If your teen is still young, it could be that he has the juvenile version of osteochondritis dissecans. With this condition, a part of the bone becomes detached from a joint and the blood supply can’t reach where it has been detached. For children, the treatment is immobility or rest, depending on the joint affected. By minimizing his sports, he is resting the leg, allowing the joint to heal.
Your son’s doctor will likely have taken x-rays, perhaps even magnetic resonance imaging (MRI). By repeating these tests, the doctor will be able to tell if the lesion is healing.
Unless your son is in severe pain, there isn’t any other treatment option available for OD. Surgery is only considered if the pain is severe or if traditional, conservative treatment does not help.