Also known as shaky legs syndrome, this is a rare movement disorder with characteristics of fast, task-specific tremor, affecting the legs and trunk while standing. The prevalence is unknown. To date, around 390 cases have been reported in the literature. Women are predominantly affected (sex ratio: 2:1) with disease onset occurring in middle aged or elderly people. At present, the pathophysiology is unknown. The disorder is sporadic but exceptional familial cases have been reported.