The sternoclavicular (SC) joint is the pivot on which the shoulder girdle moves on the trunk. Dislocation of this joint most often results from a fall onto the shoulder.

This joint is a diarthrodial joint, permitting rotary movement of the clavicle. Internal rotation of the arm is associated with the maximum degree of rotation of the clavicle so that the bone protrudes anteriorly.

A sharp, forward thrust of the shoulder girdle, as in the motion of throwing, depends on the integrity of this joint....