The Navicular bone is rather small, about the size of a pretty small (like 2 peas) pea pod. It bears no weight. It doesn´t join any bones together and it very rarely breaks. It is accused of being the cause of all manner of crimes, though rarely guilty. So just what purpose does it serve? It is one of three sesamoid bones in the distal limb, the other two being being a small pair of bones at the top and rear side of the fetlock. Their purpose is to change the direction of the pulling force applied to a tendon. The job of the distal sesamoid bone, or navicular, is to ensure the pulling force, created by the DDFT (deep digital flexor tendon), of the coffin bone is always in the same direction, regardless of the angle of the pastern bones.
So, if a hoof consistently lands toe first to the extent it becomes lame, the navicular is blamed. The lameness is usually due to damage caused by heat in the DDFT and navicular because of this movement - Consider the hoof length and angle. An exaggerated heel first landing will also cause heat in the DDFT due to the greater distance it moves over the navicular bone, again the navicular being held responsible - Consider the hoof angle. The harder the ground on which a horse works, the less the hoof can penetrate it at the moment of contact, the greater the vibrations, again causing a rise in temperatures - Consider the terrain before accusing the navicular. Speed is another element to be considered when looking at a resulting lameness.
Of course the biggest crime the navicular bone is accused of is heel pain. Often labelled as navicular disease or syndrome at that point, with claims of degeneration of the bone itself. If there are no x-rays, there is no diagnosis. These claims can not be substantiated without an x-ray. But this is also now the time to look at the hoof form at the heel. Is it contracted? Maybe even sheared? Is the frog contracted? Do pathologies exist in this region? These are the structures that need good consideration and assessment before deciding a horse has navicular.
Touching wood not one of the many cases presented to me, which have been diagnosed as suffering navicular, have had any bone degeneration. With a program of correct diet, movement and remedial trimming, horses who were written off by both vet and farrier have returned to competition life or trail blazing with no further issues (in the navicular!). Please be sure to have X-rays, and 2nd and 3rd opinions if necessary, before making that tiny piece of collagen and calcium suffer the blame and writing off your horse.
(Navicular syndrome, or disease, is a very real pathology, yet depending on how it is diagnosed, or labelled, very much decides the subsequent treatments. At WHP we explain to our students the difference, the standard protocols associated and how we practice a whole horse approach to resolving the problem)
So, if a hoof consistently lands toe first to the extent it becomes lame, the navicular is blamed. The lameness is usually due to damage caused by heat in the DDFT and navicular because of this movement - Consider the hoof length and angle. An exaggerated heel first landing will also cause heat in the DDFT due to the greater distance it moves over the navicular bone, again the navicular being held responsible - Consider the hoof angle. The harder the ground on which a horse works, the less the hoof can penetrate it at the moment of contact, the greater the vibrations, again causing a rise in temperatures - Consider the terrain before accusing the navicular. Speed is another element to be considered when looking at a resulting lameness.
Of course the biggest crime the navicular bone is accused of is heel pain. Often labelled as navicular disease or syndrome at that point, with claims of degeneration of the bone itself. If there are no x-rays, there is no diagnosis. These claims can not be substantiated without an x-ray. But this is also now the time to look at the hoof form at the heel. Is it contracted? Maybe even sheared? Is the frog contracted? Do pathologies exist in this region? These are the structures that need good consideration and assessment before deciding a horse has navicular.
Touching wood not one of the many cases presented to me, which have been diagnosed as suffering navicular, have had any bone degeneration. With a program of correct diet, movement and remedial trimming, horses who were written off by both vet and farrier have returned to competition life or trail blazing with no further issues (in the navicular!). Please be sure to have X-rays, and 2nd and 3rd opinions if necessary, before making that tiny piece of collagen and calcium suffer the blame and writing off your horse.
(Navicular syndrome, or disease, is a very real pathology, yet depending on how it is diagnosed, or labelled, very much decides the subsequent treatments. At WHP we explain to our students the difference, the standard protocols associated and how we practice a whole horse approach to resolving the problem)
 Original drawing by James. R. Rooney DVM |  See the tiny culprit? |
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