Pennington, reinstalled as the Dolphins' starting quarterback last week, was hurt on his first play in Sunday's 29-17 victory over the Tennessee Titans at Sun Life Stadium.
He was hit while throwing an incompletion on the first play, completed a pass on the next play, then left the game.
Pennington lost his starting job to Chad Henne in Week 3 of last season, when the two-time NFL Comeback Player of the Year suffered a season-ending right shoulder injury.
Pennington was given his first start Sunday because the Dolphins' offense had been ineffective under Henne.
Henne replaced Pennington and performed well, completing 19 of 28 passes for 240 yards and a touchdown with one interception before injuring his left knee in the third quarter.
Henne left Sun Life Stadium on crutches. There has been no word on the extent of his injury pending the results of an MRI.
With Pennington and Henne hurt, third-stringer Tyler Thigpen came off the bench Sunday and led the Dolphins to the victory.
Tim Graham covers the AFC East for ESPN.com. Information from The Associated Press was used in this report.
source:http://sports.espn.go.com/nfl/news/story?id=5809215&campaign=rss&source=NFLHeadlines