I don't know for sure what's the problem, but you could try soaking your feet(or your whole body!) with Epsom Salts
The magnesium in it might loosen/relax those muscles and pull out toxins. I usually will add in some borax also... It's safe as table salt
(it is a salt), it's anti-fungal and seems to give the epsoms salt more drawing power.
Hope it helps. : ) Feel better.