Hello, thank you for your question. Since the results of spine xray and MRI are normal , the next more common medical condition that may cause your problem is Diabetes , by damaging the peripherical nerves of the foot. So I would check you blood sugar and all other tests for Diabetes. Other rare disease might be multiple mieloma or bilateral piriformis syndrome , but that the gives this simptoms when sitting with leg crossing nore than walking. i hope this answer will help you.