Abstract: A device for setting a total knee prosthesis includes: a tensioning component (1) having: a tibial plate (2), a slide (5) mobile along a rail (3) and elements (6, 11) for being fixed to an ancillary component including a centro-medullar rod and a tibial plate and capable of receiving variable-width wedging elements; and a motoring elements (8, 10) for tensioning the knee when the plate is applied on a tibial section and the ancillary component (20) secured to the slide, a perforating guide capable of being mounted on the rail (3) and having drilling holes; the guide capable of including or of being associated with a member for palpation of the anterior part of the femur; and locating elements (EF) for determining the interarticular space available in flexure, thereby enabling the distal femoral section plane or the posterior section plane to be accurately determined.