Tibial trial insert system , comprising: - a bearing component having a superior articulating surface and an inferior surface ; - a plate component having a superior surface and an inferior fixation surface ; - at least a first spacing adjustment assembly and a second spacing adjustment assembly , - each spacing adjustment assembly configured to be arrangeable between the inferior surface of the bearing component and the superior surface of the plate component , and - each spacing adjustment assembly having at least one superior connector element configured to removably engage with the bearing component and at least one inferior base element configured to removably engage with the plate component , thereby allowing to exchange the first spacing adjustment assembly against and the second spacing adjustment assembly and vice versa, wherein the connector element is movably coupled to the base element in proximal/distal direction; - a plurality of shims , each shim configured to be slidable between an inferior surface of the connector element and a superior surface of the base element of the first spacing adjustment assembly and/or the second spacing adjustment assembly to adjust a proximal/distal height of the respective spacing adjustment assembly , in order to thereby adjust a relative proximal/distal spacing between the bearing component and the plate component ; - wherein the first spacing adjustment assembly is configured to allow an adjustment of the proximal/distal spacing within a first adjustment range and the second spacing adjustment assembly is configured to allow an adjustment of the proximal/distal spacing within a second adjustment range. - a bearing component having a superior articulating surface and an inferior surface ; - a plate component having a superior surface and an inferior fixation surface ; - at least a first spacing adjustment assembly and a second spacing adjustment assembly , - each spacing adjustment assembly configured to be arrangeable between the inferior surface of the bearing component and the superior surface of the plate component , and - each spacing adjustment assembly having at least one superior connector element configured to removably engage with the bearing component and at least one inferior base element configured to removably engage with the plate component , thereby allowing to exchange the first spacing adjustment assembly against and the second spacing adjustment assembly and vice versa, wherein the connector element is movably coupled to the base element in proximal/distal direction; - a plurality of shims , each shim configured to be slidable between an inferior surface of the connector element and a superior surface of the base element of the first spacing adjustment assembly and/or the second spacing adjustment assembly to adjust a proximal/distal height of the respective spacing adjustment assembly , in order to thereby adjust a relative proximal/distal spacing between the bearing component and the plate component ; - wherein the first spacing adjustment assembly is configured to allow an adjustment of the proximal/distal spacing within a first adjustment range and the second spacing adjustment assembly is configured to allow an adjustment of the proximal/distal spacing within a second adjustment range. <EOS>