My daughter suffers from unexplained pain in quadriceps, what can it be?

I have an 11 year old girl, she suffers from burning and stinging pain and “clicking” in quadriceps. She has been suffering from this pain since she was little. It usually occurs after physical sports activities. She had had x rays, MRI and blood tests but nothing has been found. Please help.

Age: 11
Female
Medications: None

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