PHILADELPHIA – Kevin Garnett turns 36 on Saturday, a youthful age for any man, except for the rare ones with nearly 55,000 punishing minutes absorbed on an NBA floor.

Garnett knows all the ageist labels attached to the Boston Celtics. How they’re called The Over The Hill Gang, and the wisecracks about flashing AARP cards before they check into a game, and how each postseason game raises questions about The Big Three’s last hurrah.

The Celtics know a title run with Garnett, the 36-year-old Ray Allen and 34-year-old Paul Pierce is on its last legs.

Aging legs, yes. But far from finished.

Garnett displayed dominant proof in Boston’s Game 3 rout against the Philadelphia 76ers. He scored 27 points and grabbed 13 rebounds to help the Celtics snare a 2-1 lead in the Eastern Conference semifinals.

The Sixers had no way to slow Garnett, who made 12 of 17 shots in Game 3 and is shooting 63 percent in the series.

Let others get nostalgic for the stretch run of Boston’s terrific trio. Garnett only cares about winning the next game, the next series, and another championship to pair with the one The Big Three clinched in 2008.

“I’m focused on the playoffs,” Garnett said Thursday. “I haven’t given much thought to it. I’m definitely aware of it. We know what the possibilities are. But at this point, right now, it’s the playoffs.”

Garnett heard a few screams of “We love you, Kevin!” from passing fans as he answered questions alongside Pierce outside the team hotel.

The chants should be more antagonistic in Game 4 tonight in Philadelphia.

Garnett will tune them out the way he’s zoned out the light attempts at defense the Sixers have thrown at him. Even at his age, Garnett is more mobile than Philadelphia’s frontcourt combo of Spencer Hawes and Elton Brand. Lavoy Allen’s foul troubles have limited his guarding Garnett.

“You have to do a better job early,” Sixers Coach Doug Collins said. “You can’t let him get such deep position. You can’t let him run underneath the rim, turn and face the basket. You have to meet him at the free- throw line.”

Pierce was slowed by an injured left knee until a 24-point, 12-rebound outing in Game 3. Allen scored only three points, and has been secure enough in letting Garnett, Pierce and Rajon Rondo handle the scoring load that he turned down Garnett’s offer to get him more touches.

Garnett told Allen: “We’ve got to do whatever we can to get you open.”

“I looked at him and said, ‘Kevin, you’re the guy getting shots. You’re the guy that’s scoring. We just won by 20. I don’t need to, for the sake of my ego, do anything like that. We just keep doing what we’re doing. If they keep guarding us this way, then you’ve got to keep doing what you’re doing.”‘

Pierce realizes a sense of urgency to win a title with the trio playing their final games together. They want to make it last.

“We’ve realized that from Day 1. I think pretty much the last couple of years we’ve been feeling like that,” Pierce said. “But the influence is to try and win another championship, regardless of if this is going to be our last time together. Who knows what the future is going to hold for all of us?”