A tibial component for a knee prosthesis comprises a tibial platform and a wedge-shaped keel which is disengageably attachable to the tibial platform. The tibial platform has a superior surface for supporting a fixed or mobile bearing component and an inferior surface which, when the tibial platform and the keel are engaged with each other, is spaced from an upper surface of the keel. A knee prosthesis having the tibial component , and a system are also provided.