Posterior Dislocation of the Shoulder

1

Humeral head (red arrow) lies posterior to the glenoid fossa of the humerus (yellow arrow)

Humeral head (red arrow) lies beneath the acromion process of the scapula (green arrow) and posterior to glenoid (yellow oval)

Humeral head (red arrow) assumes the shape of a “lightbulb” because it is fixed in internal rotation