his inability to bear weight on this one leg does not necessarily mean the problem is in the hip. it could be in the leg knee ankle or foot. the reason many x-rays are normal is that the problem may not even be due to a bone injury but rather muscle or tendon (like a sprain). these things do not show up on an x-ray. i even had a non-walking toddler with a thorn in his foot that no one noticed. toddlers can be wild and crazy and injury themselves in a zillion different ways without you even knowing it. the fact that he has not improved in a week is concerning so i would suggest that you take him to see his regular doctor. he may need to complete the entire leg x-rays series if the doctor feels it is justified. one quick story: a patient of mine same age woke up from a nap and would not bear weight. several (negative) x-rays negative exams and watchful waiting for three days did not seem him improve. i coerced a orthopedic friend to work him into his busy and over-booked schedule so he agreed to see him over lunch. this little guy who had been carried for the last three days ran through his waiting room jumped up on some chairs and acted like he did not have a care in the world. to this day his parents and myself have no idea why he did not want to walk. perhaps he enjoyed being carried for a while?
my 15mo son walks and plays normally then will suddenly have an issue with leg. won't put any weight on it. i took him to er and had his hips xrayed. they said there were no problems with the bones. this has been going on for a lil over a week. he isn't running fever or have any other illness. he isn't allergic to anything.