During elbow flexion, which axis does the forearm move around?

During elbow flexion, the forearm moves around the X axis. This movement occurs at the humeroulnar joint where the motion is primarily one of bending. The X axis, in this context, is oriented horizontally from side to side, allowing for the flexion and extension movements of the elbow. As the forearm moves upwards towards the shoulder while flexing, it rotates around this axis, causing an angle between the forearm and the upper arm to decrease. Understanding this concept is essential for analyzing joint mechanics and how different axes of rotation affect movement patterns in activities of daily living and various sports.