Hoshi K, et al. - This study was intended to ascertain the rotational motion of each component at full extension and flexed positions during a squatting activity after total knee arthroplasty (TKA). Researchers performed a cross-sectional study (level 4) including individuals with severe knee osteoarthritis scheduled to receive TKA. They analyzed 13 knees of 11 individuals after mobile-bearing TKA (NexGen LPS-Flex, Zimmer Inc.) at 10 weeks and 1 year postoperatively. This analysis estimated rotation of the femoral component relative to the insert (FEM/INS) and tibial component (FEM/TIB) as well as insert rotation relative to the tibial component (INS/TIB) during flexion. In this study, repeated measure 2-way ANOVA and post hoc test was applied. During a squatting activity, it was noted that the mobile-bearing insert enhances the compatibility of FEM/INS in extension; the amount of INS/TIB rotation is significantly smaller than that of FEM/INS. This information indicates to surgeon to take caution to conduct TKA with a fixed insert in which 6.3° of rotational offset would be added to the rotational alignment at FEM/INS at full extension.