I've had the vet out to see what I can do about it, and he basically said that she'll probably have arthritis in the future and to put her on a joint supplement. (Which she was already on one at the time.)
The Maxflex XR doesn't seem make any difference with the fluid build up, and she's still stiff when you pick up her hind legs and occasionally when she canters. She's not stiff when she canters if she's excited, but any other time she's stiff. Now it's not noticeable to most people. I doubt anyone would even notice if I didn't tell them. I've just owned her long enough to be able to see her happy/regular canter from her slower/stiff canter.
I want to try magnetic therapy, but I'm not sure if it'll make a difference?
I do still want to keep her on a joint supplement, but something stronger. Maybe Cosequin, or one person I talked to suggested Adequan?
Another person said that maybe all she needs is a good liniment?
If anyone has any suggestions, or who has dealt with a horse with this problem PLEASE leave a post. This is driving me nuts!