BOSTON — A brilliant rivalry was renewed Thursday night, with all the attendant tension, drama, ill will and ear-splitting volume.

And at the end of a long evening of "Beat L.A." chants, the Boston Celtics had their first NBA finals victory in 21 years, a convincing 98-88 defeat of the Lakers at TD Banknorth Garden to open this best-of-seven series.

Paul Pierce and Kevin Garnett battered the Lakers all night, Pierce doing so on a sprained right knee that briefly forced him to the locker room in a wheelchair in the third quarter.

So while the Lakers and Celtics restarted a rivalry that had been dormant since 1987, Pierce borrowed a chapter from another historic finals moment, doing his best Willis Reed impression.

Pierce scored 22 points, but first gave all of New England a mild heart attack: With 6 minutes 49 seconds left in the third, Pierce was carried off the court, clutching his right knee, after getting bumped in mid-air by his teammate Kendrick Perkins. For a moment, it appeared that he might be done for the night, if not longer.

But Pierce returned, to an ecstatic roar, a few minutes later, having missed less than 2 minutes of game time. He promptly walked to the scorer's table (big roar), checked back into the game (bigger roar) and drew a foul on Kobe Bryant, who smacked Pierce in the face while lunging for the ball (big, angry roar).

The volume doubled moments later, when Pierce hit back-to-back 3-pointers, giving the Celtics a 75-71 lead.

"That was a big momentum change in the game," Lakers coach Phil Jackson said.

Pierce scored 15 points in the third period, and the Celtics never trailed again.

"I heard my knee pop and thought I tore it," Pierce said, "but I needed to be out there for my team." Up until that point, Garnett (24 points, 13 rebounds) had carried the load, while Pierce and Ray Allen (19 points) took turns misfiring. But Boston's swarming defense held Bryant in check for most of the night, and left the Lakers searching for other options.

Bryant finished with 24 points but went 9 for 26 from the field and committed four turnovers. Derek Fisher and Pau Gasol each scored 15 points for the Lakers, who shot 5 for 20 in the fourth quarter.

Coach Doc Rivers said he feared the worst when Pierce first went out and approached it cautiously when he came back in.

"If he didn't move right," Rivers said, "I was going to take him out."

The Celtics took an 86-78 lead, their biggest edge of the night, early in the fourth quarter. The building shook as Garnett saved a ball in the backcourt and in midair flipped it back to Sam Cassell for a wide-open jumper. A moment later, James Posey hit a 3-pointer for the 8-point edge, forcing the Lakers to call timeout with 8:42 to play.

Fisher and Sasha Vujacic hit jumpers to cut the deficit in half, but the Lakers then went cold. They missed seven straight attempts during one stretch, before Lamar Odom plowed through P.J. Brown for a layup and a 3-point play, making it 90-85 with 2:57 left.

This is the Lakers' fifth finals appearance of the decade, the Celtics' first since 1987, when they last battled Los Angeles for the title. The off days have been filled with nostalgia and recollections of the last 10 times these teams met in the finals.

No one minded indulging history, particularly, the Celtics, who are happy just to have ended a two-decade finals drought.

"I think it matters," Rivers said of the rivalry. "I don't know how much, but when you play for the Celtics, you get a history lesson, and our guys know the Celtic history since the day they've walked in the door. So I do think it matters."

Boston took an early seven-point lead while the Lakers waited for Bryant to find his game. He missed six of his first seven attempts — all of them jumpers, most of them 15 feet or beyond — and took only two foul shots. Fisher was the Lakers' most effective option, scoring 11 points in the second quarter. He combined with Odom and Gasol for a late surge that gave the Lakers a 51-46 halftime lead.

Garnett generally dominated the half, alternately bullying Gasol and Odom while scoring 16 points.

Rajon Rondo added 10 points. The Celtics' other stars, Allen and Pierce, combined to go 3 for 12 from the field.

The Celtics closed the regular season with the NBA's best record, and earned home-court advantage for this series, but still entered the finals as underdogs — in Las Vegas odds and in public perception.

"Like I told them at the start of the year, the questions will never stop," Rivers said. "They'll never stop about Rondo, they've never stop about me, they'll never stop about Kevin, they'll never stop about Paul, they'll never stop about our team, and you can't take it personally. It's part of it. Just go out and just keep playing, and that's all you can do."