Horse Disease Focus - Navicular Syndrome
What Is Navicular Syndrome?
Navicular disease or navicular syndrome is a painful inflammation that affects a horse's feet. It is almost always seen in the front feet and usually affects both front feet.
Navicular is almost never seen in the hind feet. It is seen more common in stock horses than in other breeds and is, thus, more common in the United States than in Europe.
A horse with navicular experiences pain in the heels. Therefore, the horse will stand with more weight on its toes. It may also shift its weight from one forefoot to the other.
The gait becomes short and choppy and sometimes navicular is misdiagnosed as a shoulder problem as a result. Navicular can also cause the hoof to become smaller. Although it almost always affects both front feet, one can be more severely effected than the other. Mis-matched front feet can be a sign of untreated navicular.
A horse with navicular will flinch when pressure is applied to the frog using a hoof tester. Vets may also use a local anesthetic to numb the affected area...if the horse then walks sound, it likely has navicular.
However, as navicular is a bilateral lameness, it can sometimes be hard for a rider to detect. I know of one case where navicular went completely undiagnosed, the horse concerned appearing completely sound, until the tendon behind the foot had been basically destroyed. The animal had to be euthanized.
Navicular syndrome is incurable. Once a horse has navicular, it will have it for the rest of its life. The prognosis is not favorable and it is inevitable that such horses will have shorter working lives.
However, there are management techniques that can be used to mitigate navicular. Lightening the work load and resting the horse when it is having a 'bad time' is important. Riding the horse correctly from rear to front reduces strain on the front legs. Horses with navicular are best ridden, thus, by experienced riders. A low dose of maintenance bute is often prescribed, to reduce inflammation.
The standard 'treatment' for navicular is to apply egg bar shoes. Unlike normal horse shoes that are open at the back, egg bar shoes go all the way around. They thus provide support for the horse's heel. Special pads are also sometimes used to take pressure off of the frog.
An alternative treatment has become popular in recent years, which is to leave the horse barefoot and trim the hoof in a special 'navicular trim'. Proponents of this approach believe that keeping shoes off helps keep the foot from becoming contracted.
Which approach is best may depend on the individual horse. In extreme cases, soundness can be preserved by 'firing' - cutting the nerves that go to the navicular area. However, this does not prevent further tendon damage and can mask other issues and cause the horse to become clumsy and possibly unsafe. Very few vets now use firing, and if they do, it is as a last resort when euthanasia is the likely outcome.
Causes and Prevention
Many studies have been done to try and find a genetic explanation for navicular. Its tendency to affect certain breeds more than others has led to some theorizing that there may be a 'navicular gene'. However, the evidence is that navicular is not based off of a specific genetic factor.
However, it does appear that navicular is 'genetic' in the sense that it is associated with certain conformational faults. Specifically, horses with navicular often have feet that are too small for their body and/or upright pasterns. Both of these traits are more common in stock horses, explaining the tendency for these breeds to suffer from the syndrome more. Halter-bred Quarter Horses are particularly prone to having feet that are far, far too small.
A good farrier and correct trimming and shoeing are vital to the preventing of navicular. The frog should not be trimmed excessively, although horses in humid environments or ridden on muddy soils often benefit from the removal of 'flaps' that sometimes form on the frog. Some people believe that horses that go barefoot are less likely to develop navicular.
Horses that are kept in stalls all the time and then worked hard are also more likely to develop navicular. For this reason it is often seen in racehorses, both Quarter Horse and Thoroughbred. All horses benefit from regular turnout.
Although there does not appear to be a navicular gene, epidemiological evidence does indicate that some lines are particularly prone to it. Therefore, a horse with navicular should not be bred.