Restless legs syndrome (RLS) is a sleep disorder in which a person experiences involuntary urges to move their legs as well as unpleasant sensations in the legs, usually in the calf area. These sensations may be described as creeping, crawling, tingling, pulling, or painful. They may be felt anywhere from the thigh to the ankle. One or both legs may be affected. For some people, the sensations are also felt in the arms. People with RLS have an irresistible urge to move the affected limb when the sensations occur. Some people, however, have no definite sensation, except for the need to move. Sleep problems are common with RLS. The condition often makes falling asleep difficult. Throughout the night, people with RLS may suffer from sleep fragmentation and disruption of restorative sleep cycles. RLS affects about 12 million adults in the United States. The cause of RLS is still unknown. Some cases are believed to be inherited. If you have a family history of RLS, you may develop the condition earlier than someone with no family history of the condition. You can also develop RLS as a result of the following: neurological diseases, a pinched nerve root in the lower back, kidney dialysis, pregnancy, chronic diseases such as Parkinson's disease, iron deficiency, certain medications, alcohol, and caffeine. Your doctor can diagnose RLS based on your symptoms, a complete medical history, and a physical exam. In addition, lab tests or a sleep study may be performed. Currently, there is not a definitive test to diagnose RLS. The National Institutes of Health has drawn up a list of symptoms that describe the syndrome and can be used to diagnose it: A desire or urge to move the limbs, often caused or accompanied by unpleasant sensations. You may feel pain deep inside your legs. Worsening of symptoms at rest. You feel the urge to move or have unpleasant sensations that begin or worsen during periods that make you drowsy, including resting, lying, sitting, or otherwise being inactive. Some people have the urge to move and the unpleasant sensations after any long period of inactivity, such as during flights and while sitting in the theater. Symptoms are partially or totally relieved by activity, such as walking or moving around. When you move, symptoms improve immediately, and relief continues for as long as you are active. The symptoms may recur as soon as you stop moving. Symptoms fluctuate during the day. You may tend to feel the most discomfort late in the day and at night. The symptoms of RLS affect people differently. They can occur only occasionally, or only in certain situations, or they can be frequent. They can range from mild to intolerable. RLS can start at any age, but most people are middle-aged or older. RLS responds well to various treatment strategies. Maintaining good sleep habits can help relieve symptoms. Other treatment options for RLS may include avoiding activities that worsen symptoms, maintaining a well-balanced diet, and taking approved medications for the condition.