I found the following phrase in a book I was reading：
I will personally send agents to your house to remove your kneecaps in the dead of night.
I am confused about the meaning of remove your kneecaps. Does this mean cut down the kneecaps? Or does kneecaps mean others?
I know the author's meaning, he wants to express his fuss. But why use remove your kneecaps, is there some allusion?