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And now we know why Dr. James Andrews is pumping the brakes regarding the presumption that Robert Griffin III will become Adrian Peterson II.

Per a league source, there is much greater concern regarding Griffin’s knee than anyone connected to the Redskins or Griffin has publicly conceded.

Yes, he tore his LCL and his ACL. Yes, it won’t be easy to rehab both ligaments at the same time. Yes, they had to invade his healthy knee for a patellar tendon graft. And, yes, Griffin suffered a partial tear of his meniscus when tearing the ACL, a common consequence when the ACL is damaged.

All of those pieces of information have made their way to the media. But the entire result is a stew of concerns that has created a far more negative vibe in and around the Griffin camp than the pronouncements of optimism and quasi-guarantees that he’ll be good as new by September 2013.

Apart from the fact that there’s no way to know how the ACL will rehab, the biggest concern, as the source explained it, is the damage to Griffin’s cartilage. With the ACL in the right knee now torn twice in less than four years, Griffin has lost enough cartilage in his knee to raise concerns about how much remains and how long it will last. Eventually, Griffin could be dealing with bone-on-bone contact, and the chronic pain that goes along with it.

And he’s still only 22.

The first ACL tear was long forgotten during Griffin’s stellar rookie season. In fact, most fans didn’t even know about it, because Griffin was hardly a nationally-known name at the time the injury happened. But there was a real physical risk when the Redskins gave up three first-round picks and a second-round pick to get Griffin, and less than a year after making the trade the team now has to wonder whether Griffin ever will be the same — and if he is how long that will possibly last.