(Warning, slightly off topic)
I have noticed that people seem to confuse navicular with laminitis/founder all the time. Even the people at my local feed store. They're like "too much sugar in feed can cause navicular." Um, not really! And my best friend too. "Can't put XYX horse on pasture because he will get navicular."
Now navicular isn't an easy disease to understand. But the basics are that it refers to heel pain in the horse, and it can be caused by arthritic changes to the navicular bone. The predisposition to navicular can be hereditary due to conformation.
Laminitis (inflamation of the sensitive lamini) can be cause by both excess sugar and/or concussion to the feet (also retained placenta in mares).
Founder is the rotation of the coffin bone that can result from severe cases of laminitis. Think of it as the internal structures of the hoof separating from the hoof wall because the lamini have come apart. Therefore the hoof wall can no longer support the coffin bone/internal structures like it should.
That is my laymen's farrier science lesson for the day.
To Phantomcolt18, bless you for trying to help this horse. Hugs!