(L-R) Boston Celtics Kevin Garnett guards New York Knicks Kenyon Martin as he goes up for a shot against Celtics Courtney Lee during the first half of Game 6 of their NBA Eastern Conference semifinal playoff basketball series in Boston, Massachusetts May 3, 2013.?[Photo/Agencies]

Knicks advance for first time since 2000 with 88-80 victory

Kevin Garnett made his way off the court toward Boston's locker room looking straight down the entire way, not lifting his head or even a hand to the fans crowding him and reaching for a high-five or to congratulate him.

There was nothing to celebrate. The Celtics' season was over, ending in an 88-80 loss to New York that clinched the first-round playoff series for the Knicks in six games.

Even a run of 20 straight points in the fourth quarter wasn't enough for the Celtics to push a series they trailed 3-0 to a final game.

"We were just trying to grab some momentum and just fight," Garnett said. "We were just trying to push for the last time. That's what it was."

Nobody for Boston pushed harder than Garnett, who finished with 15 points and 10 rebounds. It wasn't enough to overcome a dreadful shooting night for the Celtics.

Boston cut a 26-point deficit to four points twice down the stretch, but failed to pull off one more improbable run.

"Right now a lot of emotions, a lot of thoughts go through your head about the season, about what you could have done better tonight to keep the season going, about the future," Paul Pierce said after struggling to a 14-point night. "It's a lot of mixed emotions right now. It's a tough loss."

Carmelo Anthony scored 21 points, including a clutch 3-pointer after the Celtics pulled within four late in the fourth quarter to help the Knicks hang on and advance in the postseason for the first time since 2000.

Iman Shumpert scored 15 of his 17 points in the second half for the Knicks, but the Celtics cut a 75-49 deficit to four points. But Anthony made a jumper to give New York an 81-75 lead and followed with a 3-pointer, then J.R. Smith converted a three-point play to restore the double-digit lead the Knicks had nursed most of the game.

The Knicks will open the Eastern Conference semifinals against the Indiana Pacers in New York on Sunday.

Jeff Green scored 21 points for the Celtics, who had rallied from a 3-0 series deficit and had a chance, at home, to force a decisive seventh game.

No NBA team has advanced in the playoffs after losing the first three games.

Pierce scored 14 points on 4-for-18 shooting, making one of nine 3-point attempts. Anthony also struggled from inside and outside the arc, going 7 for 23 from the floor and missing his first four 3-point attempts - that was 19 in a row in the series - before sinking the key basket with 1:43 to go.

The Knicks had not won a playoff series since Patrick Ewing and Latrell Sprewell (and current backup center Marcus Camby) helped them reach the 2000 Eastern Conference finals.

The Celtics now face another offseason of talk whether to break up the aging core that won the franchise's record 17th NBA title in 2008 and returned to the finals two years later.

Garnett said it was too soon to consider his future.

"I haven't really thought about it to be honest with you," he said. "I'm kind of digesting the current."