Possible FSHD 12 year old

Looking for help:

My son (12 years old) just 7 weeks ago was the most athletic kid in his class; no physical issues at all. I know I’m his dad but he really is a super athlete.

During a basketball game he falls and suffers a pars defect at L5. Begins limping for 3 weeks. Loses his limp and walks normal. We then begin to notice his whole right side is weak. He can barely activate his quadriceps muscle. Very Little bicep strength and no tricep strength. Also has foot drop.

Left side is all normal. I think good core strength. He can hold a plank for 1 minute.

Went to neurologist. 112 CK levels, normal alt and ast levels. Normal thyroid stimulating hormone level.

No facial weaknesses, he can whistle, swallow.

No family history.
EMG and NCV results were normal but don’t match muscle weakness.

Love to hear your thoughts.