Thank you for your query.
Do not panic.
Your child definitely has a problem.
If the pain is in the same area and it is not getting relieved get another good quality MRI
of the same region.
The type of pain complained denotes a cartilage
tear of ligament tear.
This can be confirmed by arthroscopy
If you have any further queries you are free to consult me.Hope this answers your query.Wishing your child a speedy recovery.Have a nice day.