Passive and active components of the internal moment developed about the ankle joint during human ambulation

The internal moment developed about a joint during a functional activity is the result of contraction of muscles and the visco-elastic properties of the joint and its surrounding soft tissues. In this study, the contribution of each one of these mechanisms to the total internal moment developed about the ankle joint during human level walking was assessed. The results indicate that during normal level walking the internal moment about the ankle is mainly due to contraction of muscles surrounding the joint. The contribution of the passive component was found to be negligible. These results, however, were found to be different for the pathological case tested. The results indicated that in a subject with a mild equinus ankle deformity, a substantial portion (21%) of the total internal moment was contributed by the passive resistance of the joint and its surrounding structures.