when I was really struggling with my riding horse at one point, rodeo style bucking, etc, I got a chiro out. When I heard "your horse is the soundest, most even horse I've ever worked on, I can't find one thing to adjust", I was happy but at the same time my heart sunk.... it was really bittersweet... I was hoping for a magic bullet.
Turns out it was diet, ulcers & saddle fit, and rider error.
She is 10 but an OTTB raced til she was 5 and has poor hind end conformation (very straight), I have a feeling she will end up needing her hocks injected.
As for saddle fit could also be a real reason why her back is hurting, I currently am in the process of selling my saddle and using a friends right now. In the saddle I own there was outright protesting when I rode her in it but my in my friends not so much.
Idk for now we are going to check out the hocks and see how that turns out first, I just can't afford to go out and buy a new saddle right now. -sigh-
to address saddle issues -- get a good non-affiliated saddle fitter out. They might be able to make necessary adjustment in flocking or help you with padding to make your saddle work. Depending on what saddle you have and what you want, you might be able to sell and buy used without much outlay in additional money . . .