Navicular Syndrome

Navicular syndrome is a soundness problem connected with pain in the heel area. "Navicular" horses display a "tiptoe" gait - trying to walk on the toes due to heel pain and to stumble frequently. The lameness may switch from one leg to another, and may not be consistent. Lameness usually occurs in both front feet, although one foot may be more sore than the other.

"Navicular" is usually diagnosed by taking x-rays of the navicular bone, diagnostic anesthesation of the navicular area and by putting the hoof on a wedge with the high end towards the front.

If the horse - besides tiptoeing and lameness - shows x-ray degenerations (bone loss) inside of
the navicular bone (bubbles, funnels) or other changes (ossifications), the diagnosis is set to navicular disease.
These changes of the navicular bone are made responsible for the pain in the feet. In case of holes and funnels, medication like Isoxuprine and Tildren are prescribed in order to increase blood supply to the navicular area and heal the bone.
Recently, much of the original literature concerning navicular disease has been called into question, particularly the significance of some radiographic changes.
Article No Hoof - No Horse

Dr. Strasser

In the 1990's, Dr. Hiltrud Strasser from Tübingen/Germany discovered that long bars, contraction of the hoof and various other deformations of the hoof capsule lead to pain in the heel or navicular area by bruising of the soft tissue. When the hoof is brought back to its natural shape, the navicular symptoms (pain, toe-first landing) disappear. Already existing changes of the navicular bone will however stay. Ossifications are the long-term result of unphysiologic movement (toe-first landing) and the resulting overload of the ligament inserts into the navicular bone while bubble-shaped holes are caused insufficient blood flow to the navicular area, thus the result of contraction and/or high heels.
Article Dr. Strasser

Dr. Bowker

In 1999, the research of Dr. Robert Bowker/Michigan State University has found that wild horses
growing up in the western USA (lots of movement on harder ground) do not develop navicular syndrome.
He attributes it to 2 factors:
- these wild horses develop tougher tissue in the hind part of the foot (digital cushion with tougher
fibrocartilage) as well as strong, higher bulbs
- these wild horses do not have high heels, their frog is strong and weightbearing.
Whenever he trimmed navicular horses to this "physiologic trim", the symptoms of navicular
syndrome disappeared.
Article Dr. Bowker

Trimming

Many hoof care experts around the world are working according to this research and helping
"incurable" navicular horses by restoring healthy shape, structure and function in the hoof.
The list of reasons for pain in the hind part of the foot and tiptoeing is long, the hoof care expert
has to find out the problem of the individual horse and act accordingly:

- high heels
- long bars
- weak, collapsed heels
- underrun heels
- vertical cracks in the bars
- heel contraction
- bar contraction
- sole contraction
- axial contraction
- too full sole
- sole inflammation
- abscess
- weak digital cushion
- weak frog that doesn't bear part of the weight
- fungal infection in the central frog fold
- long toes
- ... and the list goes on

Most of these conditions develop because of unnatural living conditions, shoeing, lack of move-
ment, lack of stimulation to the hoof (improper terrain) or incorrect nutrition. Equine podiatrist
KC LaPierre calls it in general the DHS (Deformed Hoof Syndrome).
So besides hoof trimming, the living conditions of the horse must be improved for stimulating
the development of a healthy hoof.

Trimming a navicular hoof

Some of the horses shown on the Signs of Pain page have been diagnosed with navicular.
Others which show the same symptoms are not, just because their navicular bone does not
show degenerations on x-ray. Trimming a navicular hoof is not different from trimming any other
barefoot horse. The main focus lies on:

- relieving pressure on the corium if contraction is present, but not at the cost of weakening
healthy structure
- encouraging the hoof capsule to regain its natural shape, but not forcing it there
- strenghtening structures that are weak/degenerated, but not at the cost of overloading

The horse above in a pityful position has been diagnosed with navicular syndrome and wears
special shoes with a rubber wedge. As you see, it doesn't really like to put weight onto its left
front. It is still being ridden, as it doesn't limp severely!
The shoe prevents that the hoof shape returns into its proper position.

