I don't think Dirk has any history of knee surgery. An athlete's initial reaction usually tells the true story.
Remember Pierce in the 2008 Finals? Lol. He looked like he got his leg blown off and was dropping treys just a few minutes later.
Athletes sometimes overreact out of nervousness. They know their bodies extremely well, better than you or I. An athlete that has a history is even more likely to react in that manner.
Keep in mind I am saying this as a complete optimist that this isn't going to severely alter our title chances. I'm trying to stay glass-half-full right now because this is extremely unsettling.
I could care less about this game tonight in all honesty, and I haven't said that since the 2006-07 season.