What is the role of the annular ligament?

• A. To wrap around the head of the ulna
• B. To stabilize the distal radius during extension
• C. To stabilize the proximal radius to the ulna during pronation and supination
• D. To connect the humerus and scapula

Answer: (C)

The role of the annular ligament is to stabilize the proximal radius to the ulna during pronation and supination. This ligament forms a ring-like structure that encircles the radial head and holds it in place against the ulna, allowing for the necessary movement between these two bones. When the forearm rotates, such as during actions like turning a doorknob or flipping a pancake, the annular ligament ensures that the radius can pivot smoothly without dislocating from its joint. This stabilization is crucial for maintaining proper mechanics and preventing injuries in the elbow and forearm during rotational movements.

In contrast, the other options do not accurately represent the function of the annular ligament. The annular ligament does not wrap around the head of the ulna; rather, it is associated with the radius. It does not play a role in stabilizing the distal radius during extension, nor does it connect the humerus and scapula, which are linked by different ligaments and structures related to shoulder stability.