The Celtics vs. Knicks action wasn’t just limited to inside TD Garden on Wednesday night … some of their fans got into a wild brawl outside the venue as well — and a good portion of the scrap was captured on video.

Check it out … just after New York stunned Boston with another come-from-behind road win, several people clad in blue and orange mixed it up with some C’s backers.

A man in a Paul Pierce jersey appeared to get the better of one Knicks fan — bloodying him with a flurry of punches. Nearby, a Jalen Brunson supporter clearly had his hands full with his rival too.

Cops raced to the scene and appeared to break things up before they turned even more violent. It seemed at least one of the combatants was placed into handcuffs — though it’s unclear if any formal arrests were made. We’ve reached out to Boston police for more info, but have yet to hear back.

It was hardly the only instance of wild fan behavior following NY’s 91-90 victory … inside the arena, a bevy of Knicks fans were spotted chanting and refusing to leave their seats despite an usher’s consistent pleas.

Meanwhile, as a Celtics postgame show was going on in a concourse at the stadium … several New York fans could be heard screaming obscenities as the show’s hosts tried to break down the loss.