NAVICULAR DISEASE.
—A disease of the navicular bone and the structures surrounding it. It is called “coffin joint lameness.” This bone is situated at the back and inferior part of the coffin joint, and acts as a pulley over which the flexor tendon of the foot passes. Horses with upright pasterns are most liable to it, as more weight is thrown on this joint. Those shod with calkins on their shoes, which prevent the frog from coming in contact with the ground, therefore causing a shock to this joint, are also very liable to it. Some horses have hereditary tendency to this disease. Nails penetrating too deep through the sole, or anything that will cause inflammation of this joint, is likely to produce navicular disease. The most prolific cause is bad shoeing. By degrees the inflammation in a chronic form extends to other parts, causing a shrinking of the soft parts, resulting in contraction of the foot.
The lameness may appear suddenly and perhaps immediately after the horse has been shod, and is then usually thought to be the fault of nailing on the shoe. It is likely in this case that the smith has pared the sole and frog too thin, and that the part has suffered from a bruise by the horse stepping on something hard. After a rest it may disappear, to return after the next drive. Sometimes the disease is of very slow progress in one or both fore feet. The first thing that is noticed is that the animal points its toe, and if both are affected, first one, then the other. The animal may not be lame, but it does not step out so well as it used to, and by degrees the part gets more tender, until the animal begins to go lame, and the lameness gradually gets worse. There is a form of this lameness where the animal shows stiffness and lameness when first taken out of the stable, but, after being driven for a short distance, it passes off, and after it stands for awhile it will start off lame again. If this disease lasts for some time the muscles of the chest and shoulders seem stiff and may shrink. This has been called “chest founder” by horsemen. This is brought about by the soreness of the feet. The horse is afraid to step out, giving it the appearance of being stiff; the muscles of the chest and shoulders will shrink from want of proper action, caused by the feet being sore. If there is heat and tenderness in the hollow of the heel or a redness of the sole, and an absence of any other disease of the foot or leg, we may consider with almost a certainty that it is a case of navicular or coffin joint lameness. The result is contraction of the foot.
Take off the shoes, so that the frog will rest on the ground, then poultice the feet with bran, made up with cold water if it is a recent case, but if it is of some months’ standing hot water is better than cold; put the poultices into bags made a little larger than the foot; put about two inches deep of the bran mash into the bag, then put the foot in and fill in all around as high as the fetlock, and tie the bag above the fetlock and around the ankle to keep it well on the foot. Wet this several times a day and change it once daily. Continue this for two weeks, and see that it is properly done; if not, it will be of no service. Then blister the coronet with cantharides 2 teaspoonfuls and lard 4 tablespoonfuls. Repeat in three weeks, and give the animal a long rest.