[yorkieusa]

I really don't know. Muscle cramps can also be a sign of tapeworms, too. Low magnesium can cause muscle cramps.

You are saying it looks like muscle cramps, but could pain be causing the muscle to tighten? If so, I would have her checked for Lyme disease:

Lyme Disease Symptoms:

In dogs, Lyme disease produces symptoms characterized by arthritis, though it can sometimes involve heart, nervous system and the kidneys. The arthritic joints may become swollen and hot, and there may be a fever (102 to 105 degrees) and poor appetite. Dogs may also become lame because of the disease. This painful lameness often appears suddenly and may shift from one leg to another. If untreated, it may eventually disappear, only to recur weeks or months later. The glands (lymph nodes) of the dog may also be swollen.

I just thought I'd make a few suggestions in the hope that something may help you. Let us know how things go.