To evaluate both the plateau-bone micromotions and the polyethylene-prosthesis micromovements metal markers have been placed on the prosthesis pre-operatively and furthermore into the tibial bone and into the tibial polyethylene during surgery allowing us to evaluate stereo x-rays by a photogrammetric analyses called RSA at the Orthopaedic Center, Aarhus University Hospital. Follow-up stereo x-rays will be scheduled for 1 week, 3 months, 6 month, 1 years and 2 years post-surgery.