That sucks for JP, and the Oilers really.
Wish something would have been done before he came over. His career could already be over at this point. The kid owed it to himself and the team he was going to be playing for, to be in the best possible condition to play hockey.
I wonder if it was just something that flared up occasionally, and he didn't think it was serious because it would go away after a while off skates having only played 50 games with limited minutes (+ international tournaments) in his draft season which was the most hockey he'd played in a year by the looks of it.
Now take that to the grind of the NHL and AHL plus likely more training heavy off seasons, and the pain may have become regular enough for him to start complaining about it rather than ignoring it.
Hopefully it's something that can just be fixed, and he can play without the pain, but being a "body structure" issue makes me think it's something that's going to take a while to adjust to being better.