Not quite sure if this is the right forum for the topic, but I stumbled across an article about socks for diabetics on one of my knitting websites. You may not be interested in hand-knit socks, but the article is interesting and there are some more authoritative links to articles at the bottom.
http://www.knitty.com/ISSUEsummer07/FEATdiabeticfeet.html
CynW