One I never really got as I never saw the original use of the phrase. I get the idea, but am uncertain how it came to be that people found it funny.
And I dislocated my kneecap last year. As minor an injury as that is (compared to my mother getting her whole knee replaced), I can assure you that knees are not all that easy to fix. Surgery is quick and commonplace, but the recovery takes a long time and a lot of work to exercise the tissue properly. Even still, I can't perform a couple of kicks without risk of reinjury.
