What happens when the scapula rotates inadequately?

The shoulder blade (scapula) needs to rotate outward about 60 degrees when the arm is in an overhead position. I often see scapulae with only 30 to 40 degrees of rotation. Inadequate rotation means the arm is not supported properly when moving into overhead positions and can lead to shoulder strain. When the scapula stops rotating, the arm bone must continue the movement against the fixed scapula, creating excessive motion at the shoulder joint. Excessive motion at any joint typically causes pain.