Accuracy of implant positioning and precise reconstruction of leg alignment offers the best way to achieve good long-term results in total knee arthroplasty. Computer instrumentation was developed to overcome the inherent limitations of mechanical instrumentation, improving the final position of the component and restoring the normal mechanical axis of the lower limb. Current navigation systems use either optical or electromagnetic tracking both having advantage and disadvantage. Knee navigation systems are not yet universally accepted in the orthopedic community, and their cost/benefit ratio remains a matter for further discussion. Despite and high number of clinical trials demonstrating that Computer-assisted navigation is a tool which makes possible the accurate and reproducible performance of a total knee procedure, we have to observe at the moment an absence of high quality endpoint studies demonstrating a longer implant survival in contraposition of standard technique. The current methodology of tracker systems and the anatomical referencing of the patient's landmark are probably the main sources of the limitation of the eventual systems. Finally the cost/benefit ratio of the computer assisted technology remains a matter of debate.