A man cannot do abduction and internal rotation of arm. Which of the following muscle is responsible for the both movements:-: (A) Pectoralis major, (B) Subscapularis, (C) Deltoid, (D) Teres major
Answer is C. Deltoid muscle is responsible for the both abduction at the shoulder joint and internal rotation of arm. Deltoid muscle fibres Movements Middle (lateral) fibres abductor at shoulder joint Anterior fibres flexion and medial rotation Posterior fibres extension & lateral rotation Pectoralis major work for adduction (not abduction). Subscapularis and teres major muscles are not involved in abduction, though both of them carry out medial rotation.