GLENDALE, Ariz. -- Detroit Lions running back Reggie Bush will have an MRI on his left knee to determine what might have happened to it after he was injured in a 25-21 loss to Arizona on Sunday.

Bush injured the knee when it collided with the helmet of Arizona safety Tony Jefferson during his 26-yard run after the catch in the second quarter. As he was going down after the hit, he clutched the knee.

"Yeah," Bush said. "It hurt."

Bush was cleared to return to the game later in the quarter and played in the third quarter as well. But after he fumbled the ball in the third quarter, he left the game and did not return.

He finished with nine carries for 25 yards and three receptions for 44 yards.

"I was able to go back in the game, but I wasn't myself," Bush said. "I probably shouldn't have gone back in. But I went back in and tried to give it a shot. Felt like I could still go, but I wasn't myself.

"We'll see what happens this week, I'm not sure. I don't think it's anything serious."

This is the second straight week Bush has been banged up during a game. He dislocated his thumb and also pulled his groin last week in a win against Minnesota.

Bush said he plans on rehabbing most of this week in preparation of attempting to be ready for Detroit's next game -- Sunday at Washington.

"I'm sure we'll go through every fine-tooth comb on everything," Detroit coach Jim Schwartz said. "He's an important player to us. We'll certainly do every test that we can."