A device for registering in a medical navigation system a position and/or orientation of a patient's pelvis includes a pelvic registration frame. A plurality of positioning elements are arranged on the pelvic registration frame so as to define a plane, wherein the plurality of positioning elements are movable with respect to each other to enable placement of the positioning elements at defined pelvic points of the patient's pelvis. At least one position transmitter is arranged in an unambiguously defined position and/or orientation relative to the frame.