The GH joint is designed primarily degrees in extension. Total ROM in abduction is 90 to 120 degrees, accompanied by approxi- mately 40 degrees of external rotation. The total range of motion of rotation is dependent on the position of the humerus in the frontal plane, with the total ROM increasing to 120 degrees with the arm in 90 degrees abduction compared to 60 degrees with the arm in the neutral position. During elevation of the shoulder, inferior gliding of the humeral head is needed to prevent supe- rior translation of the humeral head as a result of the superior roll that occurs during this motion and to maintain the head of the humerus in its and external rotation.