What would chairs look like if our knees bent the other way?The latter question is the easier of the patella-oriented queries, so let me answer it with the following diagram:
Do penguins have knees?
So yes, Emily, there is a knee. It is the joint between the femur and tibiotarsus/fibular pair.
In that case, it seems that some variation of a Swedish kneeling chair would work best.
Just as the kneeling chair directs most of the downward force of the body along the length of the femur, our hypothetical reverse-kneed people would sit in a similar fashion, but the lower halves of their legs would extend out and up with a slight bend.