It is an abnormal sensation of spontaneous, unbearable pain that occurs in the lower extremities. It is most common in the gastrocnemius muscle, and can occasionally occur in the thighs or upper extremities, usually symmetrically. Patients often complain of tearing, crepitus, tingling, burning, pain, or itching in the deep parts of the lower extremities. Patients have an urgent and intense feeling of needing to move and this leads to hyperactivity. Symptoms occur at rest and can be partially or completely relieved by activity. Normally, symptoms become intense at night while lying in bed and peak after midnight, forcing patients to kick their legs, move their joints or massage their legs, often describing “not having a comfortable place to put their legs.” In severe cases, the patient has to get up and walk constantly to get relief. Insomnia is a natural consequence, and most patients experience periodic limb movements during sleep; PMS is a stereotyped, repetitive flexion of the legs that occurs during REM sleep and can wake the patient. As a result of nocturnal sleep disturbances, patients suffer from severe daytime sleepiness and reduced work capacity.