100 patients scheduled to undergo primary total knee arthroplasty (TKA) were randomized to undergo the procedure using either a new pinless computer navigation system or a conventional technique. The purpose of this study was to examine the accuracy of this new system for implant alignment. Results indicated that there was a significant difference in favour of the new pinless computer navigation system for alignment at the coronal femoral-component angle (CFA), and the percentage of outliers for all three radiographic angles (i.e. hip-knee-ankle, coronal femoral-component, and coronal tibia-component angles). The two groups were similar with respect to duration of surgery, and alignment at the hip-knee-ankle and coronal tibia-component angles.