Abstract: The object of providing a device which renders it possible to allow an artificial knee joint at least temporarily a further degree of freedom so as to enable a natural course of movement is solved by the locking device according to the invention for use in a prosthesis, which consists of an inner ring element comprising at least one depression for receiving a locking element, wherein the inner ring element is mounted in an outer ring element comprising at least one recess for receiving the locking element, and wherein the locking element is retained in the recess such that it projects into the depression and hence prevents twisting of the inner ring element relative to the outer ring element.