Shoulder internal rotation (or medial rotation) is a rotary movement at the shoulder (glenohumeral) joint around the longitudinal axis of the humerus (upper arm bone) towards the centre of the body – turning the upper arm inwards – see Figures 1 and 2.
The key muscles involved in this movement are the sternal and clavicular heads of the pectoralis major, the latissimus dorsi, and the anterior deltoid. The teres major and subscapularis also play a weak role, as does the supraspinatus when the shoulder is flexed.
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