Surgical template with cartilage compensated location

A surgical template system for use on a bone comprises a tool guiding aperture for receiving and guiding a tool to work on the bone; and locating means for locating the tool guiding portion at a predetermined position with respect to the bone such that the guide aperture has a fixed orientation with respect to the bone. The locating means comprises a locating member 31, 310 having a first locating surface, the first locating surface 32 being adapted to conform to either a predetermined surface of cartilage 90 covering an articular 92 surface of the bone or a predicted surface of cartilage covering 91, or assumed to be covering, the predetermined articular surface of the bone; and either interchangeable locating means 320 or an adapter member 33 having a second locating surface 34 and being adapted to attach to the locating member in an operative position in which the second locating surface 34 is adapted to engage the predetermined articular surface of the bone if the cartilage is removed or not present.