CSN Chicago is reporting a possible torn MCL for Cutler:
http://www.csnchicago.com/pages/word_on_the_streetQuote:
Cutler to undergo MRI Monday
It's no secret around Chicago that Jay Cutler left Sunday's NFC Championship game with a right knee injury, but there have been questions surrounding the situation as to the extent of the injury. On Monday, some of those questions will be answered as the Bears' franchise QB is scheduled to undergo an MRI on his injured left knee.
Cutler claims the Bears coaching staff wouldn't let him go back out on the field after playing just one series in the second half in the loss to the Packers. Teammates Olin Kreutz and Brian Urlacher mentioned there may possibly be a torn MCL. (Chicago Tribune)
If that's true, then the Bears were correct in keeping him out today.