According to a report on Comcast SportsNet New England, Gronkowski has a broken forearm.
"He left the game with an arm injury," Patriots spokesman Stacey James said about 2½ hours after the game. "There was no update to that."
On Monday, Boston.com reported that Gronkowski will undergo surgery Monday morning.
Gronkowski, 23, had seven catches for 137 yards on Sunday, including touchdowns of 4 and 24 yards in the game. He was reportedly injured while blocking for an extra point on New England's eighth touchdown.
The happy-go-lucky Gronkowski had 10 touchdown catches as a rookie and then set an NFL record for tight ends with 17 touchdowns last year, when he caught 90 passes for 1,327 yards. But he sprained his left ankle in the AFC title game and was a nonfactor in the Super Bowl, which New England lost 21-17 to the New York Giants.
The Patriots had been without Aaron Hernandez, their other first-string tight end, for the last three games — and a total of six this season — after he sprained his right ankle in Week 2. He has just 17 catches for 143 yards and two touchdowns in four games.
Hernandez went from being listed as "out" in the injury report to "questionable" after the Nov. 4 bye week and remained that way for each of the last three games. He had limited participation in practice in each of the last three weeks; the team has not given a timetable for his return.
The Patriots next play on Thanksgiving night against the New York Jets.
The Patriots made no announcement about Gronkowski's injury when he headed for the locker room with about 4 minutes left in Sunday's game. Several hours after the game, James said he had no information; inquiries to the NFL media relations department were referred back to the Patriots, who then said Gronkowski had an arm injury.
According to the NFL's media policy, "Team personnel are responsible for reporting in-game injury information factually and accurately as soon as possible for the benefit of the network television audience and the other media covering our games."
"Clubs must ensure that all medical information issued to the media is credible, responsible, and specific in terms that are meaningful to teams, media, and fans," says the policy, which goes on to remind teams that "the injury reporting policy relates directly to the integrity of the game."
Copyright 2012 The Associated Press.