The last 10 years has seen the development of Computer Aided Navigation for Total Knee Replacement.  This has been advertised as "more accurate" but there is little evidence that this is the case.  Knee replacement which is instrumented off of the center of the tibia and the center of the femur is highly accurate and does not rely on pins which are visualized by the computer aided process from across the room.  In addition, because the pins are close to the knee itself, any tiny error introduced by bumping a pin may easily throw off the measurements.  The error is then magnified because of the small width of the knee in comparison to the length of the tibia.  In this author's opinion, this is now simply a triumph of technology over reason.  I have an Engineering Background and understand the dangers of reliance on tools which can be inaccurate creating a false sense of security.  In general, simple is better.  These systems are quite costly and add to surgical time adding little to improved accuracy.  The future may bring more accurate means to Surgically Navigate with computer assistance in a reliable way.  With current technology this is simply a marketing gimmick.  Only you and your surgeon can make this decision.  Ask questions and be informed.