It is an achievement coach Brad Stevens, now in his fourth year, thought would take a little longer.
"A couple of years ago I would have thought that would be something we would have to build for a while for," Stevens said. "Obviously we have been lucky to strike on a couple of guys.
"Everyone has a like mind, trying to compete every night. We look forward to the playoffs, then we will look back to what we have accomplished this season."
The Celtics went 25-57 in 2013-14, Stevens' first season in Boston. Now they are contending for first place in the Eastern Conference.
The win enabled the Celtics (50-27) to maintain their narrow first-place lead over the Cleveland Cavaliers in the East.
The Celtics play at Cleveland on Wednesday. The Cavaliers are 2-1 against Boston this season.
The Celtics are tied with Golden State for the most wins (24) since Jan. 25.
"I've been proud of the way that our guys have all gotten better as the year has gone by," Horford said. "I think it's a special thing. Not a lot of teams get to win 50-plus wins in a season and now we have to build on it."
The Knicks (29-48) lost their 11th game this season by a margin of 15 points or more.
The blowout allowed Stevens to rest his starters in the fourth quarter, including Isaiah Thomas, who led the Celtics with 19 points and six assists in just 23 minutes. Jaylen Brown, filling in for Avery Bradley, scored 16 points. .
"I think we're in pretty good shape from a legs standpoint," Stevens said. "There may be a point or two in the next 10 days where we sit guys a little more, but right now we're focused on playing good basketball."
Marcus Smart's 3-pointer started a 10-0 run to begin the fourth quarter, giving the Celtics their largest lead, 98-71, to that point.
Boston built an 88-71 lead going into the fourth quarter.
The Celtics missed three straight 3-pointers towards the end of the first half but still maintained a 60-47 lead at the break. Boston led by as much as 60-41, but the Knicks ended the second quarter with a 6-0 run.
A layup from Thomas capped a 7-0 run, giving Boston a 20-9 lead. He scored 10 points in the first quarter, helping Boston take a 34-23 advantage.
"We were trying to run early offense," said Knicks coach Jeff Hornacek. "We didn't execute quick enough."
NOTES: Celtics F Jae Crowder left the game with a sore elbow late in the third quarter. X-Rays came back negative. "It started tingling, but it's not excruciating pain," he said. "I'm not concerned about it." ... Knicks G Derrick Rose will miss the rest of the season with a torn meniscus that will require arthroscopic surgery. ... The Knicks were without F Lance Thomas (sore hip) in addition to F Carmelo Anthony (back). ... Boston G Avery Bradley missed his second straight game with a stomach illness. Celtics coach Brad Stevens said he expects Bradley back for a key game against Cleveland on Wednesday. ... Boston's scoring average has risen over the last five seasons, from 91.8 points per game in the 2011-12 season to 107.7 this season. ... The Knicks honored their 1999 Eastern Conference championship team. ... Since the 2000-01 season, the Knicks have won just one playoff series, which is tied with the New Orleans Pelicans for the fewest among any NBA franchise. ... New York hasn't won two straight games since Dec. 20 and 22.