The invention relates to a cutting device (1) for the placement of a knee prosthesis comprising a bracket (4) and a cutting guide (2) mounted with the ability to move on said bracket (4), wherein the bracket (4) comprises a first marker (43) for identifying it and a fixing element (42) for fixing it to a bone, and wherein the cutting guide (2) comprises a second marker (23) for identifying it and a slot (21) defining a cutting plane suited to guiding a cutting tool. The invention also relates to an assistance device and to a system comprising said cutting device. The invention finally relates to an assistance method and to a computer program product and to a data recording medium for executing the method.
