[KineticLensman]

The knee-jerk effect was documented in the 19th century [0]. I was certainly aware of it when I was young (1970s) although I can't remember whether it was explicitly taught at school, either the effect or the underlying cause.

[0] https://en.m.wikipedia.org/wiki/Patellar_reflex#History

[yencabulator]

What part of that implies the signal does not go all the way to the brain before the reflex happens?