There was a great post a while back by Tony I think it was, with pics, of a foal with weak legs that straightened right up in no time.
I have had a couple also over the many years that were pretty cockeyed, and it is shocking how FAST they improve every single day, to be good as new in no time. Have seen many from many farms, Minis and full sized alike.
They build muscle tone every day, and if you took a photo of each day, from the same angle, you will be amazed!!