Coach Mike Shanahan made the announcement Monday, just one day after the Redskins' quarterback was forced out of his team's first-round playoff loss due to the injury.
In the fourth quarter of Sunday's 24-14 loss to the Seattle Seahawks, Griffin could not handle a bad snap and his right knee, which he previously injured during the Redskins' second possession of the game, buckled under him while he scrambled for the loose ball.
Griffin remained on the ground for several minutes before getting up on his own power and walking off the field. He did not return.
According to Shanahan, Griffin is going for more exams because there was an issue distinguishing between old and new injuries in a knee that's had previous ACL and LCL injuries.
Shanahan said that "everything right now is total speculation."
Griffin originally injured his right knee in a Week 15 win over the Baltimore Ravens and sat out in Week 16. Griffin returned to action and guided the Redskins to a 28-18 win over the Dallas Cowboys and the NFC East crown in the regular-season finale.
