Unicompartmental knee arthroplasty (UKA) is a successful procedure that is gaining popularity in the United States. Outcomes of UKA depend on careful patient selection as well a meticulous surgical technique and avoiding overcorrection of the preoperative deformity. Intramedullary and extramedullary (EM) cutting guides are available for most commercial systems. EM techniques avoid cannulating the medullary canals of the femur or tibia, thus diminishing the chances of marrow emboli and bleeding from the canal during the procedure. Both with accurate cuts high levels of success with precise component alignment can be achieved when using EM techniques for UKA.