The two-time defending champions were seven points behind with just over four minutes still to play in the fourth quarter, but Ray Allen and Dwyane Wade made a series of shots to add 11 unanswered points for the hosts.
James Anderson had a chance to set Thaddeus Young up to level the scores in the final moments of the game, but he fumbled the pass and the ball went out of bounds, condemning the Sixers to their 23rd straight defeat, while the Knicks are unbeaten in eight.
The Brooklyn Nets made it three wins in a row as they eased to victory against the Brooklyn Nets.
Joe Johnson scored 27 as the home side opened up 10-point lead by half time, before pulling ahead further in the third quarter.
Anthony Davis, who was struggling with a respiratory infection, scored 13 of his 34 in the final 12 minutes to secure a win for the visitors.
Results in full: Chicago Bulls 79-91 Indiana Pacers, New York Knicks 93-92 Philadelphia 76ers, Oklahoma City Thunder 119-118 Toronto Raptors, New Orleans Pelicans 111-105 Atlanta Hawks, Boston Celtics 98-114 Brooklyn Nets, Memphis Grizzlies 86-91 Miami Heat, Denver Nuggets 106-122 Dallas Mavericks, Detroit Pistons 92-98 Phoenix Suns, San Antonio Spurs 99-79 Sacramento Kings, Washington Wizards 117-107 Los Angeles Lakers