What does the brain teaser 'knee ur full of' mean?

KNEE

UR FULL OF

You're full of baloney/bologna. This is derived from the fact that "ur" is a chat abbreviation for "your" and the phrase "ur full of" is below "knee". When you pronounce it, it sounds like "you're full of baloney". Baloney is a colloquial name for bologna - you're full of baloney/bologna is a slang term.