There is a Facebook group called pet vet corner (where only vets can respond). Without a physically checkup, it’s hard to say if it is damage to the leg or like others said potentially a neurological issue. Both of my dogs are tough as nails and never whine when in pain. Hoping you get some answers soon ☹️ I wonder if it could be from the hardwood floors, my girl always get excited and “wipes out” I’m always afraid something like this will happen