How did Adam Dunn hurt his knee?

[texasdave]

It has been widely reported that AD's knee has been hurting him not only this year, but in 2006 as well. My question is simply does anyone know how he hurt his knee in the first place? Is this a case of cleaning up some wear and tear? Is it unusual for a 26 year old player (since it hurt him in 2006) to need to have his knee cleaned up? Does this bode well long-term? Once the procedure is done is that the end of it? Is his other knee next? It stands to reason that if one knee has shown that much wear and tear that the other quite possibly isn't far behind. I think these are important questions that need to be answered if the club is pondering a long-term extension with Dunn. So, once again, does anyone have the scoop on Adam's injury?

[GoReds33]

When you weight 250 pounds, you can hurt yourself pretty easily. It's probably just wear and tear.