A bone cutting assembly. The bone cutting assembly includes a guide pin having a distal tip that may be securely inserted into a bone to define a cutting axis and a housing having a cam surface and features which allow the housing to be temporarily secured to the bone. The bone cutting assembly further includes a burr mounting arm which can be fitted on to the guide pin so that it can swing around the cutting axis and also translate up and down the guide pin. The burr mounting arm is configured to act against the cam surface as it is swung around the guide pin, so that the arm is caused to move up or down relative to the guide pin by the action of the cam surface.
