external rotation a movement at a joint that causes rotation of a limb or part of a limb around its long axis away from the midline of the body, e.g. external rotation at the elbow turns the forearm outwards, bringing the palm of the hand to face forwards, or the whole arm can be externally rotated at the shoulder; the whole leg can be externally rotated from the hip but the knee does not allow external rotation of the lower leg alone. Opposite of internal rotation.