I'll reiterate what Kyle and JJ said. Go see your doctor if this continues. He/she can run some blood tests to ensure you're not deficient minerals or vitamins ie: Magnesium, Calcium, etc.
If you're diagnosed with MS as Kyle says...etc.
Good luck
Lisa
As JJ mentioned, we are an MS focused bunch :-)
If you are diagnosed with MS, or suspect it for other reasons, wha you describe can be spasticity, neuropathic pain or a combination of the two. Both can be MS related.
In any case I would suggest that you see your doctor.
Kyle
I'm not sure if your aware but you've posted your question in the MS community, this link may help in explaining this to you.......
http://www.foot-pain-explored.com/foot-cramps.html
Cheers...........JJ