My friend imported a huge 18.2 just turned 6 year old. He came with xrays and she got more done when he arrived. None on the neck though.
She had a host of problems with him initially. Some were similar to Blob's horse with the stopping, raising the tail, trying to poop, etc. She took him to the clinic and he had bad ulcers in upper and lower GI. Treated with various drugs, etc.
My friend tends to notice every little quirk in a horse. She notices he walks funny on the left hind, but it isn't seen on trot and canter.
She decides to take him to the clinic (2 miles from me). He is looked at there by a good vet/surgeon. They diagnose the problem with the leg. This I can't explain but apparently there is some tendon/ligament that is only affected by the walk and it is not serious. Vet says he looks great at trot and canter so no problem.
Friend wants his neck and back xrayed. Vet thinks this is a waste of money, but goes ahead and does the xrays.
Friend is in the waiting room, and sees the vet come out and bring in a couple other vets to the xray room. Friend knows something is up.
Later vet comes out and says "I don't know how to tell you this, but your horse has a broken neck".


This is not something that can be treated. There is no way of knowing if this will progress to death or pain. Right now her worry is that he is in pain but continues to work.
The point of this post is that I would recommend to everyone that if your horse is having issues, get the neck xrayed. I believe a lot of disobediences are due to the neck having problems. Until fairly recently, nobody xrayed the neck and back on a PPE. I never did. Yes, it's expensive, but well worth it. My trainer told me that he has passed on a few european resale prospects due to them flunking the neck exam.
The other thing is this. When you see a quality horse being sold at a lower price, this is a red flag.