The knee is left... A bk amputation allows saving the knee and usually some part of the tibia bone that goes down to the foot. This will also allow the prostheses to be less complex and more functional because the entire knee joint is not part of the prosthesis. Of course, if the pathology present in the leg requires an ak amputation, the surgeon will inform you; but it's always better to save the knee if possible.
Below the knee. A below the knee amputation is a type of amputation which will spare the knee and enough of the lower leg to allow for the use of a below the knee prosthetic device.