Overview: Navicular syndrome is also known as navicular disease. The navicular bone is a sesamoid bone that sits behind the coffin bone in the foot. The navicular bone is contained in a synovial bursa; the bone and the bursa function to cushion the deep digital flexor tendon (DDFT) as it courses down to attach on the coffin bone. Navicular syndrome refers to caudal heel pain related to the navicular bone, which can include the bone itself, the ligaments supporting the bone and/or adhesions between the navicular bone, bursitis and the DDFT. Navicular syndrome is most commonly diagnosed between the ages of 4 and 15 years of age. It is most common in Quarter Horses, Paint Horses, Appaloosas, Warmbloods and Thoroughbreds. The exact cause of navicular disease is unknown.
Clinical Signs: The degree of lameness with navicular syndrome can range from mild to severe and may be unilateral or bilateral. Most lameness is slow in onset and worse after work. However, lameness can develop acutely depending on the cause of pain. Horses with heel pain will often place most of their weight on their toes resulting in a "rough" gait. These horses may also shift their weight back and forth between their front feet. Many horses diagnosed with this syndrome have smaller than normal feet, contracted heels and/or a broken back hoof-pastern axis.
Diagnosis: A full lameness exam is required to diagnose navicular syndrome. A local analgesic may be placed in the foot to determine where your horse's pain is coming from. Radiographs are commonly used to diagnose navicular syndrome, but MRI is the gold-standard for a definitive diagnosis.
Treatment: Treatment involves controlled exercise and corrective/trimming shoeing. Many horses do well with heel support to help relieve pressure on the heel. NSAIDs (Bute, Banamine, Equioxx) are often used to help control pain. Isoxsuprine is commonly used also; it dilates blood vessels increasing blood flow to the bone. Pentoxifylline is also used and helps blood flow more easily through the feet. The usefulness of Isoxsuprine and Pentoxifylline with navicular syndrome remains debatable. Navicular bursa injections are also commonly used. This involves placing corticosteroids and hyaluronic acid into the bursa to help decrease inflammation. This is a "clean" procedure and should be done in a clean barn or hospital setting. Coffin joints injections are not as efficacious, but some horses do show mild improvement. Tildren is the newest treatment option for navicular syndrome. This is given intravenously over an hour and helps to slow down bone resorption. In cases that do not respond to the previously mentioned treatment options, a neurectomy (resect a portion of nerve innervating the heel) is often performed.
Prognosis: The prognosis of these horses is variable. It depends on the cause of their heel pain and the duration of pain. Proper shoeing/trimming and management will often help to reduce the pain of many horses and extend their athletic career.
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