Abstract: A device for stabilizing the pelvis of a lying patient in a preselected angular position relative to a conventional flat bed includes a generally, disc shaped body with two basically parallel planar surfaces. The body is intended to be placed between the lower extremities of the patient and is designed with a cavity, which extends from the edge of the body toward its center and conforms to and is somewhat bigger than the contours of the patient's pelvis as seen from the side, and has parts protruding from the respective planar surfaces, and preferably arranged in pairs on opposite sides of the body. The protruding parts are arranged to support the body far enough above the bed to give room for one extremity between the bed and the planar surface facing the bed while the other extremity rests on the opposite planar surface, thereby providing some moving space for the extremities between the protruding parts.