CEPS/Veterinary Extension
2938 Vet. Med. Basic Sciences Bldg.
2001 S. Lincoln Ave.
Urbana, Illinois 61802
Phone: 217/333-2907

By Linda March
Information Specialist
University of Illinois
College of Veterinary Medicine

The navicular (distal sesamoid) bone sits behind the coffin (distal phalanx) bone and is the smaller of the two bones in the horses' foot.

There are many possible causes for navicular syndrome. One is thought to be increased pressure inside the bone causing pain. There is also a chronic form of the disease thought to be caused by adhesion (scar tissue) between the navicular bursa and the deep digital flexor tendon. Another cause of chronic navicular disease is arthritis of the navicular bone and associated structures.

According to Dr. Carol Vischer, equine veterinarian at the University of Illinois College of Veterinary Medicine at Urbana, "The owner often thinks the horse has a sore shoulder, because it will shorten the length of its stride and move with a choppy gait."

Increased pressure inside the bone is thought to cause the horse pain. Concussion may also aggravate the problem. If the horse has to work on a rough or hard surface, the constant pounding of the hoof increases the pain. Other factors such as conformation, foot size, improper trimming of the hoof and obesity can all lend to navicular disease.

"Navicular disease usually affects fast-growing, large horses, such as Thoroughbreds, Quarter horses, warmbloods and some Standardbreds," Dr. Vischer says. "Ponies, Arabians and draft breeds are usually not affected," she continues.

Typically most victims are between two and 10 years old. Sometimes the problem is the horse is too big for the size of its foot. It is not always "big horse, small foot" though, nor is it really use-specific, but affected horses are usually athletic. Horses used to race, rope, compete in dressage, or barrel race are normally those which show the signs of intermittent front leg lameness associated with navicular disease.

"Navicular disease is one of the most common cause of front limb lameness. It is easy to diagnose, but frustrating to treat," notes Dr. Vischer.

Some of the methods veterinarians use to diagnose navicular disease are hoof testers, to detect pain in the heel area, radiographs to look for changes in the bone or bursa of the navicular bone, nuclear scintigraphy to detect bone and/or soft tissue inflammation, and heel nerve blocks. A lame horse that exhibits soundness after a heel nerve block may have navicular disease.

Once your veterinarian has diagnosed navicular disease, there are a few treatment options. Corrective shoeing with an "egg-bar" shoe is one. This type of shoe gives extra support to the heel. These shoes are usually made out of aluminum because it is a lighter material than regular steel bar stock. The owner should allow four to six weeks to determine if the change of shoes will be a viable treatment. If the bone has already started to change because of the disease, corrective shoeing may not help. Medications to increase the blood supply may also be given.

Navicular disease may also cause secondary lameness. The coffin joint may swell and become sore as a result of the problem with the navicular bone. Analgesic or other drugs for pain may be given, but caution should be used. Some of these drugs may cause ulcers and renal disease.

As a last resort, the nerve supplying the back of the heel may need to be surgically cut. If done correctly this is a safe procedure because the nerve to the toe is left intact. Therefore the horse is aware of its foot placement.

"Denervation may provide a temporary to permanent reduction of lameness," states Dr. Vischer.

Good foot care is very important to help prevent and treat this disease. The feet must be kept clean and properly trimmed and shod. Keeping the horse in good physical shape is also important. Obesity only aggravates navicular disease.

In some breeds, navicular disease may have an hereditary or genetic component. To help reduce the incidence, it may be wise to not breed horses confirmed as having the condition.

If you have any questions about navicular disease, contact your veterinarian.