The idea that cracking your knuckles can harm you or cause arthritis or whatever is fake. There have been tests done on this and they showed that cracking your knuckles does nothing to you.
That being said, of you see someone ‘cracking’ their ‘knuckles’ constantly, please leave them alone. It’s so annoying and frustrating to be told to stop ‘cracking my knuckles’ because I’ll supposedly give myself arthritis when really I’m putting my subluxing fingers/wrists back in place.