Hi, I am Dr Suresh K Yadav MD (paediatrics), I had gone through your question and understand your concerns, If other things including examination are normal it is most likely muscular pain related to either cramps or injury. If it is occurring frequently vitamin D deficiency may be a contributory factor . Other deficiencies like calcium ,iron and vitamin needs to be ruled out. But if a single event and examination normal , you need not worry , it do occur with growing . Hope this answers your question. If you have additional questions or follow up questions then please do not hesitate in writing to us. I will be happy to answer your questions Take care.