In normal upper-quarter function, the scapula provides a stable base from which glenohumeral mobility occurs.
Stability of the scapula depends on the surrounding musculature. These muscles must dynamically position the glenoid so that efficient glenohumeral movement can occur.
During all movements of the glenohumeral joint especially overhead elevation of the arm, it is of great importance that the scapularstabilizing musculature should be strong enough to properly position the scapula.
The main scapula stabilizers are the Levator Scapulae, Rhomboids major and minor, Serratus anterior, and Trapezii.
These muscle groups function through synergistic co- contraction with rotator cuff to control the scapular movement