Pump-handle is a movement of the ribs that results in a change in the anteroposterior diameter of the thorax.[1]
One of the most important functions of the ribs and diaphragm is the change in volume of the thorax that helps inspiration and expiration.[2] In general, the ribs move around two axes.[1] The anterior end of the rib is lower than the posterior end; therefore, during elevation of the rib, the anterior end also moves forwards. Movement at costovertebral joints 2 to 6 about a side-to-side axis results in raising and lowering the sternal end of the rib, the "pump-handle" movement. This occurs mostly in the vertebrosternal ribs. In elevation, this increases the anteroposterior diameter of the thorax.[1][3]