Unexplained Cuts on hind legs??

My barrel mare has been getting tese cuts on her hind legs. My pasture is clean (no wire or metal). I thought maybe she was knicking herself with her shoes. So I got them pulled off. They are only on the inside of her hind legs. Its sounds silly but I just have no idea how she's cutting herself. They arent super deep just deep enough to cause a little oozing. Any Ideas?? Thanks to all who help :)

Are there small trees in there, that she could be straddling to scratch herself?

That will cause marks like this.

And if flies are bad? She could be brushing at them and causing them too.

We have small trees and the flies are bad. I've been taking her out during the day and putting her in a small pen with a shelter that we have to avoid the sticks. But I feel bad for having to keep her in there since we only have one pasture

Does she happen to have any feathers? All my feathered horses get a trouble called 'scratches' in the muddy season. It's a fungus that grows on their legs because the feathers prevent their legs from drying completely. I wash their legs with iodine solution then thoroughly dry them and put desitin (the diaper rash lotion) to help keep it dry and fungus free. I also keep them in during the bad mud and use pelleted bedding so their stalls stay exceptionally dry.

My pony gets scratches on occasion too even though he only has a little tuft of feathering. So I suppose it can happen on non-feathered horses too.

And for those of you out there saying 'what type of swamp are you keeping those horses in' :P They're moving in 2 weeks. My belgian gets bad scratches though because he pee's on his front legs xD silly boys!

No she I actually don't even need to keep her trimmed up on her feathers. Im not quite sure what it is. I was watching the horses playing the other day. While the other horses took caution running through the woods she just plowed right through. So now im wondering the the sticks are knicking her. Im not sure. I guess ill have to go pick up the millions of sticks and see if it helps any. Lol. Thank you both for the advice :)

If they're just on the insides of her legs, she's probably whacking herself with her hooves to get the bugs off.

My boy has been cropping up with unexplained cuts and abrasions on the outside of his legs, and I'm pretty sure they're from sticks and rocks in the turnout. He itches from the flies, he rolls around, he gets a scrape. I went through and took out all of the sharp-ish rocks I could find. It's New England, so there's no chance of getting rid of ALL of the rocks, more's the pity. That helped a bit.

But I'd be willing to bet a sawbuck that you're seeing self-induced hoof abrasions there...