i blew out my right knee twice while playing college football as well as a few scope jobs on my left knee. There will be a few exrea stops for him at the medical office. You will need to have x=rays done and be seen by the ortho at metrotech to ensure the injuries are no longer a problem. You will also need to have access to ALL of the records from the surgeries and provide them to the investigators. This was a pain in the ass but i had all of my work done by the same doctor so it was all a matter of getting in touch with his office and having his people send over everything to metrotech. The investigator will tell you everything you need to get and whom to send it to when the time comes. Legally, the injuries cannot prevent your son from getting on the job unless of course it is still a problem. just as long as he completes and passes all of the physical aspects he should be good to go. There was a story in upstate NY where a vereran who was an amputee below the knee took the FF test, passed the physicals and everything at the top of the list, when they tried to deny him the job the courts overruled citing disability discrimination. Short Answer, if your son can do the job he is good to go.