## 4 Discussion  
Older adults demonstrated higher knee joint loading confirmed by greater knee adduction moment and joint vertical force. Positive correlations between mean and SD suggest that increased knee adduction moment may be intermittent rather than on every step for the current healthy populations. In contrast, knee vertical force did not show this tendency, possibly indicating that high joint vertical forces may be more prevalent than adduction moment. As physical characteristics such as height and body mass were similar between the two age groups, the observed differences in knee joint kinetics can be attributed to ageing effects on walking patterns. While ageing has been reported to cause shorter step length, larger step width and prolonged double support [20], only increased step width was identified as the ageing effect on spatio-temporal parameters in the current study. This inconsistency can be explained by the fact that older participants in the current study were limited to healthy individuals, capable of walking for 30 min or longer and testing was conducted on an unobstructed laboratory walkway. Although gait parameters were comparable between the two age groups, some foot control variables showed ageing effects, including less toe-out angle, greater time to foot flat and increased step width. Consistent with previous studies [15; 16], correlations results suggested that both reduced toe-out angle and increased step width seen in older adults were associated with lower knee adduction moment. Toe-in gait has recently received attention for its effects on reducing knee adduction moment, possibly due to foot internal rotation preventing tibial abduction and shortening moment arm [2]. Traditionally, eversion support during early stance was considered to reduce moment arm of knee adduction moment and lateral wedge shoe-inside is widely recognised as the footwear intervention to ever the ankle and reduce adduction moment [25; 26]. It is, therefore, possible that both eversion and internal rotation of the ankle during early stance may be effective in reducing knee adduction \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & & \multicolumn{2}{c}{**Add Moment**} & \multicolumn{2}{c}{**Vertical Force**} \\ \cline{3-6}  & & **Young** & **Older** & **Young** & **Older** \\ \hline \multirow{4}{*}{**Knee joint kinetics**} & **Adduction Moment** & - & - & - & - \\ \cline{2-6}  & **Adduction Moment (SD)** & 0.552 ** & 0.795 ** & \(-\)0.389 * & \(-\)0.288 \\ \cline{2-6}  & **Knee Vertical Force** & \(-\)0.405 * & \(-\)0.199 & - & - \\ \cline{2-6}  & **Knee Vertical Force (SD)** & 0.346 * & \(-\)0.020 & 0.068 & \(-\)0.180 \\ \hline \multirow{4}{*}{**Foot motion**} & **Foot Contact Angle** & 0.223 & 0.511 * & \(-\)0.271 & \(-\)0.358 \\ \cline{2-6}  & **Foot Contact Angle (SD)** & \(-\)0.078 & 0.212 &.084 & \(-\)0.031 \\ \cline{2-6}  & **Toe-out Angle** & \(-\)0.182 & 0.422 * &.097 & 0.007 \\ \cline{2-6}  & **Toe-out Angle (SD)** & \(-\)0.064 & 0.292 &.071 & 0.162 \\ \cline{2-6}  & **COP Displacement** & \(-\)0.047 & 0.250 &.064 & 0.052 \\ \cline{2-6}  & **COP Displacement (SD)** & \(-\)0.110 & \(-\)0.003 & \(-\)0.212 & \(-\)0.194 \\ \cline{2-6}  & **Time to Foot Flat** & \(-\)0.005 & \(-\)0.037 & 0.276 & 0.318 \\ \cline{2-6}  & **Time to Foot Flat (SD)** & \(-\)0.184 & \(-\)0.002 & 0.269 & 0.295 \\ \hline \multirow{4}{*}{**Spatio-temporal parameters**} & **Step Length** & 0.113 & 0.258 & \(-\)0.445 ** & \(-\)0.703 ** \\ \cline{2-6}  & **Step Length (SD)** & \(-\)0.347 * & \(-\)0.082 & 0.045 & 0.052 \\ \cline{2-6}  & **Step Width** & 0.174 & \(-\)0.426 * & \(-\)0.282 & 0.074 \\ \cline{2-6}  & **Step Width (SD)** & \(-\)0.095 & \(-\)0.005 & 0.156 & 0.021 \\ \cline{2-6}  & **Double Support Time** & 0.056 & 0.052 & 0.139 & 0.352 \\ \cline{2-6}  & **Double Support Time (SD)** & \(-\)0.155 & 0.016 & 0.220 & \(-\)0.027 \\ \hline \hline \end{tabular}
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