Burning sensation under my feet

I have been having constant burning and tingling sensation under my feet ( more on my left foot ). Sometimes, I experience some pins and needles feeling too. Mot of the times, I had to remove my shoe to get relief. Though the feeling is more at the night time, it has been there constantly throughout the day. The general physicians and the Podiatrists that I have visited ruled out any diabitic / pinched nerve causes after detailed examination. I would appreciate if you can throw some light on this. Thanks, – Kris