What is the role of the rotator cuff in glenohumeral rhythm?

• A. Prevent migration and impingement
• B. Increase mobility by loosening static stability
• C. Decrease stability
• D. Provide bony stability

Answer: (A)

The rotator cuff acts as a dynamic stabilizer for the shoulder, keeping the humeral head centered in the glenoid as you lift the arm. This centering prevents superior migration of the head that would lead to impingement under the acromion and disrupt smooth glenohumeral rhythm. When the deltoid pulls the humerus upward, the rotator cuff compresses and centers the head, allowing coordinated movement between the glenohumeral joint and the scapula (the scapulohumeral rhythm) without painful impingement.

This is not about loosening static stability to gain more mobility, nor about providing bony stability. The rotator cuff provides dynamic stability that preserves joint congruency and reduces impingement, enabling efficient glenohumeral rhythm.