Munchak said Britt, the AFC's leading receiver this season with 271 yards on 18 grabs, had torn the ACL and MCL ligaments in his right knee and will undergo surgery.
Britt sustained the injury while catching a pass along the right sideline in Sunday's 17-14 win over the Denver Broncos. He appeared to twist his knee as he cut upfield, fumbling the ball.
The receiver has had seven run-ins with the law since 2009.
He pleaded not guilty in July in New Jersey to three disorderly persons offenses stemming from a June incident in Hoboken when he was arrested by plainclothes narcotics officers who claimed Britt crushed a marijuana cigar in his hands to conceal it from investigators.
He pleaded guilty to speeding in June after felony charges were dropped following a police chase in his hometown of Bayonne, N.J.