Which rotator cuff muscle performs the initial action of humeral abduction?

The rotator cuff muscle that performs the initial action of humeral abduction is the supraspinatus. This muscle is located at the top of the shoulder and plays a crucial role in the early phase of this movement. During abduction, the supraspinatus is responsible for initiating the first 15 degrees of humeral movement away from the body.

The importance of the supraspinatus lies in its anatomical position and its function; it is positioned above the shoulder joint and has a mechanical advantage that allows it to effectively lift the arm. After the initial movement created by the supraspinatus, other muscles, particularly the deltoid, take over to continue the abduction of the arm.

The infraspinatus and teres major, while contributing to shoulder stability and movements such as external rotation and adduction respectively, do not primarily initiate abduction. The subscapularis is more involved in internal rotation of the humerus. Thus, the unique contribution of the supraspinatus to initiating humeral abduction is why it is recognized as the correct answer in this context.