Night time leg cramps or “Charlie horses” can be a source of significant discomfort and impair one’s ability to either fall asleep or remain asleep. For many years cramps were treated with muscle relaxants, sleeping pills or quinine tablets, often without any attempt at finding out what the underlying cause was. Venous insufficiency may cause night time leg cramps secondary to the movement of water and protein (serum) out of the muscles at night when the legs are no longer dependent. During waking hours when sitting, standing or walking are the dominant positions, the legs are dependent and high venous pressure from leaking vein valves, forces water and protein out of the veins into the surrounding muscles, skin and fat of the calves.
The more swelling one develops over the course of the day the more liquid there is to move out of the muscles at the end of the day once the legs are even with the heart (lying down in bed). The lymphatic system is the third system of vessels in the circulatory system (the other 2 are arteries and veins) and are responsible for scavenging the escaped liquid form the tissues such as muscles and fat and returning this liquid (serum) back to the venous system at the level of the left clavicle (collar bone) where the thoracic lymphatic duct joins the left internal jugular vein. It is postulated that the movement of water out of the muscle compartments of the calf creates an electrolyte imbalance causing muscle cramps.
Dr. Magnant Speaking on Nighttime Leg Cramps