Thirty posterior stabilized total knee prostheses implanted using a computed tomography-free navigation system were compared to a control group of 30 matched total knee prostheses of the same type implanted via a classical, surgeon-controlled technique. The accuracy of the implantations in relation to the mechanical axis in the navigation group was superior to that of the manual group. Early two-year clinical results including range of motion and Knee Society Clinical Rating Score were equally good compared to the manual group. However, potential long-term outcome and functional improvement require further investigation.