Agree with alllllll of this. I often think back and wonder if the grumpy/sour/naughty horses of my youth 25+ years ago were actually just in pain but no one found it or even tried very hard. I wonder about the same with my late mare.
Personally, I kept seeing NPA discussed on the forum and went “hmmm I’m glad I don’t have that problem! I have a great farrier and my horse has great feet!” and then when he had consistent trouble with hind end soreness from work the last few years, I tried all the things that made sense (bodywork, lameness exams, radiographs, physical therapy, joint injections, IM injections, saddle adjustments). They all helped to a degree, but it was still way too easy to make him sore at a level of work that everyone around me said should not make him sore.
I asked multiple vets if we should x-ray the hind feet to look for NPA and they all said no, his feet look good. Finally we did the x-rays and found the NPA.
Without the NPA being found, I easily could have carried on like this. He was never lame-lame. But now he feels sooooooo good under saddle and his lingering “always” bit of reaction to palpating his SI and lumbar area are gone. He’s easier to ride and feels stacked up over his hind end. Time will tell if this was “the thing” but I feel certain it was “a thing.”