Which muscle is primarily responsible for shoulder lateral rotation?

The infraspinatus muscle is primarily responsible for shoulder lateral rotation. This muscle is located on the back of the shoulder blade and is one of the rotator cuff muscles. When it contracts, it pulls the head of the humerus (the upper arm bone) outward and backward, facilitating lateral rotation of the shoulder joint.

Unlike other muscles listed, the infraspinatus is specifically oriented to perform this action due to its anatomical position and attachment points. The teres major, while important for shoulder movement, primarily functions in medial rotation, adduction, and extension. The supraspinatus assists in shoulder abduction, and the subscapularis is focused on medial rotation of the shoulder. This functional specificity of the infraspinatus highlights its crucial role in the lateral rotation of the shoulder.