Periodic Limb Movement Disorder (PLMD) is an “independent disorder of repetitive, highly-stereotyped limb movements that occur during sleep.”1 It involves both the repetitive movements and an associated sleep disturbance or fatigue that is believed to be caused by the movements.
Many people experience periodic limb movements during sleep (PLMS) that are stereotyped and repetitive, and primarily involve the person’s legs. PLMS is common and many normal sleepers experience these movements without either being aware of them or experiencing any ill effects. These individuals would not be diagnosed with PLMD, which is characterized by limb movements that result in significant sleep disturbance or impairment in the person’s life.
1 Thorpy M, “Classification of Sleep Disorders,” in Kryger M, Roth T, Dement W (ed.), Principles and Practice of Sleep Medicine (5th Edition), St. Louis: Elsevier Saunders, 2011, page 686.