When we see a horse short-strided in front but improving with warm-up, or a horse pointing a front foot as if he has heel pain when he’s standing, our first thought is “navicular” — and we may well be right. “Navicular” is used to describe many problems that cause pain in the horse’s heel. Because the navicular bone is part of a complex joint — the coffin joint down in the hoof — a number of things can go wrong, so finding the right treatment for your horse requires a specific diagnosis, excellent farrier work and pain control.
The navicular bone is a boat-shaped little bone that acts as a fulcrum for the tendons in the foot. As such, the bone is subjected to stresses from many different sources.
The frog and digital cushion offer some protection, but if these structures atrophy or stop functioning, the health of the navicular bone is also at stake. In addition, the deep flexor tendon runs down the horse’s leg along the back of the navicular bone, which means stresses to the tendon can cause problems down into the hoof as well.
Prevention And Detection
Good management is at the heart of navicular-disease preventation. A proper hoof angle, farrier work, turnout and exercise are basics. Proper nutrition and body weight are also important, as overstressing the joints can contribute to navicular problems.
Like any condition likely to involve both front feet, early detection is often difficult because the horse may still move evenly. But a horse with heel pain will step flat-footed or land toe-first. Another clue is a shorter stride. Stumbling is common, and he may seem to hold his head higher and more rigid than normal.
In time, the heels and frog will begin to shrink. Shoes will also show more wear than usual at the toe.
The horse also may show intermittent lameness. In the early stages, he may even seem to warm up out of the lameness when worked. He may point one hoof when resting or rest with the heel slightly off the ground. If both feet are equally affected, he may point one and then the other or even lie down more often.
Common Contributing Factors
Conformation problems that increase concussive forces on the hoof and poor farrier work will eventually compromise the frog, heels and digital cushion, causing navicular-bone pain. If your horse’s build, hooves or work predisposes him to navicular, begin preventative measures immediately.
Predisposing factors include:
Little Hooves: A large/heavy horse with relatively small feet may overload the distal joints. In addition, a heavy horse is more prone to overstretching the deep flexor ligament, which then “pinches” the navicular bursa against the bone.
Navicular Bursa Irritation/Low Heels: When the navicular bursa is squeezed between the deep flexor tendon and the bone, it can get irritated. Work at speed and/or trimming or shoeing with too-low heels causes increased stretch on the tendon and inflammation, which may then spread to the navicular bone.
High Heels: When heels are too long, the shock-absorbing ability of the frog expansion and digital cushion are lost. Blood circulation is reduced, which results in the atrophy of these structures and further narrowing of the heels.
Contracted Heels: When the heels narrow, the hoof structures can’t expand normally and absorb concussion. Circulation is reduced as well. Hoof Balance: Lateral, or side-to-side, imbalance can result in navicular-area problems. If you look at an imbalanced foot from behind when it’s on the ground, you’ll note one heel is lower than the other. This compression will affect the way the navicular connects to the coffin bone and put more strain on the area where the suspensory ligament of the navicular attaches to the bone.
Long Toes: A long toe, especially on a shod foot, delays breakover, lengthening the amount of time the deep flexor tendon is in maximum stretch and compressing the navicular bursa. It is especially bad when coupled with short heels, which also increase the stretch/compression.
A combination of diagnostic techniques should be used to determine if your horse has navicular and what type of treatment is best.
The veterinarian will do a lameness evaluation, meticulously examining the hoof and observing the horse’s posture and movement. He or she will use hoof testers, which put pressure on different areas of the hoof to determine sensitivity, and often a nerve block, which involves injecting a temporary numbing agent to a particular nerve, to determine the extent of the disease. If the horse travels sound with the nerve blocked, the veterinarian knows he or she pinpointed the location of the pain.
The next step is X-rays, although they don’t tell the whole story, since some radiologists consider navicular changes normal in horses over 12. However, the vet will look at the relationship of the various structures in the foot, as well as the condition of the navicular bone itself.
Once the diagnosis is made, proper trimming or “corrective” shoeing may be employed. Shoes with a wide web and easy breakover, such as a rolled toe, will help absorb concussion and relieve stress on the navicular and are indeed therapeutic. Pads and packing also absorb concussion, again therapeutic.
The goal is to get the horse’s hoof angle and balance back where it belongs naturally. Raising the angle of the hoof will make the horse more comfortable as it relieves pressure from the deep flexor tendon. However, raising heels beyond the normal angle for the horse is usually counterproductive and should be avoided for all but the most advanced cases of navicular disease.
Bar shoes can help a horse with contracted heels and frogs with little inherent shock-absorbing capacity. You should still have your horse’s heels trimmed to a normal length and the shoe fit full to encourage expansion and better circulation.
Sometimes the best course is not to shoe at all. We believe that, for many horses, going barefoot — with proper farrier work — is the most effective, rapid way to reverse heel and frog contracting. This is ultimately a judgment call for the veterinarian and farrier, however. When navicular disease is longstanding and extensive, dramatic changes in the horse’s hooves may not be possible.
While mechanical therapies concentrate on structural support, medical therapies are necessary for pain and/or increase blood circulation to the foot. Phenylbutazone is widely used because it works well, but we’d save it for occasional use. Long-term use has a high incidence of side effects, most notably ulcers.
Some herbal anti-inflammatory/analgesic preparations help navicular horses, especially those containing devil’s claw. We especially like the response to the pricey herbal Navilam O (Emerald Valley 888/638-8262/$67.95 for one liter), which combines devil’s claw and hawthorne berry, a peripheral vasodilator. MSM may also help.
Warfarin, an anticoagulant/“blood thinner” also known as Coumadin, is popular, but blood monitoring is necessary, as overdoing it can lead to major bleeding problems.
Although not as dramatic as warfarin in terms of anticoagulation, aspirin is often a good choice for horses with navicular, both for its anticoagulant effects and as an anlagesic.
Isoxuprine, a common navicular remedy, dilates peripheral vessels. Initial enthusiasm over it has waned somewhat, and it’s also illegal in competition. Other, less frequently used drugs for navicular include pentoxifylline and nitroglycerin.
Joint nutraceuticals aren’t a good choice, as they target joint cartilage, and many navicular cases don’t even involve the articular cartilage.
Corticosteroid injections of the navicular bursa do give effective, albeit temporary, relief. They come with the risk of infection and delayed healing processes, but the benefits may outweigh the risks for some horses. Consider injections if your veterinarian suggests them, but if your horse only gets a few weeks of relief it isn’t a path we’d repeat.
With alternative therapies, we’ve found magnetic bell boots relieved pain in less than 50% of horses we tried them on and the pain rapidly returned when the boots were removed. The Respond Bio-Pulse provided noticeable improvement in lameness and freedom of movement after about the third day of therapy. We also had results with the Chi machine, local treatment. (See November 2001 for further information on these therapies.)
Also With This Article
Click here to view "Use Smart Navicular Strategies."
Click here to view "Surgical Neurectomy And Cryotherapy."
Click here to view "Typical Navicular Case Scenarios."
Click here to view "Common NavicularX-Ray Findings."