Does がくがく refer to shaking in general, or shaking of the knees?


I'm asking because I've been searching for anime scenes that involve the knee-
shaking trope. がくがく came up, but I'm not sure if that refers to knees shaking
specifically or just regular trembling. If not, does anyone know how to say
"shaky knees" in Japanese.




[**がくがく**](https://dictionary.goo.ne.jp/jn/38619/meaning/m0u/)

> **１** 固定されていないで緩んでいるさま。ぐらぐら。「奥歯ががくがくする」
>
> **２** 寒さや恐ろしさ、疲労などで、からだの一部が小刻みに震えるさま。「脚ががくがく（と）震える」「ひざががくがくする」

This mimetic word chiefly depicts that something hard and is supposed to be
immobile rattles due to loosened fixation. When applied to human movement,
it's suitable to represent a rectilinear kind of shake the way joint would do,
while a similar word
[ぶるぶる](https://dictionary.goo.ne.jp/jn/196232/meaning/m0u/%E3%81%B6%E3%82%8B%E3%81%B6%E3%82%8B/)
stands for those have convulsive impression. Thus while one of its typical
usage is to describe shaking knees, it's not limited to that, as you can see
from the dictionary entry above.

We can just say 膝ががくがく（する） to mean "have shaky knees", or if you're sure you
want a noun phrase, 震える膝 is for "shaky knees".

