Is There A Crack In The Thigh Muscle?

My ten year old daughter has scoliosis diagnosed by her pediatrician only last year. She said next appointment she will measure it again and then decide if we need to see a professional. I see that she either has one leg longer or hip higher than the other. She is a soccer player competitive and practices about 6 hours a week. Lately she has noticed than when she opens her legs her thigh muscle cracks. I can here it. It s more like a popping noise. Any clue if all this is related ? Thank you