The effect of gait speed on the knee adduction moment depends on waveform summary measures

The external knee adduction moment (KAM) is a useful proxy for medial knee loading. Though many studies examining the KAM report the peak value, recent studies have evaluated other measures from this waveform, including the stance impulse. It is important to understand the impact of varying gait speed on discrete values of the KAM waveform when evaluating differences between samples. The purpose of this study was to compare measures of the KAM waveform, including peak and impulse, during level walking at different speeds. Thirty-two healthy participants (mean age=32+/-8 years, 18 women) were recruited. The KAM peak and impulse were calculated over three ambulation speeds: self-selected, slow (15% slower than self-selected) and fast (15% faster than self-selected). To identify differences between these conditions, a one-way repeated measures analysis of variance was utilized. The peak KAM was greater in the fast compared to the slow condition (p<0.05). The KAM impulse was greater in the slow compared to both self-selected and fast conditions (p<0.05). The KAM impulse appeared more sensitive to changes in gait speed because the impulse reflects the duration of loading. These findings highlight that slowed gait speed increased loading exposure on the medial knee tissues, though the maximum magnitude of the exposure was reduced. This trade-off between the increase in duration and decrease in amplitude at slower gait speeds should be examined, particularly where loading exposure may lead to pathology, such as knee osteoarthritis.