[Stress to the lateral ankle joint ligament complex in confined imaging with an a.-p. radiation path]

Physical definition and laws of rotating systems will be stated. The application for supination in ankle joint shows, that lever action increases the force applied up to four times in case of stress X-rays in the a.-p. view. As quoted in literature, the test power of up to 25 kp means a loading of the lateral collaterals up to 100 kp. An additional iatrogenic rupture of already traumatically partially sprained structures seems possible. The critical judgement of five different methods producing stress X-rays of the ankle joint shows the weak points of this test system. Beck's method seems sufficient for precise statements and judgement of the stress X-ray tests without endangering ligaments so far unsprained.