look up any word, like blumpkin:
 
1.
Black knees belong to women who meet random strangers in places of gathering (i.e. restaurant or nightclub) and proceed to give them blowjobs.
Jenny: She was blowing some dude in the bathroom at the club.
Mike: Explains why she in the club with a white dress and black knees.
by naggernensky May 16, 2009
 
2.
The characteristic discolouration of the patella of black women. The colour is literally black, in contrast to their skin pigmentation, which, as we all know, is actually brown.
"Why have you got de black knees, mon?"
by Aprileen Alexander October 24, 2006