You photo looks pretty symmetrical to me. I would suggest perhaps you are functionally rolling in on one site. If you are a runner get someone to video you running and this might show more about what is going on and where. You need to look carefully at both sides as often an issue presenting on one side may be due to an insufficiency on the other. Callous formation under the foot (bug toe area) and show wear may also highlight what is going on over time.