If you watch the reining horses, they will pick up the pivot foot every turn and put it down in the exact same place to relieve the pressure from the pivot. For them to keep it in the exact spot and turn with weight on that one foot for several turns, it puts a lot of strain on the muscles, tendons, and the hock joint itself. If it is done alot, it will cause the horse to go lame.
Here is a pretty poor example because this horse moves his pivot foot around a lot but if you watch, he moves the weight off his pivot foot every turn. That is when he moves it, but a really well trained reining horse would put it back down in the same spot he picked it up from.