Usually a history of a direct blow on the front of the shoulder, or forced internal rotation of the abducted arm.
On examination, the shoulder has an abnormal contour, with a bulge posteriorly. Invariably the shoulder is locked in full internal rotation - virtually pathognomonic for this condition.
Radiography shows the characteristic lightbulb sign on AP view; an axillary lateral view is needed to actually view the dislocation.
Last reviewed 01/2018