Periodic Limb Movement Disorder (PLMD) is a sleep disorder characterized by involuntary movements of the limbs during sleep. These movements typically involve the legs and occur in repetitive patterns, often disrupting the sleep cycle. Individuals with PLMD may not be aware of these movements, but they can lead to daytime fatigue and other sleep-related issues. The exact cause of PLMD is not fully understood, but it is often associated with other conditions such as restless legs syndrome and sleep apnea. Diagnosis usually involves a sleep study, where doctors monitor limb movements and sleep patterns to determine the severity of the disorder.