There are many definitions of orthostatic tremor on the internet based on old information, we think that this definition sums up the new research well.
Orthostatic tremor (OT) is a rare, chronic disorder characterized by unsteadiness on standing accompanied by a fast (13–21 Hz) leg tremor . The tremor decreases significantly on sitting or walking . The urge to sit down or to move can be so strong that patients eventually avoid situations where they may have to stand still, such as shopping or queuing, and instead have to keep moving . Many orthostatic tremor sufferers have the fast (13-21Hz) tremor in the arms which can be found when the limbs are weight bearing independent of stance [3, 4, 5]. Whilst the act of standing rarely results in falls, the disturbance of the balance system gives rise to falls due to over balance,especially when over-tired . OT sufferers can suffer from stiffness , dizziness , and bodily sway , depression , unsteadiness  and gait problems in severe cases, [11,13] such as wide based gait, slightly stooped and sometimes freezing; in general the condition is progressive in many patients . The act of standing can give rise to pain in the legs and the lower back in many sufferers . Currently there is no cure or effective treatment for OT and the condition can have a serious affect on a patient’s quality of life [8, 12].
Primary Orthostatic Tremor or OT as it is usually called is a very rare degenerative neurological condition first diagnosed by Dr K. M. Heilman back in 1984 and his report detailed the state of a very small group of sufferers. It is thought that OT is so rare that only about a couple of hundred cases might exist in the UK.
According to the National Organization of Rare Disorders the following is a brief description of Primary Orthostatic Tremor.
Primary orthostatic tremor is a rare movement disorder characterized by a rapid tremor in the legs that occurs when standing. The tremor disappears partially or completely when an affected person is walking or sitting. Individuals with primary orthostatic tremor experience feelings of unsteadiness or imbalance. In many cases, the tremors become more severe over time. The exact cause of primary orthostatic tremor is unknown.
Now that description comes from only a handful of medical reports and very few subjects, in fact it is rare to see a report where more than twenty took part in the study. What this means is the very few reports on the internet have been copied over and over again and physicians believe that the description above outlines the condition, where as many specialist know that the description only describes the onset conditions and if the patient is unlucky then they progress to much worse symptoms.
What you have to remember with OT is that it is rare, most physicians have never heard of OT unless they have had a patient with the condition. Worse still only about a third of neurologist have heard of the condition and after reading the standard description they are often confused when faced with a sufferer who have progressed to more severe symptoms.
1 Heilman KM. Orthostatic tremor.Arch Neurol
2. Britton TC, Thompson PD, van der Kamp W, et al. (1992) Primary orthostatic tremor: further observations in six cases. J Neurol 239:209–217
3. Natural History and Syndromic Associations of Orthostatic Tremor: A Review of 41 Patients. W. Gerschlager MD.A. Munchau, MD, R. Katzenschlager, MD, P. Brown, MD, FRCP, JC. Rothwell, PhD, N. Quinn, MD, FRCP, AJ. Lees, MD, FRCP,4,5 and KP. Bhatia, MD, FRCP
4 Fitzgerald PM, Jancovic J. Orthostatic tremor: an association with essential tremor. Mov Disord 1991;6:60–4.
5 Clinical and Neurophysiologic Spectrum of Orthostatic Tremor: Case Series of 26 Subjects P. Piboolnurak, MD, Q. P. Yu, PhD, and Seth L. Pullman, MD, FRCPC
6 Effective Treatment of Orthostatic Tremor With Gabapentin V Gerald H. Evidente, MD, C H. Adler, MD, PhD, J N. Caviness, MD, and K A. Gwinn, MD
7 Vertigo – a practical approach J Grobbelaar, MD ChB, MMed: CME Sept 2012 Vol 30 No.9
8 Quality of life in patients with orthostatic tremor: Gerschlager W., Katzenschlager R., Schrag A., Lees AJ., Brown P., Quinn N., Bhatia KP.
9 Orthostatic Tremor Inducing Instability _ Raquel Manrique-Huarte, Juan Arcocha, Nicolás Pérez-Fernándeza
10 Carpenter MG, Frank JS, Silcher CP. Surface height effects on postural control: a hypothesis for a stiffness strategy for stance. J Vestib Res 1999;9:277–286.
11 Pramipexole is a possible effective treatment for primary orthostatic tremor: M Finkel
12 Orthostatic Tremor Significantly Affects Quality of Life: J. Eric Ahlskog, M.D., Ph.D., Neurology, Mayo Clinic
13 Associated movement disorders in Orthostatic Tremor: J Neurol Neurosurg Psychiatry doi:10.1136/jnnp-2012-302436