Flacco went to the ground after the helmet of Detroit Lions linebacker DeAndre Levy nailed him just below the knee. The hit, which came with 8:52 left in the game, caused Flacco's knee to "cave in," according to the quarterback.
But, after Flacco gingerly got back up, he played the rest of the game.
"It feels fine," Flacco said after the Ravens' 18-16 win over the Lions. "It feels strong."
The Ravens were concerned enough that backup Tyrod Taylor began to warm up on the side as Flacco stretched out his leg. Flacco got the left knee taped up and he went back on the field after the Lions took a 16-15 lead with 2:21 left in the game.
On the Ravens' final drive, Flacco threw primarily off his back foot, completing 2 of 5 passes for 27 yards, which was enough to get the Ravens into range for the winning 61-yard field goal.
"He fought through that," coach John Harbaugh said. "Joe Flacco is one tough guy. He’s a great player in crunch time."
Flacco downplayed the hit, even though he still had a slight limp walking to the postgame podium.
"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 never missed a game in his six-year NFL career, was asked whether he was going to get additional testing on the knee. The Ravens play host to the New England Patriots in six days.
"I have no idea," Flacco said. "I have talk to the trainers and see what the protocol is."