An expandable mold configured to be arthroscopically introduced into a joint for in-situ formation of a joint replacement prosthesis, and a flowable, curable substance configured for forming the joint replacement prosthesis inside said mold. In addition, a surgical kit for arthroscopic, in-situ formation of a joint replacement prosthesis, the surgical kit comprising: an expandable prosthesis mold configured to be arthroscopically introduced into a joint； at least one arthroscopic instrument configured to form an ellipsoidal cavity between two interfacing bones of the joint, for receiving said mold； and a first flowable, curable substance configured for forming the prosthesis inside said mold.
