He isn't a lameness specialist, though. Maybe I will try to find one to come and look at her.
Then that would be my next step, when you are able. Find a good
equine lameness vet to do a second opinion.
The x-rays were done on each leg and her back. Nothing was found. Surely if the fence injury caused damage to the bone, than there would be excess bone at the place of injury?
What type of x-ray machine does your vet have? Digital? Or the old fashioned screens?
My vet, my mom, my trainer, and even me at times, messed with that leg to see if we could find a sore spot. We stretched and bent it in every direction. We lifted the other foot so she would have to stand with more weight on her right, and she didn't really care. That's why we went for the ultrasound for cysts, we thought surely it isn't her leg. It must be something internal.
Did your vet do flexion testing? Its one thing to flex on a leg, but it's another to then watch the horse immediately trot off after the "stress" was applied. That's where a good equine vet comes in, to find the little subtle things where a horse might look "off". Takes a very trained eye to do so. I've have a lot of lameness problems with my horse Red, and I don't always see what they see .... but I'm not a lameness vet with years of experience!
Which is why a second opinion wouldn't hurt. Not trying to say your current vet has done a bad job, but if he isn't a lameness specialist, he might not know exactly what to look for or how to recognize it.