Thanks. Blue. I was just trying to think this through. even if the knee doesn't act painful, the fact that there is squishyness indicates there is "something". maybe not a big deal, but maybe it is. An xray shouldn't be too expensive. I think I paid $35 or so for one the last time I was in. And then you'll have an idea what you're dealing with.
in combination with the rearing thread. You really need to know if she's dealing with pain or not, because if she is, she's going to get real dangerous if you keep working her and you could end up in the hospital or worse.
if she's not dealing with any kind or pain or issues, you need to be very firm, even harsh with her, to keep her moving forward instead of rearing. You also need to be doing lots of slow work with her. what i call "brain food", in-hand gymnastics and exercises to earn her trust and respect.
I agree with who said she's naturally an alpha mare and IMO they make the best horses, but you have to have a clear understanding of who's in charge and you don't have that with her.