An apparatus for identifying, during total knee replacement surgery, a position of a center of a femoral head of a patient within a plane parallel to a frontal plane, comprises a marking plate placed to cover, in a direction perpendicular to the frontal plane, a site where the femoral head center of the patients body is located a pivotal arm having a pivotal shaft arranged to extend in a direction perpendicular to the frontal plane and a marker attached to the pivotal arm, for depicting a circular arc on the marking plate according to rotation of the pivotal arm the pivotal shaft being placed at a distal end of a femur of the patient, a distance from the pivotal shaft to the marker in a direction parallel to the frontal plane being equal to a preliminarily measured distance from the distal end of the femur to the femoral head center.
