Following statement regarding dislocation of the shoulder are true except :

Anterior dislocation is more common in which head of humerus dislocates forward from the glenoid cavity. Anterior dislocation is produced by forced abduction, external rotation and extension of the arm. The features of posterior dislocation of the shoulder are not very striking, and for that reason the injury is often overlooked. An important sign is fixed medial rotation of the arm, which cannot be rotated outwards even as far as the neutral position. There is also flattening anteriorly below the front of the acromion, where the head of the humerus normally forms a rounded bulge.