Medical personnel examined Flacco on the sideline, and the Ravens do not believe the injury is serious enough to merit an MRI, sources told Werder.
Flacco, who stayed in the game and orchestrated Baltimore's last-minute go-ahead drive, said the hit caused his knee to "cave in" but that his knee felt "fine" and "strong."
"He fought through that," Ravens coach John Harbaugh said. "Joe Flacco is one tough guy. He's a great player in crunch time."
Flacco downplayed the hit Sunday, even though he still had a slight limp after the game.
"It wasn't really bothering me once the initial hit [happened]," said Flacco, who was 20-of-38 for 222 yards. "I was probably more scared than anything from just what I felt, and also just trying to get a couple of yards out of it."
Flacco, who has not missed a game in his six-year NFL career, told WBAL radio in Baltimore that he would be fine playing with a knee brace.
The Ravens (8-6), who are battling for the AFC's second wild card, host the New England Patriots (10-4) on Sunday.
ESPN.com Ravens reporter Jamison Hensley contributed to this report.