The reason for this post is a comment which was made to me a long time ago by an owner who had a nice showjumper which had been diagnosed with navicular. She wanted me to look at the feet and give her some advice and was prepared to put lots of effort into helping the horse improve.
As is often the case, the horse had a very weak, under-developed caudal hoof but there were lots of good points about the feet as well and the owner was fortunate enough to have great facilities with lots of different surfaces which she could work the horse on.
After listening to me describe the sort of work and exercise level which I thought would benefit the horse, the owner sighed and said "I'm not prepared to work a horse which isn't sound". I explained that the weak areas of the hoof would only become stronger with work, and that all work should be within the horse's comfort zone; I reassured her that she would not be pushing a horse to work on surfaces or at speeds which she couldn't cope with, but she was adamant. As a result, of course, the horse never improved.
I think there is sometimes a tendency to look at soundness as an absolute - a horse is either sound or it isn't - but the reality of course is that soundness is not black and white. We've all come across horses who start off a bit stiff but loosen up beautifully once they are moving.
In the same way, the rehab horses who come here are far from sound when they arrive. If I, or their owners, refused to do anything with them until they were perfectly sound we would be waiting a long time, because in fact the improvements in soundness which we see are a direct result of correct, comfortable movement.
Its a virtuous circle - the more a horse is able to move correctly, the better his hooves become, the better his hooves become, the more he is able to move correctly.
There is a saying among classical trainers that, with any piece of training, you are either improving a horse or damaging a horse. You can say with equal truth that with every step a horse takes, he is either strengthening or weakening his body.
Just as with training a horse, building soundness (or creating lameness, for that matter) is not something that happens in a day - its a gradual, cumulative process consisting of many small movements.