What's Up With Pierce's Knee?

Reading about Walker's knees and thinking about whether the Celtics would extend Powe this summer with his knee situation, I came to a larger quandary: Pierce's "sprained" knee. I mean, have you heard anything about this? Because I haven't. Paul had an apparently horrific knee injury in Game 1, but battled back and won MVP. By that point we had obviously figured his injury wasn't nearly as bad as [link]