Thanks for being nice Roger :)

Granted, our terminology is a bit different and I use the term "collapse" as a dynamic one, not necessarily permanent. The reason your feet grow as you age is because your arch IS dynamic and does fall a bit as the years of standing on your feet accumulate. Your forefoot also widens, your toes develop crazy osteophytes from years of wearing shoes, etc. As far as muscle growth, there are VERY few muscles of any consequence in your foot itself. They are called intrinsics, and while they are certainly very important, they are relatively inconsequential in terms of foot bulk.

But long bones absolutely do not grow in length once growth plates are closed. It is impossible.

As for the hip muscles not controlling the rotation of your leg, I again beg to differ Roger. It is NOT the realm of the unfit…it is the primary impairment of marathon runners. Most of you who have knee pain after running or hiking have pathologically weak hip rotators. And if your knees start to bother you at the end of a hike, or a run, then your hip rotators and abductors simply don't have the endurance they need. It's because they are relatively small support muscles and are not worked very much during forward motion activities. So if you're a runner, or a hiker on somewhat tame surfaces, those frontal plane stabilizing muscles don't get much of a workout.

And the end of a hike, or a long run, or a long walk, then try to do a single leg squat and see where your knee goes. Does it fall in a bit? It's your gluteus medius and the external rotators of your hip that control that. And continuing down the chain, those muscles also play a major role in the support of your arch.

As for our ancestors marching around in sandals or barefeet…those would be some nasty looking feet. Very flat. Calloused. Broad in the forefoot. Calves would be huge (that's where the muscles that control your feet are). People who grew up wearing shoes outside, and most of the time in general…we have nice dynamic arches that absorb force when you bear weight (by literally sinking closer to the ground, thus lengthening your foot) and returning to neutral when you are not. Over time of yes, very unusual stress of a thru hike (very few people in modern day western culture walk that much – I am on my feet literally ALL day and I walk maybe 8 miles a day). So walking with increased weight on your back, day after day after day after day…for months – yes, that arch is going to get quite a workout and some people are not going to recover from the increase in stress, the broadening of the space between bones in the forefoot.

Does that make sense?