Abstract
For decades, the main cause of failure in total knee arthroplasty (TKA) is still the malalignment of prosthetic components. The authors present a case of advanced knee arthrosis, treated by TKA. Preoperative planning was performed with a mobile application and the patient was submitted to primary TKA using an implant developed with inspiration from the theory of "modified GAP" with a rotated tibial tray. Neutral mechanical alignment of the lower limbs was obtained and the application proved to be viable regarding its proposed plan for this case.