It is necessary for you to take your
dog to the vet and get this explored, probably through an x-ray. In the meantime, keep her as calm as possible and don't take her for walks and definitely don't let her jump up or climb stairs.
If the problem is caused through trauma rather than disease, then rest for a few days may resolve the problem - but it is worth getting a vet to check it out properly, so you get a propper diagnosis.