Periodic Limb Movement Disorder (PLMD) and Restless Legs Syndrome (RLS) By Richard J Schwab, MD, University of Pennsylvania, Division of Sleep Medicine Reviewed / Revised May 2022 | Modified Sep 2022 View Patient Education Symptoms and Signs Diagnosis Treatment Key Points Periodic limb movement disorder (PLMD) and restless legs syndrome (RLS) are characterized by abnormal motions of and, for RLS, usually sensations in the lower or upper extremities, which may interfere with sleep.