The purpose of this study was to compare the range of motion (ROM) of conventional total knee arthroplasty (TKA) using high-flexion, posterior cruciate ligament (PCL) stabilized prostheses and the ROM of conventional knee arthroplasty using navigation-assisted TKA, with mobile-bearing, cruciate ligament-retaining knees. Fifty conventional TKAs with high-flexion knees and 50 navigation-assisted TKAs with mobile-bearing knees were included in this study. The ROM and number of knees that allowed comfortable kneeling and cross-legged sitting 2 years postoperatively were evaluated and compared. Functional outcomes of the two groups were assessed with the Hospital for Special Surgery (HSS) scores. The authors found no difference between the ROM and functional outcomes of conventional TKA with high-flexion knees and navigation-assisted TKA with mobile-bearing knees.