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

The infraspinatus muscle is primarily responsible for the lateral rotation of the humerus. This muscle is one of the rotator cuff muscles and is located on the posterior aspect of the scapula. It plays a crucial role in stabilizing the shoulder joint and enabling various arm movements, particularly those that require external rotation of the arm.

During lateral rotation, the infraspinatus acts as a powerful external rotator, helping to turn the humeral head outward away from the body. This movement is vital in numerous activities, such as throwing a ball or reaching behind the back.

In contrast, the teres major, although involved in shoulder movements, primarily assists with medial rotation and adduction. The latissimus dorsi is more known for its functions in shoulder extension and adduction while also medially rotating the arm. The subscapularis is primarily responsible for medial rotation of the humerus. Understanding the specific actions of these muscles underlines the importance of the infraspinatus in facilitating lateral rotation effectively.