Tibiofemoral kinematics around heel strike associated with heel strike transient in patients after total knee arthroplasty

This is the authors' abstract. We don't add key points for this paper.

Background Heel strike transient (HST), an abrupt increase in vertical ground reaction force (vGRF) following heel strike (HS), has been reported in patients after total knee arthroplasty (TKA). However, the contribution of swing-to-stance tibiofemoral kinematics to HST remains unclear. This study examined the relationship between tibiofemoral kinematics during this transition and HST after TKA. Methods Seventeen patients who underwent TKA were analyzed using force plate measurements and validated 2D/3D registration. Tibiofemoral kinematics, including knee flexion angle, rotation, and anteroposterior (AP) translation, were calculated immediately before and after HS. HST was defined when post-HS vGRF did not rise gradually but showed a distinct transient peak with a peak-to-subsequent-minimum ratio of ≥1.2. Results Patients were classified into the HST group (n = 8) and non-HST group (n = 9) according to the presence of HST. Two-way analysis of variance revealed a significant interaction between group and gait phase for flexion angle ( P < 0.01). Post-hoc analysis revealed a significant decrease in flexion angle after HS ( P < 0.01) in the HST group. For lateral AP translation, a significant main effect of group was observed ( P = 0.036). No significant group-related differences were found in internal/external rotation or medial AP translation. Conclusions Compared with the non-HST group, the HST group showed a greater extension-directed change in flexion angle and a more anterior position of the lateral contact point across the before- and after-HS. These findings suggest that HST is associated with a distinct tibiofemoral kinematic pattern during the terminal swing-to-early stance transition.