The clinical use of ceramics in total knee replacement was first reported by Langer in 1972, when an uncemented alumina ceramic tibial platform was used. The first uncemented alumina ceramic combined with ultrahigh molecular weight polyethylene total knee replacement system appeared in Japan. The system was later modified in design for cemented fixation (KOM-1, 2, and 3). Other alumina ceramic TKA systems with UHMWPE, such as the KC-1, TSD, NCU, LFA-I, and YMCK, have also been clinically used in Japan. There are even designs using metal femoral condyles with alumina ceramic articulating surfaces, thus avoiding direct contact between ceramic and bone. Zirconia ceramic femoral condyles have also been used in Japan (Bi-surface, KU). The cobalt-chromium alloy femoral condyle-based Multigen Knee System has also begun to introduce a femoral prosthesis in AMC (BIOLOX?delta), without changing the design. After 12 months of follow-up, the BIOLOX?delta ceramic femoral condyles (MultigenPlus) had good clinical scores and no loosening of the prosthesis was seen. Figure 3 shows some of the ceramic knee designs that can be found on the market. It is far more difficult to compare wear rates at different interfaces in TKA than in THA. prosthesis design has a strong influence on wear, such that relevant data can only be obtained from in vitro wear studies with the same design and different interface materials. For example, the wear of a zirconia femoral condyle of the Bi-Surface system (Kyocera, Corp, Kyoto, Japan) and a cobalt chromium femoral condyle of the same design was compared to the wear of UHMWPE on the Shore-Western knee simulator. The results showed that the UHMWPE wear rate of the zirconia prosthesis was, on average, 4 times lower, whereas the surface roughness (Ra) of the cobalt-chromium femoral condyle was 5 times higher than that of the zirconia femoral condyle. In addition, the wear rate was related to the radiation dose when the UHMWPE was sterilized with gamma radiation. In another study in which the UHMWPE sterilization method, the type of knee simulator, and the measurement parameters were different from those described above, the wear rates of the alumina femoral condyles, zirconia femoral condyles, and cobalt-chromium alloy femoral condyles of the Biosurface Knee System were compared with respect to UHMWPE. The results remained similar, with the ceramic prosthesis showing an average 5-fold decrease in wear rate, while the alumina ceramic prosthesis showed a lower wear rate than the zirconia ceramic. Damage was observed on the surface of the cobalt-chromium prosthesis but not on the ceramic prosthesis. In addition, a study was conducted to compare the performance of cobalt-chromium versus AMC femoral condyles against UHMW knee systems against three-body wear by performing 5 million cycles of motion on a knee simulator. No damage was seen on the surface of the ceramic component and less wear was seen on the UHMWPE pads compared to the cobalt-chromium femoral condyles. In clinical applications, first-generation TKA ceramic prostheses showed a high loosening rate due to uncemented fixation and inadequate osseointegration. However, a few well-fixed alumina ceramic and zirconia ceramic prostheses performed well clinically. Several designs of alumina and cobalt-chromium alloy femoral condyle removal prostheses (6 to 23 years in humans) were studied and analyzed for wear and surface damage. The cobalt-chromium femoral condyles were found to have more surface damage and higher roughness, which was consistent with the in vitro experimental results. The UHMWPE pads that formed the joint with the ceramic femoral condyles showed less wear.