## 3 Results  
The resulting kinematic behavior of the TF joint was changed within the different MB design variants during the squat motion (Figure 5). The medio-lateral translation, femoral anterior-posterior translation, and tibofemoral contact force showed almost no differences between MB design variants I and II. However, for MB design variant III, the kinematic pattern was considerably different compared to the other two MB design variants. The peak femoral anterior-posterior translation value for all design variants occurred between flexion angles of 15\({}^{\circ}\)-30\({}^{\circ}\). For design variant III, the peak value of 2.9 mm occurred at 18\({}^{\circ}\) knee flexion. The first two design variants (I and II) showed the peak value of 2.8 mm after 20\({}^{\circ}\). Variants I and II showed a similar behavior concerning the femoral anterior-posterior translation (Figure 5A). However, variants I and II showed considerably less femoral anterior-posterior translation compared to variant III. For instance, during the squat motion, we detected a posterior translation of 12.6 mm (variant II), whereas variant III showed a posterior translation of 16.8 mm at 90\({}^{\circ}\) knee flexion. Furthermore, the paradoxical anterior translation of variant III ceased in an earlier flexion range. The pattern of the mediolateral translation was similar between variants I and II, but there were differences compared to variant III in which the amount of the mediolateral translation was  
Figure 5: Tibofemoral kinematics and kinetics during the dynamic squat motion for the three mobile-bearing (MB) total knee replacements (MB design variants I, II, and III). Evaluation of the femoral anterior(+)-posterior(\(-\)) translation (**A**), tibial medio(\(-\))-lateral(+) translation (**B**), tibial insert rotation with respect to the tibial tray (**C**), and tibofemoral contact force (**D**). higher (Figure 5B). Concerning the commercially available variant I with a rotation pin and end stops, the end stops affected the mechanically possible internal-external rotation of the tibial insert relative to the tibial ray (Figure 5C). In this regard, we detected a maximum difference by more than 5\({}^{\circ}\) compared to variants II and III. Design variants II and III showed the maximum value of external rotation at 13\({}^{\circ}\). The resulting tibiofemoral contact force during the squat motion remained nearly unchanged between the three variants (Figure 5D). However, during early knee flexion (30\({}^{\circ}\)-40\({}^{\circ}\)), the tibiofemoral contact force increased by more than 250 N for design variant III. Concerning the modeling strategies, compared to the six DoF baseline, the two DoF joint captured the kinematic pattern well in the case of all three MB design variants (Figure 6). The maximum deviations occurred mostly at the end of the squat motion. Only slight deviations were observed for the tibial insert rotation (Figure 6(CI-CIII)), e.g., for design variant III the deviation was less than 1\({}^{\circ}\) at 90\({}^{\circ}\) knee flexion. Most of the deviations in calculated kinematics for the different modeling strategies occurred after 50\({}^{\circ}\) flexion. However, for design variants I and II, the deviations also occurred during mid-flexion. As mentioned above, the amount of deviation for all investigated parameters was low. While the differences between the modeling strategies were minor, the computation time was remarkably decreased in the case of the two DoF joint model with translational end stops for all three MB model design variants (Figure 6(DI-DIII)). For design variants I, II, and III, the computation time decreased by 68% (167 min), 80% (307 min), and 82% (278 min), respectively, when using the two DoF joint modeling strategy compared to the six DoF baseline modeling strategy. Figure 6: Tibiofemoral kinematics during the dynamic squat motion for the three mobile-bearing design variants I-III in case of two modeling strategies with different joint topologies (first: six DoF baseline; second: two DoF joint).