Fractured Tibia-Fibula

My son fractured his tib-fib 10/02 in a football game.
It was a clean fracture with very little displacement of the tib and approx. 50% overlap of the fib.
Since he was being recruited for Division I football, we elected no pins so no surgery would be required around the knee area.
He was in a plaster cast and used a bone stimulator. Bones appeared to heal nicely, but now he is practicing with the college team and having ALOT of “muscle” pain (not bone pain) in the area of the break.
He is very discouraged because it has been almost one year and he still can’t sprint, cut or plant during drills without significant pain.
The leg has been re-xrayed several times and everything looks ok.
What could be causing this extreme pain?
What kind of treatment might help? He needs some encouragement.
Thank you.