Hope for Navicular Horses

Know the injury to your horse's foot before calling it "navicular."

In earlier years, a diagnosis of navicular disease was often considered career-ending for a horse. Chronic lameness was typical, in spite of therapeutic shoeing, medication, etc., and sometimes the only option to help the horse travel sound was a neurectomy (the cutting of nerves leading to the foot), which meant he would no longer feel pain (or anything else) in the foot. Today we realize that what we earlier called navicular disease (the horse showing palmar--toward the back of the foot--foot pain, positive to hoof testers over the navicular area, and going sound after a posterior digital nerve block) includes a host of different problems within the foot, some of which are unrelated to the navicular bone and/or bursa (the fluid-filled sac that cushions the navicular bone against the pressure of the deep digital flexor tendon). The term navicular syndrome or palmar foot pain is now used instead.

Some cases of navicular syndrome have a good prognosis for healing and full recovery, if given time and proper treatment. Yet, for many years accurate diagnosis was elusive since it's difficult to view the inside of a living horse's foot. Ultrasound, X rays, and nerve blocks have been used to aid diagnosis, but results of these tests can be misleading or inconclusive.

Stephen O'Grady, DVM, MRCVS, owner of Northern Virginia Equine, says a posterior digital nerve block basically anesthetizes the entire foot. "When you block that foot and the horse goes sound, is the pain coming from the navicular bone, the navicular apparatus (the suspensory ligament, which anchors the navicular bone to the second phalanx, the impar ligament, which attaches the navicular bone to the coffin bone, etc.), a lesion in the deep digital flexor tendon, the bursa of the navicular bone, or the coffin joint?"

The next step usually is to block the navicular bursa. "This localizes the pain to this area (the navicular bone and navicular apparatus)," says O'Grady. "Then we could look at radiographs, taking five to seven views of that foot from different angles. If we find a lesion--along with clinical signs, diagnostic nerve blocks, and maybe a certain type of foot conformation--this gives a little more credibility for a diagnosis.

"But, more often than not, radiographs are so-called normal or inconclusive," he adds. "You can't see any pathology in the bone. Or there might be visible remodeling changes in the bone of a perfectly sound horse."

Most athletic horses will have some changes because bones are always remodeling and adapting to stress.

"Over the years, our treatment for navicular disease was to change the shoeing, inject the coffin joint, put the horse on Bute and a modified exercise program, and see how it went," says O'Grady. "And often this regime would be unsuccessful."

Enter MRI

With the advent of MRI, we are finally able to look inside the foot of a living horse in detail. Sarah Sampson, DVM, has been doing research on navicular syndrome horses at Washington State University for five years. "We've had a high-field (MRI) magnet here for 11 years, and MRI has brought to light various problems that occur in these horses," says Sampson. "Many of the things we were never able to diagnose in live horses we are now able to see.

"They fall into different categories based on the pathologic changes, and this has given us ideas about new ways to treat them," she says. "Some have bone damage, others have tendon damage (to the deep digital flexor tendon), and others may have a ligament involved (the collateral sesamoidean ligament, impar ligament, or collateral ligament of the coffin joint), yet they all block to a palmar digital nerve block and present the same on clinical evaluation during a lameness exam.

"We've even had horses that had lesions within the distal (lower) part of the digital flexor tendon sheath, or osteoarthritis in the pastern joint," she continues. "This information has opened our eyes to new ways to treat these different horses. We have funding from the American Quarter Horse Foundation to look at treatments for horses with damage to the collateral sesamoidean ligament--which has proven to be a common pathology in horses with 'navicular syndrome.' Some horses have only one structure affected within the foot, and others have a multitude of structures affected at the same time."

O'Grady says we can now find what's actually wrong in the foot, if an owner has the means to utilize MRI. "We are finding lesions in the impar ligament that attaches the navicular bone to the coffin bone, damage in the suspensory ligaments to the navicular bone, edema (fluid swelling) in the bone itself, adhesions from the cartilage to the bursa, or lesions in the bursa," says O'Grady. "More than anything, we are finding tears in the deep digital flexor tendon within the hoof capsule, where it attaches to the solar surface of the coffin bone, which we could never image before.

