From what I understand the injury is more around the sensitivity it causes to the shoulder rather than any risk of a deterioration to the area. The problem is if you're playing a physical game where every contest you go into you're worried about getting hurt that really does impact how you play the game. The pain can also become so over-whelming you can't continue, which is what has happened to Houston several times already, but this doesn't mean he's damaged his shoulder further. This is not to say he hasn't damaged his shoulder because he has, but its the sensitization of the injury that is the current issue. Generally over time this should get better if he doesn't damage the shoulder further.
It's really a pain management issue from what I understand: there's a whole segment of medical science that covers this, under the umbrella area of medicine called the bio-psycho-social theory of medicine. There's actually an Australian expert who is one of the very world leaders in this area: Professor Lorimer Mosley, he has some vids up on youtube aimed at a lay audience about it and they're worth the watch. His story about being a hitchhiker and getting picked up by a driver missing a limb and also his experience getting bitten by one of the world's most venomous snakes really illustrate his points. Worth the listen if this area piques anyone's interest.
Edit: Mosley has actually advised the Port Adelaide football club previously, as he worked out of the University of South Australia at some stage.
