Just saw a patient in the office with the complaint of increased ankle sprains since he got his new orthotics. He stopped wearing them since he thought maybe they were the cause.
This is a patient with a significant forefoot valgus, not fully compensated for in weight bearing resulting in a inverted hindfoot, cavus foot. The devices do contour his arched well NWB, but standing on them actually appear to invert him more. Also the heel cup is rather shallow .
Thoughts, when constructing orthotics for a cavus foot type:
this is a laterally unstable foot, so anything to give the foot a pronatory torque will assist in stabilizing the foot – lateral flange, rearfoot post laterally not beveled, full length or forefoot only valgus wedge … couple this with a deep heel cup for added support.