Kasparov Vs. Karpov Mistake?

In this match, it would appear that Karpov played a move that ruined his chances badly.  I might be looking into this on surface level stuff, but Instead of saving his queen, he offers his queen for 6 points, Karpov gives up his queen for a knight? (Moves 22-30)

Now the question is, did Karpov make the right move?  If he took the rook then he would be at a loss of 4 points.  The play he did currently show on move 24 grants Karpov with a loss of 3 points. Should he have instead moved his knight  in the way?

These two players are highly skilled at the fine game of chess and can see beyond what I can see for sure, but I believe there could have been a better way for Karpov to play.

All opinions are welcome.  I'm sure I will be shown up at some point and someone will be able to explain why moving a piece in the way would have been a poor choice, but that's what I am looking for. :)