The elbow joint is a hinge joint formed by the junction of the humerus and the radius and ulna bones of the lower arm. Strong ligaments hold the joint together in addition to the muscles and tendons. There is also movement between the radius and ulna bones, which allows for pronation and supination of the forearm.
In flexion the forearm moves toward the upper arm or vice versa. In extension the forearm moves away from the upper arm in an arm-straightening action. The reverse action, in which the upper arm moves away from the forearm, is also possible. This is seen in the lowering phase of a pull-up or chinup.
