At our barn we had a lady with a horse that was hard to saddle. He was the
best horse under saddle, once you got it on and SLOWLY girthed him up.
A chiropractor was at the barn one day working on the dressage horses and
the lady brought her little Qtr. Horse over and asked that the chiropractor take
a look at him. She did not tell this person about the difficulty saddling. The
chiropractor said his ribs needed adjusting and started to work on the horse. He
was so bad that the chiropractor had to work on him at several different
sessions but it solved the problem.
They still had to saddle him slowly for a while because it had become a
learned reaction... he was expecting pain. But after a few months, he was
cured.