The knee joint prosthesis includes a tibial component and a femoral component. The tibial component has a top surface, a bottom surface opposite to the top surface and a first slot passing through the top surface and the bottom surface for accommodating a cruciate ligament. The tibial component has at least one first protrusion disposed on the bottom surface, and the first protrusion has a plurality of first through holes. The femoral component is carried by the tibial component and has a second slot for accommodating the cruciate ligament. The femoral component has at least one second protrusion disposed on a surface thereof opposite to the tibial component, and the second protrusion has a plurality of second through holes. The first protrusion has a first rear and front portions, and a width of the first protrusion gradually becomes thicker from the first rear portion toward the first front portion.
