HOUSTON (AP) -- Houston Texans star J.J. Watt injured his left knee in the first quarter against the Kansas City Chiefs, and was placed in an ambulance and taken to a hospital.

The defensive end fell to the ground while being blocked midway through the quarter Sunday night.

Watt remained on his hands and knees for a couple of minutes while trainers checked on him. They flipped him onto his back and were looking at his left leg. He was then helped to his feet and looked to be in a lot of pain and didn't appear to be able to put any weight on the leg as he was helped off the field by two Texans officials.

The three-time Defensive Player of the Year returned this season after missing the last 13 games of last season after his second back surgery.

He remained on the sideline under a tent for a few minutes before being taken to the locker room on a cart.

About 30 minutes later, television footage showed Watt walking on crutches to an ambulance before sitting on a stretcher, being moved into the ambulance and taken away.