The pivot joint between your radius and ulna allow you to rotate your palm forward or anteriorly in a motion called supination, and turning it backward or posteriorly is called pronation.

桡骨和尺骨之间的枢轴关节允许你在一个叫做旋后的动作中向前或向前旋转手掌，向后或向后旋转叫做内旋。