Not medical, but make sure that sheets at foot of bed aren't tucked in tightly. I have learned to loosen this when I go to timeshares. When tight, they push my toes down and lead to cramping. Just putting it out there in case the bed was just made, and tucked in tightly. It would explain why all of a sudden...
I had to be on a course of prednisone some months back and experienced the worst cramping of my life. It was the entire leg, toes on up. Has there been any change in meds or diet? I have been on prednisone before and not had this issue, so while I can't definitively point to that, it was the only significant change.
Regardless, good luck. It doesn't seem like cramps should be so painful, but they sure are.