Periodic limb movements in sleep are repetitive stereotyped movements of the lower extremities that occur during sleep, consisting of the extension of the great toe with dorsiflexion of the ankle and flexion of the knee and hip. These movements last 0.5 to 4.0 seconds and occur at intervals of 20 to 120 seconds. These movements may be associated with arousals. Only a minority of patients with periodic movements of sleep have excessive daytime sleepiness or insomnia. Patients may be unaware of the movements, but bed partners usually note them.

Periodic movements of sleep have been associated with uremia, peripheral vascular disease, anemia, arthritis, peripheral neuropathy, spinal cord lesions, and the use of tricyclic antidepressants or caffeine.28

Patients with restless legs syndrome (RLS) complain of an unpleasant crawling or deep aching sensation in the legs that is improved by motion of the legs. Most individuals experience these symptoms while sitting or lying down and may complain of the need to walk or continuously move their legs. RLS usually occurs along with periodic movements of sleep. The same factors that provoke periodic limb movements increase the likelihood of RLS.