Does anyone actually know why his knees are dodgy? Too many people are assuming it's just a standard recurring knee-injury, it's not. After breaking his leg a surgeon fecked up an operation and one of the pins somehow went into/around his knee as it was being removed. It can be painful but it's not the normal recurring ligament or tendon strains or permanent cartilage damage, the problem is it's supposed a degenerative condition. I'm no knee-surgeon though so this could all be wrong.
I could imagine him playing for a few years without any trouble - physically he's not going downhill yet as a 26 year-old which should keep him fit for a good while.