The use of an orthopedic aid with two parts (15, 16) which are movable relative to one another and with a locking device for locking the two parts (15, 16) in a predetermined relative position and for unlocking the parts (15, 16) in order to permit movement of the parts (15, 16) with respect to one another is made much safer by virtue of the fact that at least one signaling arrangement (36, 40, 41, 42) is provided which emits a particular signal for the locking state or upon unlocking of the locking device. The risk of accidents due to the parts (15, 16) being incorrectly locked is at least substantially reduced.
