Horse lameness

Hey all, my daughter is trying out a horse to possibly buy but we brought him home and he was lame. We found out he had major thrush and have been treating him for that and it's much better but he is still slightly off on his left. His right is sound. He seems to have been getting better the more he gets ridden. He hasn't been worked like this in almost 2 years. What do you think it could be?

Sorry, could be a multitude of things. If the horse is on trial pending the sale, I highly recommend a vet exam, could be something easily treated or could be big vet bills and a unsound horse. It is always recommended to get a PPE before you buy.

Could be anything from a bruise to an abscess to navicular... etc.

Any heat or swelling?