Sleep-related movement disorders include several diseases that share the common symptom of involuntary muscle contractions during sleep. These contractions can be in the legs, such as restless legs syndrome (RLS; Willis-Ekbom disease) or sleep-related leg cramps. Movements can be seen in the whole body, such as rhythmic movement disorders, or minimal, such as in bruxism. Certain medical conditions can trigger these sleep-related movement disorders.