An implantable orthopedic knee joint prosthesis includes a femoral component having an internal box geometry defined by a bone-engaging surface configured as a primary prosthesis. The femoral component has a threaded bore therein communicating with the bone-engaging surface. An adapter has a mating surface complementary to the box geometry of the femoral component and an internal box geometry defined by a bone-engaging surface configured as a revision prosthesis. A hole through the adapter is aligned with the threaded bore of the femoral component and has a recessed shoulder. An adapter screw has a head and a threaded shank, the head sized to be received within the hole of the adapter in engagement with the shoulder, and the shank being sized to be threadedly received within the threaded bore of the femoral component. The adapter screw includes a threaded bore therein. A spacer has a mating surface complementary to the box geometry of the adapter and an internal box geometry defined by a bone-engaging surface configured as a revision prosthesis. The spacer has a hole therethrough aligned with the threaded bore of the adapter screw. A spacer screw has a head and a threaded shank, the shank being sized to be threadedly received within the threaded bore of the adapter screw.