Aminos are mostly part of the gym rat world.
First thing I would is get a bunch of pineapple, kiwi, and/or papaya.
Fruit will help healing, but those fruits have enzymes that help digest food.
Very good for recovery.
Second thing is a bunch of walking. We are talking about the tough stuff,
tendons and such. They don't get a lot of blood flow, and the walking will help
Third thing is to cut back on the things that cause inflammation. Sugar, booze,
too much food, or a lack of alkaline foods. Kids tend to lack enthusiasm for alkaline foods.
Try to sneak some in.
Is he in PT and stretching? If not, find some hip stretches (check with the Doc first)
and after his walks, have him stretch.
I have a suspicion he has a weakness in the hip area. A lot of Americans do...
You need a good PT to find it.
Sadly a lot of them are not that good. If you look into it yourself, find out how to check
the pelvic floor, hip muscles and low back.