Restless legs syndrome (RLS) is a movement disorder characterized by an uncomfortable sensation or irresistible urge to move your legs that occurs while awake and relaxing. This urge usually happens at bedtime, but can occur at other times when your legs have been inactive, such as sitting still for a long period of time such as riding in a car or watching a movie. To relieve the "creepy, crawly" sensations in the legs, the child or adolescent moves or stretches their legs, tosses and turns or gets up and walks around. The relief is usually immediate upon moving the legs. The cause is unknown but it, too, may be related to low ferritin levels. RLS sometimes runs in families and is thought to be genetic.