A spacer for a knee replacement prosthesis may be provided. The spacer may include a lower surface, the lower surface having a locking component adapted to interlock with a tibial tray； an upper surface, the upper surface having an optional central femoral guide and a pair of condyle support platforms, each of the condyle support platforms being disposed on an opposite side of the central femoral guide, each of the condyle support platforms being smooth, the surface of each of the condyle support platforms further having a shallow concavity； and a body incorporating the upper and lower surfaces, the body having a hollow outer portion surrounding an internal reservoir, the body being impermeable to fluid； the body further having one or more ports, each with a channel, each channel extending through the hollow outer portion of the body directing the flow of fluid in and out of the port(s).
