The foot and ankle is an often complicated and neglected part of the body. When we run through the skills at FASTER, we look at each bone in turn through the body, with an end goal of getting you the ability to predict motion. In theory, by the end of learning the HMAC, you should be able to predict every bone motion in space, around its axis, every joint feeling from this, in all planes with the reasoning why AND how each muscle around the joint you are focusing on, and up and down the chain of muscles, joints and bones will react.
Not to want to sound too simplistic, the foot and ankle should be a pretty easy part of the body to predict. It has 26 bones, 33 joints, 107 ligaments, 19 muscles and tendons sat inside that unit below your leg, but that does not make it complicated so much as fun to learn. The great thing about the foot, is related to movement around the body. When you make a movement, then the foot is really easy to predict, as I have tried to show here –
Right foot loading (collapsing, or pronating) and the left foot unloading (firming for take off, or supinating)
The foot and ankle is easy to predict, because however it happens, when the tibia ends up being rotated in, more than the calcaneus, then the foot and ankle starts to pronate. On a solid floor, the front of the foot (the midtarsal joints being those we look at, at faster) make predictable motions as well, and so muscle reactions are easy to see and evaluate too. If the tibia ends up rotated out more than the calcaneus, then the foot starts supinating, and the mid foot follows.
For something different to happen, then an obvious force would need to be present (either a floor change, or the foot being off of the floor). The movements happen because of the structure of the subtalar joint.