Which shoulder muscle is primarily responsible for abducting the arm?

The supraspinatus muscle is primarily responsible for abducting the arm, particularly during the initial phase of arm elevation. It is one of the four rotator cuff muscles and is located at the top of the shoulder. When the arm is raised, the supraspinatus initiates the abduction movement, allowing the arm to lift away from the body. This muscle plays a crucial role in stabilizing the shoulder joint while also facilitating movement.

In contrast, the subscapularis primarily functions in internal rotation of the arm, while the infraspinatus is primarily responsible for external rotation and stabilization of the shoulder. The levator scapulae primarily acts to elevate the scapula and is not a primary mover for arm abduction. Understanding the specific roles of these muscles can help clarify their contributions to shoulder movements.