This makes me wonder if I've ever treated anyone this way. Unfortunately I think I have. Not because I think people in your situation are monsters though.
It's because when many people see someone with a disability or in pain, they are not sure how to react. Should they act as if nothing is wrong? Behave as though they're talking to an able-bodied person? Should they offer help? Should they offer encouragement?
The easier thing is to just ignore, because that way at least they're less likely to do or say something "wrong". It's the bystander effect.
But if they don't ignore, they don't know what the "right" thing to say is. So what comes out is often awkward and can make things worse.
So if you're comfortable answering Shannan, would it be better for people to treat you as if you're not disabled and in pain? Say "how's it going" and chat lightly like they would to a random person they met at the gym? Would that be insensitive if you're visibly in pain? Would it be better to ask if we could offer help instead?
I want to become better at treating people with visible disabilities the way they want to be treated. My gut feeling is "just treat them like anyone else" and that's what I normally try to do but in the case where someone is clearly struggling or in pain it becomes more difficult to know whether "acting the way I would to a nondisabled person" is actually invalidating the disabled person's experience or making them feel less seen?