Below mentioned are the causes for the leg cramps
1) Cramps may occur because of decreased amounts of minerals, such as calcium and magnesium
2) Exposure to cold temperatures, especially to cold water.
3) Other medical conditions, such as blood flow problems (peripheral arterial disease), kidney
disease, thyroid disease
, and multiple sclerosis
4) Standing on a hard surface for a long time, sitting for a long time, or putting
5) Being dehydrated, which means that your body has lost too much fluid.
Most likely cause in your case seems like a LOW CALCIUM in blood. I advice you to have it checked.