The influence of stance-phase knee flexion on the vertical displacement of the trunk during normal walking

Objective: To determine the effect of stance-phase knee flexion on the trunk's vertical displacement in normal walking. Subjects: Three able-bodied adult male volunteers. Design: Kinematic data describing the joint centers and joint angles of the legs and pelvis were collected from the subjects. The subjects walked at four target speeds (range, approximately 1.0 to 2.0m/sec); a minimum of three trials of data at each walking speed were collected and processed. Setting: Clinical gait analysis laboratory. Results: Stance-phase knee flexion was not found to significantly reduce the peak-to-peak amplitude of the trunk's vertical displacement in normal walking. The reason for this has to do with the timing (ie, phase) of the stance-phase knee flexion wave with respect to the trunk's vertical displacement during the gait cycle. Stance-phase knee flexion in normal walking was found to reduce the mean elevation of the trunk by a few millimeters and to delay the trunk's vertical displacement waveform by about 2% to 6% of the gait cycle from where it would have been otherwise. Conclusions: Contrary to conventional wisdom, stance- phase knee flexion does not appreciably reduce the amount of vertical movement of the trunk in normal walking.