I don't think of Adriana as a particularly clumsy child. In fact, I think she's quite well coordinated for her age. But she is an active little girl and takes her fair share of tumbles. As a result, her knees are frequently a bit banged up--one of them always seems to have a scab.
Still, I thought she knew what her knees were. She points to any body part you ask her to, her knees among them. She follows along when I sing "Head and Shoulders, Knees and Toes." But the other day she pointed to a scrape on her ankle and told me "knee." I guess she was less clear on what exactly her knees were than I thought.