Heel Pain in Horses

Your previously normal horse has developed lameness, which you notice as a stiff, short-strided gait that is worse on the turns and worse on hard ground. Giving your horse phenylbutazone (Bute) dramatically improves the signs of lameness for a period of time, but the lameness persists and gets slightly worse. With these clinical signs, the fear of many horse owners is that the horse is developing navicular disease, and that the horse's career might be finished. Obtaining a very accurate diagnosis is very important in these cases, as numerous conditions or problems other than navicular disease can lead to similar clinical signs.

Historically, navicular disease has referred to a chronic forelimb lameness resulting from pain originating in or near the navicular bone, with horses often having abnormal radiographic signs involving the navicular bone. With the dramatic changes that have taken place in the imaging of bones and soft tissues (scintigraphy, ultrasonography, computed tomography or CT, and magnetic resonance imaging or MRI), we have learned that a wide variety of tissues other than the navicular bone can be involved in creating pain in the heel region of the horse's foot.

Anatomically, the navicular bone acts as a pulley to redirect the direction of the forces that are applied through the deep digital flexor tendon (DDFT) as it courses to attach onto the distal phalanx (coffin bone) within the foot. The navicular bone is suspended in this position by supporting ligaments, both on its proximal (upper) and distal (lower) surfaces. Between the DDFT and the navicular bone lies the navicular bursa, a small fluid-filled sac that ensures good gliding motion between these two structures during locomotion. In some horses with pain originating from the heel region of the foot, only one of these structures might be involved. In other horses, many of these tissues can be involved. The diagnostic workup is structured to help determine which of these tissues or structures might be most important in a given case so that the most appropriate imaging modality can be used, and the most appropriate treatment can be given.

So, the commonly asked question, "Does my horse have navicular?" is not as simple as it might seem at first glance.

Not all of the imaging modalities need to be used on every case to come up with an appropriate working diagnosis and treatment plan. Also, some cases can develop heel pain and have no detectable changes using any of these imaging modalities, even if all of them were available and were employed. Used appropriately, however, they can provide important information on selected cases, particularly those that might not have responded as expected to treatment.

Many conditions that cause heel pain can be successfully treated, so a "heel pain" diagnosis is certainly not an athletic death knell for many horses. Some horses confirmed with navicular disease itself can also be treated successfully and continue with useful careers, at least for a period of time. Sometimes a shoeing change that improves breakover of the foot, that decreases strain in the deep digital flexor tendon, and that provides better heel support will result in significant improvement. Some horses, depending on their individual conditions, will improve after medication is placed in the coffin joint of the foot. A smaller (but still important) group of horses will respond favorably to medication placed in the navicular bursa (the small fluid sac between the back of the navicular bone and the deep digital flexor tendon). Neurectomy is a surgical procedure to remove a section from the nerves that serve the heel region of the foot, thereby at least temporarily removing the sensation of pain from this region. Based on personal observations as well as anecdotal feedback from other veterinarians, it seems that the use of this surgical procedure might be less common than in previous years. This also attests to greater successes with some of the other treatment approaches, possibly due to more accurate diagnoses.

The best way to avoid having a horse develop heel pain is to ensure that he receives proper trimming and shoeing throughout his career. This is also an area where more research funding and efforts are being directed. The biomechanics of foot function are better understood than before, and efforts are being made to determine how different types of trimming and shoe application alter function. Nonetheless, for horses which develop a heel soreness problem, getting an accurate diagnosis is very important in the determination of whether the problem can be corrected.

For more information on navicular disease, see page 91.

About the Author

Gayle Trotter, DVM, MS

Gayle Trotter, DVM, MS, is a professor in clinical sciences at Colorado State University. He is internationally recognized in the field of equine orthopedics.

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