Navicular disease often begins as an inflammation of the bursa between the deep digital flexor tendon and the navicular bone of the foot and is a common cause of lameness in horses.
Signs of navicular disease
While walking, the horse with navicular disease tends to place its weight on the toe to avoid placing pressure on the heel area, which contains the inflamed navicular bone and bursa. Since the horse does not place weight on the heel, it takes longer to stop the stride. While standing the horse tends to shift its weight continuously. This relieves pressure, and thus pain, on the heel areas. Since the horse tends to place its weight on the toes during movement, the gait is very rough and sometimes gives the appearance of lameness in the shoulder. The horse is often lame after work, but the lameness may disappear with rest. Because there may be comparably poor circulation in the foot, the heels and adjacent hoof may become smaller and contract.
Poor circulation associated with navicular disease can cause the affected foot to become smaller
A veterinarian should be contacted when signs of lameness are noticed. Most veterinarians use hoof testers as an aid in the diagnosis of this condition. Applying pressure with hoof testers over the frog area produces pain, and the horse may flinch if the disease is present. The hind feet should be tested with hoof testers to compare the reaction with that of the forefeet.
A locally injected anesthetic that temporarily blocks the nerve supply to the affected area will relieve the pain for a short period of time. In this way the veterinarian can determine whether or not navicular disease exists. If the horse was lame before the injection, and walks normally after the injection, it may be assumed that the lameness is located in the navicular area.
Corrective shoeing is helpful. A bar placed across the heels aids in relieving the pressure on the heels. Rasping the quarters of the hoof wall or cutting grooves in the wall aids in relieving foot contraction. Rubber frog supports (properly applied) may be a superior method of restoring frog pressure. Cutting the nerves that supply the navicular area may be effective also, but can lead to several complications and therefore should be performed only when other approaches fail.
While the outlook for horses with navicular disease is unfavorable in most cases, the various methods of treatment discussed above may prove sufficiently effective to reduce the suffering of the horse and extend its useful service.