Bengals right tackle Trent Brown was blocking Commanders defensive lineman Dorance Armstrong when Brown’s knee gave out.
Brown stayed on the ground, grabbing at his right knee, before requiring a cart to get off the field.
The Bengals offensive linemen helped Brown onto the cart, wishing him well before he departed for the X-ray room with 6:25 remaining until halftime.
Rookie Amarius Mims, who had his first NFL snap six plays earlier on a field goal drive, replaces Brown.
The Bengals already have ruled out Brown, a sign that his injury is as serious as it looked.
The Bengals trail the Commanders 14-10.
