I Have A 13 Year Old With Osteochondritis Dissecans On

I have a 13 year old with Osteochondritis Dissecans on both knees, his unable to walk due to pain and unable to stretch his leg. He can run, jump or play any sports. The Orthopedic's recomm. no surgery until his 15 year of age his had it seen he was 10 years old. Not sure if steam cells injections will work for a child. What can I do to help him.