I'm sure Vince may have known about the injury, but obviously not the extent of it. Keep in mind, Edge himself has spoken after the fact on more then one occasion on how he didn't know of the extent of the injury. So, using that logic, how could have Vince McMahon? It just doesn't make sense to me on several levels that Vince could have known.
Edge did speak of how he was beginning to feel symptoms before Wrestlemania, so it's perfectly reasonable to believe that Vince knew something. The man is as hands-on as it gets, so it would surprise me that if Edge was dealing with physical issues, Vince didn't know. Say what you will about Vince, but he wouldn't have let Edge go out there and compete if he knew the injury was as serious as it was. That's risking a lawsuit, and also alienating another of the greatest wrestlers of all time. That means losing Edge forever. This means no ambassador work, no special appearances, no future endorsement deals, and no Edge in non-wrestling role in the future, which he's stated his desire to fo. In short, it could have cost Vince alot of money had he let Edge go out there, knowing how badly he was injured.
Further, Edge was proven time and again to be one of the smartest wrestlers in WWE, perhaps in history. Do you think he, as still a young man, would risk the ability to enjoy the rest of his life over one match? Don't think so. What would Vince do, fire him if he refused to wrestle? I say this in jest, because Edge was retiring anyways. I believe that what Edge knew, Vince knew, and it obviously wasn't believed to be serious enough to keep him from continuing to wrestle.
Instead of speculating of what Vince knew and didn't know, we should be thankful we got one more match from Edge, and that he walked out of it under his own power. Sure beats a stretcher, doesn't it?