Abstract: A three piece prosthetic knee joint comprised of a femoral component in the form of a shell member having convex condylar portions with an insert having a top surface with concave portions which receive said condylar portions of the femoral component and a bottom surface that rotatably engages a platform load bearing tibial component. The device may also include a cam mechanism between the insert and the tibial component so that lateral motion therebetween lifts the tibia thereby more nearly simulating natural knee joint action than can be obtained by existing two component prosthetic knee joints.The present design is also adapted to provide a total knee joint replacement system whereby a single surgical technique may be employed, and then the correct components may be inserted according to the observed condition of the knee.