Matt Forte left with a knee injury in the second half of Sunday's 23-20 loss to the Minnesota Vikings.
Forte, 29, walked to the locker room in Chicago under his own power and did not return. After the game, Bears coach John Fox told reporters he didn't know the severity of the injury.
The Bears' running back suffered a big hit in the open field by Minnesota Vikings safety Harrison Smith early in the third quarter.
Forte, the Bears workhorse, earned 41 yards on 10 carries and four receptions for 28 yards before exiting.
Chicago receiver Eddie Royal also exited the game with a knee injury and was ruled out.
