I had her stifles injected which helped for one week. I started her on Pentosan and she has had 4 injections which I haven't really noticed any difference with.
Today I gave her a bath and turned her loose and she ran around bucking like a manic, lost her footing, flipped on her side and rolled over. (The ground was a little wet from last nights rain). Jumped back up and trotted off fine. I caught her and checked her out. No swelling, no lameness when trotting in a circle... But it scared the daylights out of me! She did the same thing about 4 months ago in the roundpen. I was working her at a trot, she took off bucking, and fell into the fence. (Nothing wrong with that footing as it is rarely used) It was wire fencing so the wire just bent out of the way. It was the same side as the one she fell on today.
I've had my other horse 13 years and have never seen her fall over while running in the field! She is retired and according to the vet probably has arthritis in every joint.
I'm starting to think I should take her to the vet school... Is it possible for EPM to be slow onset? But no other neurological signs- she can back, pivot, and you can pull on her tail... Some muscle loss on her topline, but she isn't being worked at all and the vet wasn't concerned.
Someone else told me to check her for EPSM as that can cause bucking and hindend issues. She is not a draft though. She is a Paint mare out of Hank a Chief and Easy Jet bloodlines.
The only other thing I can think of is that there is something wrong in her pelvis or stifles. My parents think I should just retire her and get a new horse. It just seems like there has to be more going on than just "arthritis".