Fig. 3

External and knee-internal frontal-plane knee load conditions for static and dynamic situations. Left: The frontal-plane projection of the variable Ground-Reaction-Force (GRF) acting towards the distal end of the tibia over the complete stance-phase of level-walking resembles, regarding its orientation and magnitude in weighted temporal average, much more the GRF of the static single-leg-stand than the GRF of the static balanced two-leg-stand. Similar to the GRF of the static single-leg-stand, the averaged level-walking-GRF approximately points towards the mid-position between both hip centres (Appendix A.1). The average dynamic load-bearing-axis of level-walking thus is markedly different from the Mikulicz-Line. As illustrated for a comfortable walking speed of 5 km/h and average leg length, the midpoint between both hip centres commutes quasi symmetrically around the intersection position of the hip-centre-to-hip-centre connection line with the temporally averaged load-bearing-axis of the predominantly loaded leg (illustration scaled by factor three in width for better visibility). Right: Correlations of the medial compartment force ratio (MFR) measured in vivo over the stance phase of level-walking (including single-leg- and two-leg-phases) with the MFR of the static single-leg-stand and the MFR of the static balanced two-leg-stand, both static situations analyzed over 1.9 s. A 50% MFR at static single-leg-stand involves a 50% MFR at level walking, too