US Patent 6972039 Floating bearing knee joint prosthesis with a fixed tibial post

An articulating bearing knee including a guide post that in a first orientation allows substantially free varus and valgus distraction, but in another constrains the same. The guide post in includes a superior portion that engages a femoral component of a knee prosthesis in a rotated orientation. When the guide post engages the femoral component it may not distract as if it was not engaged. This allows for a control and constraint of such distraction when the knee is rotated and in a weaker position.