## 3 Results
The percentage of reduction in the maximal posterior pelvic tilt during the OA limb step was significantly higher in the TKR group compared to the NTKR group (\(p\) = 0.032). In addition, the percentage of change of the flexion-extension range of the hip in the CL limb was significantly higher in the TKR group compared to the NTKR group (\(p\) = 0.041). Lastly, the percentage of change of the knee flexion-extension range for the OA limb was higher in the TKR group compared to the NTKR group (\(p\) = 0.006). The percentage of change of the perturbed gait characteristics are summarized in Table 3. There were no significant differences between the two groups in the percentage of change between the baseline and the follow-up tests for all spatial-temporal parameters. As for the kinematics, when the CL limb was perturbed, the percentage of reduction in the maximal OA hip extension was higher in the TKR group compared to the NTKR group (\(p\) = 0.031). When the OA limb was perturbed, the percentage of change in the maximal flexion-extension range of the OA knee was lower in the TKR group compared to the NTKR group (\(p\) = 0.011). In addition, there was a marginal difference in the percentage of change of the maximal ankle plantar flexion (\(p\) = 0.049). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{1}{c}{**Parameter**} & **NTKR (_n = 17_)** & **TKR (_n = 14_)** & \(p\) & **t** \\ \hline \multicolumn{6}{c}{Contralateral limb tripped} \\ \hline Stance duration & 91.4 (76.1–102.3) & 91.1 (74.6–126.0) & 0.312 & 1.030 \\ Step length & 19.4 (4.8–38.6) & 22.2 (9.8–38.2) & 0.188 & \(-\)1.356 \\ Base width & 89.1 (75.6–146.2) & 130.6 (98.5–160.6) & 0.989 & 0.014 \\ CL hip maximal extension * & \(-89.9\) (\(-110.1-(-37.4)\)) & \(-106.5\) (\(-157.8-(-88.4)\)) & 0.323 & \(-\)0.989 \\ OA hip maximal extension & 19.4 (161.9) & \(-234.8\) (252.7) & 0.031 & \(-\)2.937 \\ CL knee maximal flexion * & \(-9.5\) (\(-49.4-53.8\)) & \(-187.7-(-843.7-29.6)\) & 0.569 & \(-\)0.570 \\ OA knee maximal flexion & \(-3.0\) (34.2) & \(-11.9\) (43.7) & 0.244 & 0.563 \\ \hline \multicolumn{6}{c}{Injured limb tripped} \\ \hline Stance duration & 77.9 (73.6–116.9) & 85.3 (75.8–139.9) & 0.219 & \(-\)1.260 \\ Step length & 15.7 (6.5–77.1) & 41.3 (16.5–169.6) & 0.069 & 1.996 \\ Base width & 110.8 (66.7–142.2) & 97.2 (76.3–142.7) & 0.167 & \(-\)1.430 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Spatiotemporal and kinematics data of the lower limb of the perturbed gait immediately after the perturbation and the first step following the perturbation calculated by \(X[\%]=\frac{X_{relative-p}-X_{baseline}}{X_{baseline}}\).100. Numeric values are presented as the average and standard deviation. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{1}{c}{**Parameter**} & **NTKR (_n = 17_)** & **TKR (_n = 14_)** & \(p\) & **t** \\ \hline \multicolumn{6}{c}{Contralateral limb tripped} \\ \hline Stance duration & 91.4 (76.1–102.3) & 91.1 (74.6–126.0) & 0.312 & 1.030 \\ Step length & 19.4 (4.8–38.6) & 22.2 (9.8–38.2) & 0.188 & \(-\)1.356 \\ Base width & 89.1 (75.6–146.2) & 130.6 (98.5–160.6) & 0.989 & 0.014 \\ CL hip maximal extension * & \(-89.9\) (\(-110.1-(-37.4)\)) & \(-106.5\) (\(-157.8-(-88.4)\)) & 0.323 & \(-\)0.989 \\ OA hip maximal extension & 19.4 (161.9) & \(-234.8\) (252.7) & 0.031 & \(-\)2.937 \\ CL knee maximal flexion * & \(-9.5\) (\(-49.4-53.8\)) & \(-187.7-(-843.7-29.6)\) & 0.569 & \(-\)0.570 \\ OA knee maximal flexion & \(-3.0\) (34.2) & \(-11.9\) (43.7) & 0.244 & 0.563 \\ \hline \multicolumn{6}{c}{Injured limb tripped} \\ \hline Stance duration & 77.9 (73.6–116.9) & 85.3 (75.8–139.9) & 0.219 & \(-\)1.260 \\ Step length & 15.7 (6.5–77.1) & 41.3 (16.5–169.6) & 0.069 & 1.996 \\ Base width & 110.8 (66.7–142.2) & 97.2 (76.3–142.7) & 0.167 & \(-\)1.430 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Spatiotemporal and kinematics data of the lower limbs of the unperturbed gait calculated by \(X[\%]=\frac{X_{relative-p}-X_{baseline}}{X_{baseline}}\).100.