What physiological trait would make it impractical for someone to wear flat shoes?

So, I have a character who has an interesting quirk: they cannot wear flat shoes or boots (i.e. where the heel is at the same level as the ball of the foot or approximately so, within 1.27cm or so) without risking pain/injury to their feet and legs. What sort of physiological trait or "defect" would cause this in an otherwise normal human being? Said trait can be heritable or idiosyncratic, but needs to be present from birth or young age, should not interfere with their ability to walk/run when suitably shod, and should not affect the appearance of their feet in any clearly noticeable way.

posted over 8 years ago

Shalvenay‭

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