First of all - this isn't a big deal and I have it under control. I'm just asking for opinions as to what might have caused it, because it's a bit of a mystery and I'm curious : ]
I took my mare out of her stall this morning and her back legs were extremely sore - the right more so than the left. She doesn't want to put any weight on them whatsoever... even if she's just standing there she'll hold them up periodically like they're broken. She only holds her left leg up for a second at a time - the right is obviously much more sore.
Both fetlocks are swollen as if she's stocked up, and there's some heat in both. She does tend to stock up if left in her stall overnight, but she was out last night so there's no way that's what it is.
She has some grunge on her lower legs which was not there on Monday (I'm not sure about Tuesday). I know grunge can cause lameness, but can it be that severe? And with heat/swelling?
I scraped off all of the grunge and applied an anti-fungal spray. For the swelling, I just hosed off her legs with cool water for a while and put her back in her stall. She's going to stay in tonight, and I'm going to play it by ear.