Abstract: A reference-point providing (RPP) device for conversion of unicompartmental knee arthroplasty (UKA) to total knee arthroplasty (TKA), has a wedge having a joint surface, a bottom flat surface, and a second surface, the second surface extending from the bottom flat surface to the joint surface at a thick end of the wedge and a mounting flange; the wedge fitting in a space remaining after removal of a UKA implant with the joint surface providing a reference point for determining alignment of a TKA implant. Converting a UKA to TKA with the RPP requires removing UKA implant from a femur of a patient, inserting the RPP and attaching it to the femur; using a posterior reference guide having a first paddle on a condyle of the femur and a second paddle on the RPP, to determine necessary alignment and rotation of the TKA implant; and removing the RPP.