This empty hoof capsule above is similar to the hoof of the horse above. It shows severe
deformations that may show as navicular syndrome. The natural shape of this hoof capsule is
indicated by yellow lines, while red lines outline the deformation:
- the coronet is bulged upward
- the horn tubules at the side wall are growing too far forward (about 2 cm!)
- as a result, the horn tubules at the side wall are about 2 cm too long
- the heel is tilted forward (underrun) and its horn tubules are also too long
- the central frog fold is pinched, the bulbs are too close together

From the inside, we recognize the dilemma:

The bars arch upward inside, far more than what is sometimes stated to be a necessary
natural "internal arch" and forms an incomfortable ridge, like a stone in the sock!
A natural internal arch (-> Article by KC LaPierre) would be able to act like a spring, the heels
would move backward upon loading and the arch would flatten, giving way to the descending
coffin bone. With the huge lever of these underrun heels, the arch is levered upward instead
upon loading, bruising and overstressing the bar corium.

This horse would have preferred walking on the toe, for sure.

For rehabilitation of this hoof, it would have been necessary to allow for an axial expansion,
without overstressing the remaining structures as good as possible. Well, too late...

In this cadaver hoof, the sole concavity was pushed upward by lack of function and formed a
huge unyielding arch that severely bruised the corium just underneath of the attachment of
the deep flexor tendon or the tip of the frog. I dug deep into the sole in order to find the cause of
the black horn formation, as the horse was already dead (you wouldn't trim a live horse in this way!). Cutting the hoof revealed the full amount of the problem.
-> dark sole horn in hooves with otherwise white sole may indicate bruised areas of sole corium!

Let's rather look at the rehabilitation of live horses:

Case 1:

Removing shoes, August 2006 - look at the axial contraction and the bulged coronet and compare to the picture of the empty hoof capsule further up. The resulting bruising from sole and bar contraction is easily visible, although the bars had been kept short by the farrier!

October 2006 - heels are much more upright and coronet is much straighter, bruising disappears.
White line is separation is recovering but has not reached ground yet (wall sounds hollow).

December 2006 - heels parallel to front wall, coronet almost straight - bruising mostly gone. White Line horn has recovered, though still a bit streched in the toe.

Case 2:

Another example of sole bruising around the frog is seen on this mare's front hooves, please notice also the dark discolouration of the white sole horn besides the red areas and compare to the axial cut above:

Shod horse in April 2006 vs. unshod horse in August 2006. She didn't feel perfectly comfortable
on gravel without boots yet, the corium was still recovering from the bruising and sensitive.

Rehabilitation:

The first horse had the red bruising areas clearly visible right after removing the shoes. That is good luck for the trimmer, because the owner can't say afterwards that this damage is due to too much trimming.
In the second horse, only the dark grey areas were visible as a sign of damage to the sole corium. There may even be nothing visible from outside at all.

The horses went immediately better after the first trim, but the second horse became sore after about
8 weeks, for about 2 weeks. That was when the hoof expanded. This may happen suddenly even without extreme trimming (well - expansion is the goal in the end), and does happen in many horses with "navicular" contraction. 1-2 weeks after the soreness started, the red inflammation areas became visible besides the dark areas. The bruised and damaged areas were inflamed/healing.

During such inflammation episodes, it is important to continue movement, if needed with boots and soft pads for comfort. Shock when hitting hard ground may be painful for inflamed tissue, just think about hitting a hard surface with an inflamed fingernail. Do not lock the horse into a stall, as this prevents circulation and might increase inflammation, but also don't force it to move at fast pace or over hard ground/stones. Just listen to your horse.

It is important not to panic or have made panic upon you by vets or other people in your stable. This soreness is not a return of "navicular inflammation", you don't need anti-inflammatory injections into the joints, as the joints are not the reason for the soreness. Also, don't blame the farrier, it is maybe not because of him doing something wrong.

Worst case scenario though is that the hoof itself is too weak - it might happen if you have an insulin resistant horse and feed sweet hay or other sweet feed, it might also happen with silage/haylage fed horses or horses that have been shod tightly for a long time. In these horses, the weak lamellar connection may give way and the coffin bone may sink onto the sole. The horse will be extremely sore
then and needs soft pads in the boots as well as a flat, slighty soft surface for a few months until it has regenerated.

I mention this because it has to be mentioned. There may be people out there with these kind of hooves, just reading these lines and trying to cure their navicular horses by ripping off the shoes and forcing the hoof capsule to expand. And then they'll end up with soreness, rotated or even with dropped coffin bones - which by conventional medicine cannot be cured (nature will heal it though) - so you should at least be aware of it!