Restless leg syndrome is a persistent urge to move the legs that typically happens at night or in the evenings while lying or sitting down. The urge is usually sparked by an uneasy feeling in the legs that is temporarily relieved every time you move your legs. The condition can be severe enough to disrupt sleep.
Anyone can suffer from restless leg syndrome, also called Willis-Ekbom disease, although it is more common in older women and tends to get worse with age. The National Institute of Neurological Disorders and Stroke estimates that the disorder affects 10 percent of people  in the United States.
To date, the precise cause of restless leg syndrome has not been narrowed. The condition is thought to be caused by a lack of coordination between the central and peripheral nervous systems. It might be caused by an imbalance in dopamine, a neurochemical that regulates muscle movement.
Although the cause is still unknown, researchers have linked the disorder to certain health conditions and genetic predisposition.