The airing of grievances is a Festivus tradition.

The Knicks’ playoff run began with a Festivus of their own.

Head coach Mike Brown met individually with each of his five starters — Jalen Brunson, Karl-Anthony Towns, OG Anunoby, Mikal Bridges and Josh Hart — and then all of them collectively for them to air their grievances before the Knicks entered the postseason, according to SNY.

The meetings were conducted for the players to get lingering issues off their chest, and Brunson’s dad Rick, one of the Knicks’ assistant coaches, told SNY that those meetings “were pivotal to New York’s playoff success.”

After the Knicks fell behind 2-1 in the first round against the Hawks, they reeled off 13 straight victories as part of a surreal run to their first NBA championship in 53 years, culminating with Saturday’s 94-90 win over the Spurs in Game 5 to win the NBA Finals 4-1.

Jalen Brunson was unanimously voted NBA Finals MVP after carrying the Knicks in the finale with 45 points on 14-for-27 shooting while going 13-for-15 from the free-throw line.

Brown, the 56-year-old in his first season with the club, set the tone from the outset by having everyone put their commitment in writing.

“The buy in. It was a contract that I had everybody sign opening dinner night and I still have it framed,” Brown told MSG Saturday night. “Everybody’s signature from Mr. Dolan to Leon Rose, all the coaches, all the players, all the staff that was there that night signed it and basically it was about committing to sacrifice, having a competitive spirit, being connected, believing in each other in the process while holding everybody accountable — even myself. I’m not above the law, I’ve gotta be held accountable too.

“I told everybody that night, if you’re not gonna abide by this, I’d have more respect for you to not sign it than to sign it and BS your way through the night and BS your way through this and everybody bought in from Day 1. And that speaks volumes to all of these guys as individuals and especially the leadership on this team, starting with Jalen Brunson.”