In my mother-tongue, there's a word that describes this act. I'm searching for an idiom/phrase or whatever that describes this without any ambiguity.
This sound comes when someone twists the body part that contains joints. Making this sound out of knuckles is quite common. Also, imagine Bruce Lee in the ring and just before the fight is started, he twists his fingers, rotates his head and stretches his legs and all of these gestures will produce a special sound--a cracking sound--but I'm not sure about using this word. If there's a 'crack' sound, medically, it's a hairline fracture! Being a healthcare provider, I have heard/used this word that way. :)
What that sound is called? or in that way, what do we call that act?
And please mind it, I'm not just referring to knuckles but any joint in the body.