An acetabular cup (16) is provided with improved means for giving at least temporary mechanical anchoring in position of cup (16) in an acetabular socket. The cup (16) comprises a plurality of anchors (19) mounted to the sidewall (18) of the cup. Each anchor is moveable between a retracted position and an outwardly projecting position, in which the anchor is engageable with the wall of the acetabular socket in order to locate the cup in the socket. Each anchor takes the form of a blade (19).
