Which muscle is primarily responsible for lateral rotation of the shoulder?

• A. Teres major
• B. Teres minor
• C. Infraspinatus
• D. All of the above

Answer: (D)

The primary muscle responsible for lateral rotation of the shoulder is the infraspinatus. This muscle, part of the rotator cuff group, plays a key role in providing stability to the shoulder joint while also facilitating lateral rotation of the humerus. The teres minor also assists in this movement, but it is primarily the infraspinatus that is noted for this specific action.

Teres major, however, is primarily responsible for medial rotation and adduction of the shoulder, not lateral rotation, which makes it less relevant to this specific action. Therefore, while both the infraspinatus and teres minor contribute to lateral rotation, the teres major does not, highlighting that not all listed muscles work towards this specific movement. The answer indicating all of the above would be misleading, as it implies that teres major is equally involved in lateral rotation, which is not the case.