Could be veins
One of the most common symptoms of varicose veins
and venous incompetence is leg cramps.
As much as 70% of the time, people with varicose veins will have leg cramps. Although there are many other possible causes, as others have said, if you have any visible veins in your legs, you should see a venous specialist (phlebologist) for help. Fortunately, it probably isn't a clot.