Teach-in '98 

The Support Moment

Here are the sagittal-plane moments of force at the hip, knee and ankle joints in normal gait. Positive moments are extensor (i.e. the extensor muscle is active) while negative moments are flexor (flexor muscle active). Click on the picture if you prefer to look at a QuickTime movie.

At first glance, there does not seem to be any pattern, but when the three moments are summed, a somewhat symmetrical extensor curve results, which David Winter* terms the Support Moment:

Winter* noticed that the coefficient of variation (CV) of the support moment (14%) is lower than the individual CVs of ankle, knee and hip (16, 37 and 33%, respectively). Notice, too, that the support moment pattern almost exactly matches the pattern of the vertical ground reaction force:


*Winter DA (1980) Overall Priciple of Lower Limb Support during stance phase of gait. J Biomech. 13: 923-927.
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