According to Reuben Fine's endgame book, K + R vs K + N (no pawns) is a draw, but Black must be careful to keep his King near the middle of the board because the positions where a mate can occur are all against the edge of the board.
Its a draw unless the knight is on one of the corner squares a8 b8 a7 b7 etc. You might win if he is on one of the rim squares a5 b5 a3 b4 etc. You will end up with a draw if the knight is not in these squares (if both sides play well that is)
King+Rook vs King+Knight Can you win when you play with King+Rook??And can you draw when you play with King+Knight?