Since the Prior Art (conventional ski boot tongue) shown in FIG 2 in my last post did not show the movement of the shin in forward ankle flexion (dorsiflexion) I have marked up the drawing below to show the line of the front of the shin (red dashed line) before and after flexion. The pink box at the lower end of the shin shows how the shin gets jammed in the throat of the boot shell as the ankle flexes forward. In a future post I will show with an animated video sequence how the throat of the boot shell acts as lever that acts to force the base of the tibia rearward as the aspect of the tibia at the top of the boot cuff moves forward. I think it probable that this mechanism played a role in boot top fractures in the old leather ski boots because it causes the muscles in the back of the leg to reduce contractive force or turn off completely leaving the tibia and fibula without protection from the force of the forward fall that is attempting to bend it.Screen Shot 2014-02-13 at 10.44.53 AM