A system for replacement of a knee joint of a patient, the system comprising: a tibial baseplate configured to couple to a resected proximal surface of a tibia; one or more bearings (504, 604, 704); and an insert disposable between the one or more bearings and the tibial baseplate, the insert comprising: a proximal surface configured to interface with the one or more bearings; a post (510, 618) extending from the proximal surface; and a distal surface spaced from the proximal surface and configured to interface with the tibial baseplate, wherein the distal surface is configured with a connection mechanism to connect with the tibial baseplate, characterised in that the one or more bearings comprises a plurality of bearings, each of the plurality of bearings having a different construction and being configured to simulate a bearing from a different knee system, wherein each of the plurality of bearings is configured to articulate with a femoral implant of a different construction, wherein the post is configured to be received in a recess in each of the plurality of bearings, and wherein each of the plurality of bearings is configured to pivot about the post to move relative to the proximal surface. a tibial baseplate configured to couple to a resected proximal surface of a tibia; one or more bearings (504, 604, 704); and an insert disposable between the one or more bearings and the tibial baseplate, the insert comprising: a proximal surface configured to interface with the one or more bearings; a post (510, 618) extending from the proximal surface; and a distal surface spaced from the proximal surface and configured to interface with the tibial baseplate, wherein the distal surface is configured with a connection mechanism to connect with the tibial baseplate, characterised in that the one or more bearings comprises a plurality of bearings, each of the plurality of bearings having a different construction and being configured to simulate a bearing from a different knee system, wherein each of the plurality of bearings is configured to articulate with a femoral implant of a different construction, wherein the post is configured to be received in a recess in each of the plurality of bearings, and wherein each of the plurality of bearings is configured to pivot about the post to move relative to the proximal surface. a proximal surface configured to interface with the one or more bearings; a post (510, 618) extending from the proximal surface; and a distal surface spaced from the proximal surface and configured to interface with the tibial baseplate, wherein the distal surface is configured with a connection mechanism to connect with the tibial baseplate, characterised in that the one or more bearings comprises a plurality of bearings, each of the plurality of bearings having a different construction and being configured to simulate a bearing from a different knee system, wherein each of the plurality of bearings is configured to articulate with a femoral implant of a different construction, wherein the post is configured to be received in a recess in each of the plurality of bearings, and wherein each of the plurality of bearings is configured to pivot about the post to move relative to the proximal surface.