I let her out on the field, so she can move. She always trots in the beggining but she didn't yesterday, so that means something hurts. After few hours I get her back in the stable and I checked how she walks and trots and it was better. It wasn't obvious, and if I didn't know how she walks normally, I'd say she's fine. When she was out in the evening she also trotted agressively to get pony away from hay, but when I get her back in the stable she was back to obviously lame. This morning she's almost fine... We'll see how she'll do in the evening.
Is there any scale about lameness?
Last year something similiar happened, although not when I was riding. She was ok in 8 days though...