It can't. "Tu lo sai" refers to something (you know) not to someone (you know).
So, "Tu lo conosco"?
EDIT Oh yeah "Tu lo conosci" thanks for catching that dnovinc
if the "tu" is before the verb does that mean that its not question. i'm trying to recognize verbal cues...but with this robot voice its hard (at times) to distinguish questions from statements.
The difference between questions and statements is whether the intonation at the end of the sentence goes up, which means it's a question. The robot voice does not do an adequate job with intonation, unfortunately, so no it has nothing to do with pronoun placement. Technically, you do not need pronouns at all in statements or questions, since the verbs are already conjugated, which is not the case in French and German, though.