Abstract
Three important objectives in knee arthroplasty are improving outcome, providing stability and obtaining correct alignment. Alignment has always been described either by anatomically measured alignment (short films, Knee Society Radiologic Score) or by mechanically measured alignment (HKA angle on long leg films). The difficulty of obtaining correct alignment in knee arthroplasty, is that as surgeons we need to find and use anatomical axes and landmarks, in the arthritic and often deformed knee, to align the implant well mechanically. Conventional instruments do the job well for 2/3 of patients, but for 1/3 we need some additional help. Navigation and patient-specific instruments (PSI) should make us more accurate surgeons.
