Kosier said he injured it in the third quarter and tried to play through it, but the pain was too great. Kosier limped off the field with 7:49 to play. He will undergo further evaluations on Monday.
Meanwhile, cornerback Mike Jenkins re-injured his right shoulder and was given limited snaps in the second half because of the injury. He's been bothered by the shoulder the last few weeks and isn't sure if he will need surgery.
"I hope not," Jenkins said. "I've never had surgery before and I'm not trying to have my first one. Hopefully it's a process I can get through with time letting it heal."
Jenkins said he will undergo an exam on Monday.
Cornerback Terence Newman left the game briefly after getting hit in the head while trailing a play. Newman was fine.
Calvin Watkins covers the Cowboys for ESPNDallas.com.