He will undergo an MRI on Monday morning.
Melton left the game with 12:58 to play when he fell awkwardly while trying to make a move as he was engaged with a Pittsburgh offensive player. The team announced minutes later that Melton would be out for the remainder of the game with the knee injury.
Prior to suffering the injury, Melton recovered a Felix Jones fumble caused by safety Major Wright that led to a Robbie Gould 32-yard field goal with 10:58 remaining in the third quarter. The play gave the Bears a 27-10 lead that was trimmed to 27-23 with 10:38 left.
The club's franchise player, Melton suffered a concussion during the preseason opener against the Carolina Panthers that slowed him through the first two games of the season. Going in to Sunday's game, Melton hadn't yet contributed a sack after coming off a 2012 campaign in which he contributed six sacks.
Melton has posted 13 sacks since 2011, which ranks as No. 2 in the NFL among defensive tackles during that span.