BOSTON — Isaiah did it for Chyna.

On his late sister’s birthday, Isaiah Thomas honored her memory with a career-high 53-point night in the Boston Celtics’ 129-119 overtime victory over the Washington Wizards in Game 2 of the Eastern Conference semifinals on Tuesday.

Thomas lost his sister Chyna in a one-car accident in their home state of Washington on April 15. Every day since has been an uphill struggle for the 5-foot-9 superstar.

“She would have been 23 today, so the least I can do is go out there and play for her,” Thomas said after scoring 20 points in the fourth and nine in overtime to give his team a 2-0 series edge at TD Garden.

“There was no way I couldn’t play on her birthday. I wanted to win for her.”

Making his feat all the more impressive is the fact that Thomas had a six-hour dental procedure one day before to replace a tooth he lost during the team’s Game 1 victory Sunday.

“What else is there to say?” Celtics coach Brad Stevens said. “There was a point today where he was not feeling good at all. He’s had a tough day and I thought he was going to really have to gut this one out. Not only guts it out, he ends up with 50. Pretty impressive.”

Not only were Thomas’ 53 points a personal best, but they were the second-most points a Celtics player ever scored in a playoff game behind John Havlicek’s 54 on April 1, 1973.

Pretty impressive for a franchise with 17 championships.

Still, Thomas is keeping his head on straight.

“It’s nice (for) your name to be in Celtics’ history with all the great players, but until you win one of them championships you can’t call yourself a great player,” Thomas said.

Thomas’ previous career playoff high was 42 points against the Atlanta Hawks in last year’s first round. He scored a regular-season career high of 52 against the Miami Heat this season.

For most of the night, Wizards star John Wall kept pace with Thomas as the two went shot-for-shot.

Wall wound up with 40 points — two shy of his career playoff high — and 13 assists.

“I was playing great defense on him 1-on-1,” said Wall, who answered a question about if he had ever been involved in individual showdown like that with an emphatic “Nah, nope, nope, nope.”

Wall’s point total was tied for the second-most in a Wizards playoff loss (Elvin Hayes in 1974 vs. New York).

“It was just me coming out trying to be aggressive for my team, doing everything I can to help this team win,” he said.

Markieff Morris had 16 points, Marcin Gortat totaled 14 points and 10 rebounds and Bradley Beal also scored 14.

Al Horford added 15 points and 12 rebounds, Avery Bradley and Jae Crowder each had 14 while Terry Rozier was a spark plug off the bench with 12 for Boston.

Kelly Oubre Jr. sank a 3-pointer to make it 117-114 at the 3:55 mark of overtime, only to have Horford make a cutting finger roll 18 seconds later.

Thomas’ floater at 2:48 put Boston up 118-117 and Bradley slammed home a thunderous breakaway dunk at 2:22 after he stripped Wall for the steal.

Thomas’ driving layup gave the Celtics their biggest lead at 122-117 with 1:42 on the clock. Oubre’s dunk brought Washington within three before Thomas essentially sealed it with his three-point play at 1:07.

Horford added a driving hook and Thomas made a pull-up jumper to cap the win.

“It was a hell of a basketball game,” Wizards coach Scott Brooks said. “Two teams played their hearts out. Two great players played well. I thought both teams competed, nothing to be ashamed of.”

Washington went ahead 95-88 with 10:23 remaining in the fourth quarter, but the Celtics tied it at 99 with 7:44 to go and again at 110 with 1:38 left.

Wall hit 1 of 2 free throws with 1:04 on the clock to give Washington a one-point lead, but Thomas hit a jumper on the other end to put Boston up 112-111 with 46.9 ticks left.

Porter drilled a corner 3 with 32.6 seconds left to flip the score again for the Wizards 114-112.

Thomas was fouled by Gortat with 14.4 to go and made both free throws to knot the score.

Wall missed a jumper with 1.9 left and Beal’s desperation fadeaway was off target to force overtime.

The Wizards extended their 67-64 halftime lead with a 14-0 run early in the third quarter, which Wall capped with a three-point play to make it 81-67 with 7:57 to go in the period.

Boston crept within 89-84 by the end of the third.

Once again, the Wizards were the first team to 16 points — only this time the Celtics were not held scoreless. Washington opened Game 1 on a 16-0 run.

The Wizards led 16-8 at the first timeout and expanded their advantage to 42-29 by the end of the first quarter.

NOTES: Boston G Avery Bradley suffered a right hip pointer with 1:11 left in the first half and went to the locker room. He started the second half but again left for treatment in the third quarter before coming back in the fourth. … Washington F Otto Porter Jr. took a head-to-head hit from G Isaiah Thomas and began gushing blood from his nose with 7:47 left in the third. He was helped to the locker room but later returned. … Wizards F Markieff Morris started after leaving the series opener in the second quarter with a left ankle sprain. With Morris in the lineup, Boston started F Amir Johnson over F Gerald Green. … Celtics assistant Walter McCarty offered his support for Baltimore Orioles star Adam Jones, who claimed he was targeted with racial slurs during Tuesday’s game at Fenway Park, while also defending Boston. “You should never cross the lines with that. It’s unfortunate for our city. I think we’ve done so much not to be viewed in that light. … We can’t let those guys speak for the city,” McCarty said, adding that he didn’t have that experience during his playing days. … The Wizards and Celtics meet in Game 3 on Thursday in Washington.