"In the majority of cases, MRI can give you a definitive diagnosis, and also a prognosis," says O'Grady. Knowing what the problem is, you'll know whether the horse can recover. In many cases there is good prognosis if the horse is given enforced rest to allow healing from the specific injury.

A diagnosis of "navicular disease" used to mean the horse was probably doomed to early retirement. But now veterinarians are finding that a lot of these horses don't actually have a problem with the navicular bone. "They have a tendonitis or an injured ligament," notes O'Grady. "These can heal, if given time."

The old practice of treating "navicular disease" with egg bar shoes/wedge pads, and medication was not always successful. "In my opinion, the main reason these treatments were unsuccessful is because if there is damage to tissues, the horse needs time to rest, time for the tissues to heal, and time for the medications to work," he says. "But owners don't do that if they want the horse to go jump or race next week."


Once an accurate diagnosis is made, vets/farriers might be able to figure out how to take some of the stress off of the affected area of the foot. "If there's a lesion in the deep digital flexor tendon, we'd put a longer shoe on the foot, with heel elevation," explains O'Grady. "If there's a tear in a collateral ligament (such a ligament connects bones between joints), we'd put on a shoe with a little more ground surface under the affected ligament to support it and bevel the opposite side to aid breakover. If it's an injured impar ligament, you try to figure a way to get the stress off the ligament."

There are many ways to treat these horses with farriery. Given proper rest and using biomechanical farriery, many horses can recover. But to treat effectively, you need to know what the problem is and understand the horse's foot conformation. It will be different for every horse. The reasons for lameness can be varied, so the treatment will also vary.

"If we find an adhesion between the navicular bone and the bursa, this can possibly be treated arthroscopically (with surgery), or we can inject steroids in there to try and break down those adhesions," says O'Grady.

Sampson adds, "In horses that do fall into the navicular syndrome category (problems with the bone and its associated ligaments), after we MRI them, we can determine whether to inject them and where to inject them. If it's a recent tendon injury, we may decide that a rest program may be helpful. With MRI we find that a lot of tendon injuries extend up into the digital flexor tendon sheath. That gives us another option in treating them--to put steroid and hyaluronic acid into the digital flexor tendon sheath, which is something we can do at the fetlock region. Some horses we can send home and the sheath can be injected multiple times by the owner's own veterinarian."

This was not an obvious option until these horses were examined with MRI.

"We can also determine, from the MRI, whether we think coffin joint injections will work, or if we need to spend extra money to do navicular bursa injections," she adds. "We can now give the owner more information, with a solid reason for our recommendation--and they can make an informed decision on whether to spend the additional money."

Take-Home Message

O'Grady comments, "Farriery, medication, and rest are often the best ways we can deal with these problems."

He acknowledges that the term navicular disease is vague; there are many structures in the back of the foot that can be injured. Palmar foot pain is probably the biggest lameness problem that plagues the horse industry, and a correct diagnosis regarding the cause of foot pain is paramount to the treatment and future of the horse.

Sampson feels it's important for owners, trainers, and referral veterinarians to know how the insight MRI gives us can affect the way we treat horses. "Even cases we assume are navicular syndrome can surprise us when we do an MRI and discover what is actually going on in the foot," she says. "MRI needs to be used earlier in the diagnosis of lameness. This could save many owners large amounts of money that they are now spending on repeat lameness exams and blocks, repeat radiographs, joint injections, shock wave therapy, loss of use due to rest or continued lameness, etc. Obtaining a definitive diagnosis early in the course of disease can streamline the treatment and prognosis, and possibly improve the prognosis for return to competition."

About the Author

Heather Smith Thomas

Heather Smith Thomas ranches with her husband near Salmon, Idaho, raising cattle and a few horses. She has a B.A. in English and history from University of Puget Sound (1966). She has raised and trained horses for 50 years, and has been writing freelance articles and books nearly that long, publishing 20 books and more than 9,000 articles for horse and livestock publications. Some of her books include Understanding Equine Hoof Care, The Horse Conformation Handbook, Care and Management of Horses, Storey's Guide to Raising Horses and Storey's Guide to Training Horses. Besides having her own blog, www.heathersmiththomas.blogspot.com, she writes a biweekly blog at http://insidestorey.blogspot.com that comes out on Tuesdays.

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