Its funny you should mention that, my son complains of pain and stiffness in his feet and his feet are compleltely flat---no arch.  I always wondered if this was because he was quite over suppressed from learning to walk.  I assumed since we take all our weight onto our feet and since there is bone loss, that the bones that take the most weight and do a lot of work with walking probably are the most likely to take some considerable bashing where that's concerned.  I took him to a Podiatrist to get his feet looked at some eyars ago as the flat feet had started to affect his knees--- naturally----when your feet turn in like that it affects your knees and then the rest of the posture ---so I was concerned that all this may give him problems.  I note that he is most comfortable wearing sport shoes that have some arch support.  He hates other shoes.  here, kids tend to walk around in jandals (slip ons) or sport sandals anyway so now in summer, I put him in the sport sandals and in trainers/running shoes in the winter.  If I buy him anything else, it is taken of and left after a short time and never worn.  Adults can get the support inserts but they do not make them for children---though the podiatrist offered to take a cast of his foot and make some up---I thought it would be too expensive to get this done every six months when I have to buy shoes anyway--as kids feet are growing all the time. 

I note in the last year---his feet look a little better for it and with wearing the support where it is needed, his posture and everything is looking a lot better.  He doesn't complain of the aching in his feet either as much as he used to.

JH