The greater tuberosity fragment tends to be displaced superiorly and posteriorly due to the pull of the rotator cuff (supraspinatus and infraspinatus tendon). If the greater tuberosity heals with displacement (5 mm or more), it may impinge upon the coracoacromial arch, limiting motion, and producing pain. In this position, it provides a shorter lever arm for the supra- and infraspinatus tendons, and thus weakens them.
Note that the greater tuberosity fragment tends to redisplace, causing delayed bone healing. The biceps tendon may be incarcerated in the fracture.