Orthostasis...a quick definition I found and it is funny in a way

[Lazarus]

Standing, also referred to as orthostasis, is a human position in which the body is held in an upright ("orthostatic") position and supported only by the feet. Although seemingly static, the body rocks slightly back and forth from the ankle in the sagittal plane. The sagittal plane bisects the body into right and left sides. The sway of quiet standing is often likened to the motion of an inverted pendulum.[1]

I am researching autonomic dysfunction in MS and found this ..

[Virginia]

Too funny! I use to tell my PCP of long ago that I felt like my body was moving when I stood up. I told him it was swaying like I had just come off a boat. He would say his usual "ehmmm". This was when I was trying to find out what the heck was wrong with me. Well, maybe it was going back and forth, just more pronounced for me.