Navicular disease is, perhaps, the most serious malady to which the foot of the horse is liable. It is confined to the back part of the foot, where the large tendon (perforans) passes over the navicular bone just before its insertion into the sole of the pedal bone. It is most frequent in carriage and riding horses, and is brought on by severe exertion, or fast pace on hard roads, particularly if the feet are badly shod and the frog is not allowed to reach the ground. In some cases there is supposed to be a natural predisposition to the disease. The fore-feet are, it may be said, exclusively affected.

The feet are, as a rule, contracted at the heels, and hotter than usual. In the stable, or when at rest, the horse "points" the affected foot {i.e. he places it forward with the heel slightly raised), as that position gives it relief; if both feet are affected, he rests first one and then the other foot. In movement, unless the disease is very advanced, he may walk sound, or nearly so; it is in trotting, and especially on hard ground, and more particularly with a rider on his back, that he manifests lameness - stepping short, and going more especially on his toes. Because of this manner of going, the shoes are most worn towards the toes. The animal stumbles badly, and goes down hill with much discomfort; after working some time, the lameness passes off to a certain extent. Tapping on the sole, on each side of the frog, will produce pain, and pressure made by the thumb deep in the hollow of the heel will also cause pain and increase the lameness.

Treatment

Even in the earliest stage, treatment of this disease is seldom satisfactory. The wall of the hoof should be lowered as much as possible, so as to allow the frogs to rest on the ground; and, to this end, periplantar shoeing answers very well. Cold applications (such as poultices) to the feet, or compelling the animal to stand in cold water, a running stream, or in clay tempered with salt and water, may be resorted to. The stall or loose box in which he rests should be laid with peat, tan, or moss litter; and the food should be light, such as green forage, sloppy mashes, etc.

After a week or two of this treatment, a blister should be applied around the coronet, and especially in the hollow of the heel. Turning out on a damp meadow for a month or two may produce very beneficial effects. If the lameness still persists, however, a seton may be passed through the frog; should this not effect a cure, neurotomy (dividing the nerves of sensation on each side of the leg), by depriving the foot of feeling, will enable the horse to go sound, though it does not cure the disease. In many cases this operation is productive of much benefit, as it relieves the horse from great pain, and allows him to be utilised sometimes for years; care, however, has to be taken by the farrier in shoeing, lest he wound the foot by the nails; and injuries to the foot must also be attended to with more than ordinary care, as the animal does not feel any pain, and therefore does not manifest lameness.

It may be mentioned, however, that wounds and injuries heal as rapidly in a foot in this condition as in one which has sensation.