If I could weigh in on the arthritis -
Just to put some context on what I know, I am in my final year of studying physical therapy. I am not close to the situation or know the extent but typically arthritis is going to be more about pain management throughout his career. Seeing as he will be getting the best medical attention and physical therapy that money can buy on a regular basis, I would not worry at all about Allen missing serious time because of it.
He may require some a few cleanup surgeries in the off-seasons to come but I would not be concerned about that.