Members do not see these Ads. Sign Up.

Hey all

I was just looking at these two cast I had done yesterday and I thought it was worth considering how the foot shape might affect the stability about the STJ



You'll notice that they are both the same length but on is much more narrow, the distance from the ground to the STJ axis is about the same although you can't judge that by these pics. So you might imagine this is like the difference between the stability of a block of 4x4 and a knife standing on it's edge. The block is mechanically stable whereas the knife is unstable about its longitudinal axis. Therefore forces applied to resist any rotational instability could be or should be applied at different points i.e. see the diagram below:



In the block the force f produces the same moments about p as the force f1 but in the knife example the moments by force f about p is not equal to the moments by force f1 about p. This may be an important consideration when considering the deformation forces or the design of an orthotic appliance.

Regards Dave

 

How much consideration should be given to whether the narrow foot is a natural genetic expression or environmental development from wearing tight shoes?