Instrumentation for guiding a surgeon in performing a unicompartmental knee replacement includes a tibial block having a guide, and a milling tool adapted to engage the guide, such that the surgeon can mill the desired tibial bone bed by directing the milling tool along the guide. Further including a femoral jig having a cutting slot, a guide, and a milling tool adapted to engage the guide, such that a surgeon can cut a portion of the femur through the slot, and mill the femoral bone bed by directing the milling tool about the guide. A femoral trial removal clamp facilitates in removing the femoral trial prosthesis, and a spreader compression clamp aids in compressing the final prostheses as the bone cement cures.