Jalen Brunson scored 39 points as the New York Knicks beat the Boston Celtics 121-113 to leave the reigning NBA champions on the brink of elimination from the play-offs.

The Knicks stormed back from 14 points down in the third quarter to go 3-1 up in the best-of-seven Eastern Conference semi-final and are in sight of the finals for the first time since 2000.

The Celtics also lost forward Jayson Tatum, who scored 42 points before being carried off in the fourth quarter with what coach Joe Mazzulla described as a “lower body injury”.

The six-time All Star, who was later seen being taken to the Madison Square Garden locker room in a wheelchair, will have a scan on Tuesday to assess the damage.

“He’ll get the MRI and we’ll see what it is,” said Mazzulla.

“Obviously you’re always concerned about someone’s health. It’s two-fold, we’re concerned about his health and where’s he’s at. And then we’re concerned what we’ve got to do better in game five.”

The Knicks can clinch the series with a win in Boston on Thursday (00:00 BST).

Boston, who won game three on Saturday, started strongly with Tatum and Payton Pritchard leading the charge.

A Derrick White three-pointer gave the Celtics their biggest lead of the night early in the third quarter (72-58) but from then on the Knicks took over, taking an 88-85 lead into the final quarter.

Brunson controlled matters and when OG Anunoby grabbed a steal off Tatum in the incident that left the Celtics star writhing in pain before making a dunk, the Knicks were 118-106 ahead.

“I was just in a flow and doing whatever. I wasn’t really trying to take over. It was just ‘whatever we’ve gotta do’,” Brunson said.

“We didn’t quit, kept fighting. And that’s what’s most important. Whenever you get in a hole you can’t quit.”