My Grand Daughter Is Eight Years Old. She Has Been

my grand daughter is eight years old. She has been limping lately and at night has leg pains in her right leg. My husband noticed today when she would go up the steps on the porch that she would do this one leg at a time still favoring her leg. In the sunshine we could see that her right leg was more purplish in color than her left leg. My son seems to think it is growing pains but we are concerned that it is more serious than that