140 patients with knee osteoarthritis scheduled for total knee arthroplasty were randomized to undergo the procedure with either the use of MRI-based or CT-based patient-specific instrumentation. The purpose of this study was to compare the rate of radiographic outliers in the coronal and sagittal planes, as well as the accuracy in predicting component sizing between groups. The results demonstrated no significant differences in outliers of hip-knee-ankle alignment, coronal or sagittal femoral component alignment, or coronal tibial component alignment. A significantly higher rate of sagittal tibial outliers was observed in the CT group compared to the MRI group.