Effect of variable contact area on knee articular dissipation during 3D gait analysis

Values for tibiofemoral contact area used in simulations to represent in vivo conditions are usually approximated from data taken from in vitro experiments. However, it is uncertain that in vitro data could represent perfectly in vivo conditions. The aim of this study was to analyse the sensitivity of the outcomes of a model calculating knee joint dissipation during gait to a change of tibiofemoral contact area taken from in vitro experiments from literature. The sensitivity of four different outcomes corresponding to three articular dissipative mechanisms was analysed by varying the tibiofemoral contact area by a constant. These mechanisms are referred to frictional drag, intrinsic viscoelasticity and surface friction. Differences in the magnitude of the maximum peaks reached during gait were analysed. Varying tibiofemoral contact area yielded negligible changes (< 1%) for the frictional drag and the intrinsic viscoelasticity mechanisms and minor changes (1--4%) for the surface friction mechanism. The dissipative model was found to be insensitive to a variation in tibiofemoral contact area.