An overhead thrower must have tremendous shoulder range of motion to generate acceleration, yet have enough stability in the bony and soft tissues to prevent injury from the high forces associate with pitching. Any disruption in this balance can lead to excess strain on one or more structures in the kinetic chain.
We know that overhead sports torque the humerus. The glenohumeral joint is designed for mobility; and anchored to a relatively stable scapula and torso. In youth baseball pitchers, excessive humeral torque can stress the vulnerable proximal epiphyseal cartilaginous growth plate, leading to a painful condition called Little League Shoulder.