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Periodic limb movement disorder (PLMD) is a condition that causes patients to unconsciously flex or jerk their legs and arms during sleep. The movement may sporadically awaken the patient, which can lead to insomnia or severe daytime sleepiness.

PLMD is marked by characteristic movements that occur during sleep. Patients tend to upwardly flex the big toe, as well as the ankle, knee or hip as often as every 20 seconds. A patient’s legs may also uncontrollably twitch, jerk or kick while sleeping. Some patients may also move their arms. These flexes may occur over a few minutes to several hours.