My old pony had navicular. But didn't show any of the symptoms in the books and didn't fall into the category either. She was lame on both front legs intermittantly. Got Vet 1 out did lower limb nerve blocks which didn't stop anything. Advised field rest for 6 months. i wasn't happy with this and had vet 2 who took her into surgery and had xrays. Leisions on the navicular bone. Egg bar shoes, navilox and bute. Was fine and sound and ended up on no medication at all or special shoes. If I had listened to the first vet and turned her out for 6 months the problem could have been worse as the earlier you can catch it the better although you can't cure it. My mare still used to go short in certain circumstances. But was still being ridden, jumped, shown and winning right up to the end.