Griffin's first notable injury in the pros was a concussion early this season, which led the quarterback to learn to protect his body better while running the ball.
But last month, at the end of a 13-yard scramble, he sprained the LCL when he was hit by Baltimore Ravens defensive tackle Haloti Ngata. Griffin missed one game and returned to play in three more while wearing a bulky knee brace, his mobility clearly hindered.
On Sunday, Griffin hurt the knee again as he fell awkwardly while throwing a pass late in the first quarter against the Seahawks. He was mostly ineffective the rest of the game, completing only four passes after that drive.
Griffin finally departed with 6:19 to play in the game, after the knee buckled while he was trying to field a bad shotgun snap.
The No. 2 overall pick in last year's draft, Griffin was one of several rookie quarterbacks to make an instant impact on the NFL this season. He set the league record for best season passer rating by a rookie QB and led the Redskins to their first NFC East title in 13 years.
Griffin's knee has kept the nation's capital on tenterhooks all week. He was hurt Sunday. Then Shanahan announced Monday that a second opinion was needed.
Then on Tuesday came word that surgery would be taking place. Wednesday was the actual surgery. While it was taking place, District of Columbia Mayor Vincent Gray said he will invite Griffin to watch President Barack Obama's inaugural parade on a reviewing stand outside the district government building later this month.
"I'd love to have him come, but ... he obviously may be unable. His mobility may be impaired somewhat at that point," Gray said. "My focus right now is on having him successfully get through the surgery."
AP Sports Writer Rachel Cohen in New York and Associated Press writer Ben Nuckols in Washington contributed to this report.
Follow Joseph White on Twitter: http://twitter.com/JGWhiteAP
Online: http://pro32.ap.org/poll and http://twitter.com/AP_NFL