On the interpretation of the support moment.

It has been suggested by Winter (J. Biomech. 13 (1980) 923-927) that the 'support moment', the sum of the sagittal extension moments, shows less variability in walking than any of the joint moments separately. A simple model is put forward to explain this finding. It is proposed to reformulate the definition, in the sense that hip and ankle moment are now weighted with a factor 12, and knee moment with a factor 1. It can be shown that this version of the support moment depends only on the magnitude of the ground reaction force and the knee angle. It is plausible that it will show comparatively little variation in walking.