You require an evaluation by a vascular specialist, who will probably order a color dopplar. This painless and non-invasions and involves running an ultrasound probe and receiver up and down the leg while the image is displayed on a CRT. The most common cause is circulatory, and a diagnosis of what is called intermittant claudication is likely. The pulses of the feet must be evaluated. There are various treatments, ranging from inserting a balloon into the blood vessel to enlarge the diameter, to a replacement of a vessel or insertion of mesh to keep it open.. A hematologist consult is in order to rule out problems such as too high a hematocrit or malformed erythrocytes that are clogging up the blood vessels. On a short-term basis, good hydration, a baby aspirin a day and 1000 mg of omega-3 fish oil may provide some relief. Sometimes there is co-factor, such as a calcium and vitamin D-3 deficiency, however from the symptoms you describe the problem is likely to be vascular. Have this evaluated as soon as possible, because serious life-threatening problems may develop that can be forestalled by appropriate intervention.
Could be a multitude of things....rule out potassium deficiency first by eating banana's. If that does not work then I would visit the doctor for vascular diagnosis.
Yes, I agree with you on the potassium deficiency. It is a frequent cause of leg cramps.