📚Shoulder abduction isn’t just the arm lifting out to the side, it’s a coordinated effort across multiple joints.

🔎The movement starts at the glenohumeral joint, where the supraspinatus initiates abduction and the deltoid drives it. At the same time, the rotator cuff stabilizes the humeral head to prevent excessive upward movement.

🧠As the arm continues upward, the scapula joins in. This creates the classic 2:1 rhythm, meaning for every 3° of motion, 2° comes from the shoulder joint and 1° from the scapula.

👉This scapular motion is controlled by the trapezius and serratus anterior, helping rotate the scapula upward and clear space for the arm to move overhead.

✅Smooth shoulder motion is less about one muscle and more about how everything works together.