Anterior shoulder dislocation most commonly results from which mechanism?

• A. Falling on an outstretched hand
• B. Direct blow to the shoulder
• C. Sudden twisting movement
• D. All of the above

Answer: (D)

Anterior dislocation happens when the humeral head is forced out of the glenoid in an anterior direction, typically when the arm is in a vulnerable position—abduction with extension and external rotation. Falling on an outstretched hand is the classic scenario because the impact drives the shoulder through that vulnerable position and transmits force to the joint, pushing the head forward. But a direct blow to the shoulder can also push the head anteriorly if the arm is in or moved into a position that favors forward displacement, and a sudden twisting movement can do the same by rapidly changing the forces across the joint. Since all these situations can end with the humeral head popping out anteriorly, all of the above is the best answer.