80 patients scheduled for total knee arthroplasty were randomized to undergo the surgery using either patient-specific instrumentation (PSI) or computer-assisted surgery (CAS) navigation technology for guiding bone cuts. The purpose of this study was to compare the incidence of intraoperative and postoperative outliers between groups for component alignment. Intraoperative results demonstrated a significantly higher incidence of coronal tibial alignment and tibial slope outliers in the PSI group compared to the CAS group, with the intraoperative abandonment of PSI required in 7 patients (17.5%) who were excluded from further analysis. Postoperative results at 3 months continued to demonstrate a significantly greater number of tibial slope outliers in the PSI group compared to the CAS group.