Campbell was carted off with a dislocated left kneecap in the second quarter. NFL Network's Adam Schefter reports Campbell is expected to be out one month. Campbell's left leg buckled when he was hit by defensive end Mark Anderson, one of three Bears defenders who converged on Campbell as he completed a pass.
Campbell was replaced by Todd Collins, who threw his first pass in a regular-season game since 2004 and later completed his first touchdown pass since 2002.
Collins completed 15 of 20 passes for 224 yards and two touchdowns, his fifth career two touchdown game and first since 1997.
Minutes before he was carted off, Campbell was hit on his throwing elbow by defensive back Brandon McGowan near the sideline at end of a 2-yard gain on a quarterback scramble. Campbell missed only one play, and the knee injury occurred on the third play of the Redskins' next drive.
Campbell finished 10-for-16 for 100 yards.
Grossman left in the first quarter with a knee injury and did not return. His left leg twisted awkwardly when he was driven into the ground by defensive lineman Cornelius Griffin.
The injury happened on Chicago's second possession, slightly more than 4 minutes into the game.
Grossman was 2-for-6 for 14 yards. He was replaced by Brian Griese, who completed 27 of 45 passes for 295 yards with a touchdown and two interceptions.
Redskins right guard Randy Thomas, who had been out since Week 2 with a torn left triceps, returned to the starting lineup Thursday, but he left in the first half with an elbow injury.
Two plays before Campbell left for good, Redskins tight end Chris Cooley was injured. He later limped to the locker room but returned for the start of the second half. He finished with five receptions for 93 yards.
Copyright 2007 by The Associated Press.