The annular ligament is a fibrous band that encircles the head of the radius, one of the two bones in the forearm. It helps to stabilize the radius at the elbow joint, allowing for smooth rotation during movements like turning the palm up or down. This ligament plays a crucial role in maintaining the proper alignment of the bones during these actions. In addition to its stabilizing function, the annular ligament also protects the elbow joint from excessive movement that could lead to injuries. It is an essential component of the musculoskeletal system, contributing to the overall functionality and strength of the arm.