With blood flowing and bodies flying, the Celtics showed the Knicks they will be tough to beat next month if this was in fact a preview of a first-round playoff series.
Paul Pierce scored 21 points and Ray Allen had 15 for Boston despite a poor shooting night and a nasty cut on his head that briefly forced him from the game.
Carmelo Anthony scored 22 points for the Knicks, but neither he nor Amare Stoudemire had a field goal in the fourth quarter. Chauncey Billups had 21 and Stoudemire finished with 16.
Boston (50-19) matched its victory total from last season after coming into play tied with Chicago for the best record in the Eastern Conference, seizing control in the final minutes with its trademark tough defense and the sensational all-court play of Rondo, who made the tiebreaking basket with 3:10 left.
The Knicks lost for the sixth time in seven games and fell to 7-9 since acquiring Anthony last month, and as with Miami's occasional struggles this season, has created concerns about how long it takes a team to figure things out when it has put superstars together.
"Hopefully two, three years," joked Celtics coach Doc Rivers, who has his reasons for that wish.
The longtime Atlantic Division rivals could be headed toward a meeting in the first round of the playoffs. New York entered in seventh place in the East, a half-game behind Philadelphia.
This one started to resemble a playoff scrap in the second quarter. Boston's Troy Murphy had to come out of the game with a bloody nose, and Glen Davis crashed to the court after Anthony caught him in the head with an elbow after grabbing a rebound.
Then Allen had to leave briefly in the third quarter after his head was bloodied by Jared Jeffries' elbow while going for a rebound. Allen wiped blood from his head on the court with a towel, not far from where his mother was seated next to Spike Lee in the front row of courtside seats.
The Celtics took the hits and kept coming, trimming New York's lead to 69-63 on Glen Davis' layup at the third-quarter buzzer. They were down nine after Billups' four-point play with 7:26 remaining but stormed back with 13 straight points, going ahead 86-82 on Garnett's jumper with 4:20 to go.
The Knicks tied it, and after Rondo's layup with 3:10 put Boston back ahead, Anthony was cut above the eye after colliding with Rondo trying to steal and inbounds pass. Rondo came up with it as Anthony fell to the court, then found Davis for a layup and a 90-86 edge with 2 1/2 minutes left.
Pierce knocked down a jumper for a six-point lead, and Allen put it away with a dunk to make it 94-86 with 40 seconds to go. He closed it out with two free throws.
A day after the Knicks managed nine points in the first quarter at Milwaukee, their worst opening period since scoring a franchise-low five on Nov. 21, 1956, against Fort Wayne, Stoudemire had nine by himself after 12 minutes Monday as New York built a 25-22 lead.
The Knicks scored the first seven of the second, capped by consecutive baskets by Ronny Turiaf, to open a double-digit cushion. It grew to 45-30 on Billups' 3-pointer with 3:41 remaining in the half, and the Knicks took a 51-37 advantage to the locker room.
Notes
The teams meet again in Boston on April 13 in the regular-season finale. … Shaquille O'Neal worked out on a stationary bike before the game, though it's still unknown when he will return from a sore right leg that's sidelined him since Feb. 1. … The Knicks started Turiaf at center, the third straight game they had a different starter at that position.