Raymond Felton scored a season-high 27 points as the Knicks easily beat the reigning NBA champions despite the absence of the injured Carmelo Anthony.
In last night's other game the Dallas Mavericks hung on to edge the Phoenix Suns 97-94.
New York's Steve Novak scored 18 points as the Knicks won their fifth straight game.
Miami's LeBron James nearly picked up his second straight triple-double - 31 points, 10 rebounds, nine assists - but even that was not enough for the Heat.
Walker gets bronze
BOXING: Kurt Walker, the last Irish fighter in the competition, had to settle for bronze at the AIBA World Youth Championships in Armenia yesterday after losing out to England's Oliver Simpson in the 52kg semi-final.
Walker, who was trailing 9-5 when he answered the bell for the final frame, produced a big finish against the Yorkshire flyweight, but was edged out on a 14-12 decision.
Ireland coach Billy McClean was nevertheless delighted by his charge's performance, saying: "Kurt can be very, very proud of his performance. He had a storming final round and he might have nicked it in the end."
Katie Taylor will tonight collect the AIBA World Female Boxer of the Year Award for a third time in Yerevan, while Michael Gallagher will pick up his second AIBA World Referee and Judge Award.