Tibial prosthesis systems for implantation or use in a knee joint are disclosed. A tibial prosthesis system can include a bearing component, a base component, a shim component, and optionally a spacer component. The shim or spacer component can be inserted between an inferior surface of the bearing component and a superior surface of the base component. The insertion of the shim or spacer component can provide spacing adjustment between the bearing and base components. The shim component can include one or both of a medial edge having a different height than a lateral edge or an anterior edge having a different height than a posterior edge. The differing edge height of the shim component can provide a surgeon with knee joint kinematic insight regarding an angled bone cut before the cut is made, and can allow for sizing of an appropriately permanent prosthesis system using a reduced number of provisional components.