Why does my horse cross his hind legs when standing?

Answer 1

If he does it all the time, it may be that it is more comfortabel for him, or he could be very pigeon toed.

If this is a new occurance, he may have joint issues or something could be hurting him to make him stand with his hing legs crossed.

He also may simply be scartching or stretching his hind legs if it is a habit that he only does for a few minutes when he is taken from his stall or something.

Answer 2

It could be simply his conformation; some horses are more inclined to have legs that are close together, and then on the other end of the spectrum there are horses that naturally spread their legs, simply because of their conformation. However, he could be hurt between his legs so he spreads them so that they do not rub the sore place. I advise getting a vet to take a look at him; better safe than sorry. It could be that he is sore or there are a number of other things it could be. His feet could be trimmed badly, he may be hurting in a different area far from his hind legs. Horses are really good at compensating for hurt places. Unfortunately, because of their amazing ability to compensate so well, we often don't notice something is wrong until it is really bad, and when we finally do realize something is wrong (that he is spreading his legs as he walks), we often think it is something else (that he is sore between the legs, etc.) whe he is really compensating for an injured, let's say... a front leg. Not saying that that is neccessarily true for your horse, but it is possible. So, get him checked out by a vet before passing it off as simply conformation.