This is a silly thread!
What evidence is there to even ask the question "has killers knee popped already" ?
The answer is none.
If you read the page on the os Killer says that his knee is a bit sore, but that he will be ok in the pool, ok on the bike and hopes to resume training in a few days. No hint of any serious problem at all.
Forget any medical explanation - it is surely obvious that with what he has been through there is likely to be a reaction whenever he trains and/or plays. The hope is that he and the club manage it corretly and that he can play most of the league games.