A prosthesis system for replacing a knee joint between a femur and a tibia can include a femoral component, a tibial component, a bearing, a first yoke, and a first key. The femoral component can include a first condylar portion, a second condylar portion, a first sidewall extending superiorly from the first condylar portion, a second sidewall extending superiorly from the second condylar portion where the first and second sidewalls collectively comprise a first hinge portion. The tibial component can have a bone engaging inferior surface and a bearing engaging superior surface. The bearing can have an inferior that engages the bearing engaging surface and a superior femoral engaging surface. The bearing can define an opening. The first yoke can have an inferior portion, a superior portion and a yoke keyway extending through the therethrough.