Which rotator cuff muscle is responsible for internal rotation?

The subscapularis is the rotator cuff muscle primarily responsible for internal rotation of the shoulder. This muscle is located on the anterior (front) surface of the scapula and plays a crucial role in stabilizing the shoulder joint while also allowing for various shoulder movements, particularly internal rotation.

Internal rotation occurs when the arm moves towards the body and the humerus (the bone of the upper arm) rotates inward. The subscapularis, by contracting, pulls the head of the humerus toward the center of the body, facilitating this movement. In contrast, the other muscles mentioned—such as the infraspinatus and teres minor—are primarily involved in external rotation, while the supraspinatus assists with arm abduction. Understanding the specific functions of each rotator cuff muscle is essential for recognizing how they contribute to shoulder mechanics and stability.