The Achilles Heel

You’ve been noticing that your horse has a slight “gimp” to his stride. You’ve been noticing it for several months. At first you thought it was just your imagination, but now you’re certain that what you are seeing is real. So you decide to take him to the vet. Your vet does a full lameness workup with nerve blocks and radiographs. And then comes the diagnosis. Navicular. The horror! This word has haunted horse owners for years, and is practically taboo to anyone in the performance world. But really, Navicular is an outdated term, and can be a lot less scary than you think.

The term “Navicular” comes from the tiny bone that sits within the hoof capsule, just behind the coffin bone. It was originally thought that all Navicular cases were due to pain coming from this bone. However, with the advent of MRI, we’ve discovered that the navicular bone isn’t necessarily always the source of pain in these horses. There are a plethora of ligaments and soft tissues also involved and happen to reside in the same area as the Navicular bone. Nowadays, veterinarians are not using the term “Navicular” anymore. They’re replacing it with the term “Caudal Heel Pain,” among others.

So let’s talk a bit about what structures can be involved. Above is a picture of a horse foot if you were to look at the foot from the front and then cut it in half, straight down the center line from top to bottom. Opening the foot up, you would see this image. The structures that are labeled in this picture are the ones most commonly affected when we are talking about Caudal Heel Pain. As you can see, it’s not JUST the navicular bone back there. There’s also the Deep Digital Flexor tendon, the Navicular Suspensory ligament, the Impar ligament, the T-ligament, the Navicular Bursa, the digital cushion, and the coffin joint. All of these structures can be involved when a horse is diagnosed with Caudal Heel Pain. So when you think Navicular, don’t think JUST bone.

So how do we find out what structures are affected? This is a bit more difficult, and can accrue some costs. The first stop is X-raying the area. While much of Caudal Heel Pain is soft tissue, we can still get a lot of information about the health of the area based on the views we take. Good Navicular x-rays involve a picture from the front (called a DP), from the side (called a lateral), from the top (called a solar margin), and from the back (called a navicular skyline). These views allow us to assess the orientation of the bones to each other and to the hoof wall, the health of the navicular bone, and it allows us to see if there has been chronic damage to the area as indicated by calcification of some of the soft tissues. From there, some veterinarians have the ability to ultrasound SOME of the structures. However, ultrasound does not penetrate the hoof wall, so using it as a diagnostic tool is somewhat limited. The best option to know what is damaged and how badly is to do an MRI. This allows us to look at every structure within the foot and evaluate its health. But as we all know, an MRI of a horse foot is expensive, and not without risk. However, if done early on, a soft tissue injury can be prevented from turning into a chronic problem.

Ok, so my horse has been diagnosed with Caudal Heel Pain, but I can’t afford an MRI. What can I do? Some of it depends on how chronic your veterinarian thinks the issue is. If the issue is suspected to be soft tissue and very recent, your veterinarian may try rest and rehab first. However, there are other options that may also help. The number one thing to try is therapeutic shoeing. However, this is difficult because many farriers jump to one option: wedging the heel and this doesn’t always work, and can actually create more issues. Yes, wedging the heel in theory removes some of the normal pressure in the area, however, it may not remove enough to cause a difference. Also, many times, just a wedge shoe will actually crush the heels and make the horse more uncomfortable. If you are considering therapeutic shoeing, finding a podiatrist that can assess the angles of the foot and make changes based on x-rays. If you want more information on therapeutic shoeing, please see my March and April 2020 newsletters.

Many horses will also benefit from therapeutic medications which include joint injections, pain medications, and metabolism-altering drugs. The first line of defense is injecting the coffin joint with steroids, as this can take out some of the inflammation in it and the navicular bursa. Some may consider injecting the Navicular Bursa itself, to provide the most anti-inflammatory action in the area it’s needed. Along with this, your veterinarian may prescribe drugs like Equioxx or Bute, which reduces inflammation throughout the body. The biggest medication that can help some of these horses are bisphosphonates like Osphos and Tildren. These drugs alter bone metabolism, and can offer some of these horses relief by helping to stabilize the bony matrix in the foot. While not all horses may respond to one treatment, most horses will respond when you combine some of these methods.

Preventing caudal heel pain is not always a simple answer, as not all injuries are preventable. However, one of the best things you can do is have x-rays of your horses feet done early to guide your farrier in proper shoeing of your horse. Horses that have their foot in proper alignment and who aren’t putting excess pressure on the heel have less of a chance of injuring themselves in normal work. It’s also extremely important to find a farrier who is willing to work with you and your veterinarian to keep your horse as healthy and sound as possible.

While having Caudal Heel Pain is not ideal, due to advances in diagnostics and therapeutics, it’s not necessarily the career-ending problem that it used to be. Many horses, through the use of good podiatry and conscientious use of medications can maintain some semblance of rideabilty, if not make it back to the performance arena.