Hi,
I just wanted to agree with everyone else who said to have regular checkups say every 6 months. Unfortunately, I also do not believe there is a "cure" unless all symptoms disappeared in the first 6-8 weeks.
I have come to realise that it is a life long injury. My daughter is almost 5 and has very good function but unfortunately she does regress a little every time she has a growth spurt. We need to do more therapy (stretches and exercises) during these periods to regain function.
The function she looses is only at the end range and sometimes you can miss this as a parent (other times you are acutely aware of it). A physio or O/T will keep track of everything and pick these up though.
In the last year her shoulder winging and dropping has become more prominant. She has also started to complain of some pain in the elbow.
Every child is different but for piece of mind I would see a therapist on a regular basis. An occupational therapist may be more appropriate than a physio for his current age and if there is no muscle tightness.
Best of luck,
Kelly.