Worldwide experience with the Lcs• mobile bearing total knee prosthesis has been unpar­ alleled both in terms of enduring popularity and outstanding long-term clinical results. Buechel and Pappas's design was based on the principles of; restoring anatomical joint function to as near normal as possible, minimising contact stresses to avoid wear and darn­ age to the bearing surfaces. and finally the idea that constraint should refiect the need for mobility, to avoid shear stresses and loosening of the implant. In 1977, the LCS® knee was implanted by Dr. Frederick Buechel. This was the first mobile bearing, tri-compartmental knee implant. This was also the first to successfully address the key issues ofloosening, wear and patello-femoral problems associated with earlier designs. The unique design solution was the creation of a common articulating geometry for the tibia and patella on the distal femoral surface. This resulted in a tibial and patellar articulation that was mobile in nature, but with an identical radius of curvature and conformity. The mobile bearing concept was considered sufficiently novel and unproven that the US FDA (Food & Drug Administration) required that it be validated in an Investigational Device Evaluation (IDE). An FDA IDE study involving 25 US surgeons was initiated in 1981. Validation of the clinical success of the device in this study resulted in FDA approval of the LCS, Knee (for cemented, tri-compartmental use) in 1985.