part primarily flexes the shoulder (lifting the arm forward), while the sternocostal part helps with adduction and medial (inward) rotation of the humerus. This combination matches the actions described.

Other muscles don’t line up with all three actions together. Latissimus dorsi, for example, is a strong adductor and medial rotator but mainly extends the shoulder rather than flexing it. The deltoid can flex the shoulder via its anterior fibers, but it’s best known for abduction with the middle fibers and doesn’t provide the same coordinated trio of flexion, adduction, and medial rotation. Infraspinatus primarily laterally rotates the shoulder and stabilizes the joint, not flexion or medial rotation.