Glenoid retroversion contributes to which type of instability?

• A. Anterior Instability
• B. Posterior Instability
• C. Inferior Instability
• D. Superior Instability

Answer: (B)

Glenoid orientation directly governs where the socket is most stable. When the glenoid fossa is retroverted, the socket faces more toward the back, making the humeral head less stable in the posterior direction. Under clinical loads or movements—like abduction with external rotation—the head can translate posteriorly or even dislocate if the posterior structures aren’t able to resist it. So, increased glenoid retroversion predisposes to posterior instability.