Which structure encircles the glenoid fossa and increases its depth for stability?

• A. Articular cartilage
• B. Glenoid labrum
• C. Joint capsule
• D. Synovial membrane

Answer: (B)

The glenoid labrum is the structure that encircles the rim of the glenoid fossa, deepening the socket to improve stability. This fibrocartilaginous rim increases the congruency between the glenoid and the humeral head, which helps resist dislocation and enhances joint stability during various shoulder movements. It also provides an attachment site for the joint capsule and glenohumeral ligaments, integrating soft-tissue support with the bony socket. Articular cartilage covers the joint surfaces but doesn’t encircle the rim; the joint capsule encases the joint as a whole, and the synovial membrane lines the capsule to produce fluid—neither of these deepens the glenoid.