Did he do his PCL playing in the ruck? It's the typical injury ruckmen have suffered. I hope in the quest to try to help him find form, the team hasn't increased his risk of this injury. North does the same playing Larkey as a relief ruckman - I hate it when this happens.
Not sure, but I did remember seeing him fall awkwardly in a marking contest early so I reckon that was when he did it.
We threw him into the ruck after half time when we subbed Campbell off.