Flacco was hit on his knee by the helmet of Detroit Lions linebacker DeAndre Levy in the fourth quarter of the Ravens 18-16 win on Monday.
Flacco wore a brace at practice on Wednesday and will continue to wear it for Sunday's game. He has started 94 straight games since entering the league in 2008.
"It was uncomfortable a little bit," Flacco said. "If it protects it, it's all good for me. It's getting better, that's a good sign I think."
Flacco, who was 20-38 for 222 yards against the Lions, said he had a scary feeling after being hit on his knee.
"I felt something obviously when I got hit down there," Flacco said. "And then Ray came over and wanted me to get up but he didn't really help me. I wasn't really ready to get up yet because I didn't want to get up and test it out and have myself collapse to the ground and look like a hit. I've never really had a severe knee injury, so you don't know what is what. So when you feel something, you definitely get a little bit scared."