Navicular disease is a degenerative condition affecting structures deep inside a horse’s front feet, causing chronic forelimb lameness. Once thought to involve only a single small bone, it’s now understood as a complex syndrome that can damage bone, soft tissue, and the fluid-filled cushion between them. Most veterinarians today use the term “navicular syndrome” because the problem rarely starts and ends with the bone alone.
The Navicular Apparatus
The navicular bone is a small, boat-shaped bone that sits behind the coffin bone at the back of the hoof. Its primary job is to act as a pulley: the deep digital flexor tendon (a thick cord running down the back of the leg) wraps around the navicular bone before attaching to the coffin bone. Every time the horse takes a step, the tendon presses against the bone, and the bone redirects that force to flex the foot.
A small fluid-filled sac called the navicular bursa sits between the tendon and the bone, reducing friction as the tendon slides over the bone’s surface during movement. Surrounding this core are collateral ligaments, a supportive ligament on the underside, cartilage, and the digital cushion. Together, these structures form what researchers call the navicular apparatus, or navicular enthesis organ. Damage to any one of these components can produce the lameness pattern known as navicular syndrome.
What Goes Wrong
The disease begins when abnormal mechanical forces are repeatedly applied to the navicular region. In many horses, faulty hoof conformation causes the deep digital flexor tendon to press against the back of the navicular bone with more force than the bone can tolerate. This sustained, non-physiologic pressure triggers the bone to remodel itself in an attempt to adapt.
That remodeling process creates its own problems. Increased blood flow and swelling develop inside the bone’s marrow cavity. Over time, the swollen tissue is replaced by scar-like fibrous tissue that compresses the veins draining blood from the bone. The result is a cycle of rising pressure inside the bone, restricted blood flow, and pain. Meanwhile, the cartilage on the bone’s flexor surface wears thin, the tendon itself can develop tears or adhesions, and the bursa may become inflamed. The condition is progressive, meaning it tends to worsen without intervention.
Which Horses Are Most at Risk
Navicular syndrome overwhelmingly affects the front feet, where horses carry roughly 60% of their body weight. It most commonly appears in middle-aged riding horses, typically between ages 7 and 14. Quarter Horses, Thoroughbreds, and Warmbloods seem particularly susceptible, likely due to a combination of body type and the demands placed on them.
Hoof conformation plays a major role. Horses with a long-toe, low-heel foot shape experience greater leverage forces on the navicular region with each stride. Upright, boxy feet with small frogs can also be problematic because the digital cushion beneath the navicular bone may not absorb shock effectively. Irregular or infrequent trimming that allows the toes to grow long shifts the breakover point forward, increasing strain on the deep digital flexor tendon and compressing the navicular bone more forcefully. Horses working primarily on hard surfaces accumulate more concussive damage over time.
Signs of Navicular Syndrome
The hallmark sign is a gradual onset of forelimb lameness that tends to be intermittent at first. Horses often land toe-first rather than heel-first, trying to avoid loading the painful back portion of the foot. This shortened, shuffling stride is sometimes called the “navicular shuffle.” Because both front feet are usually affected to some degree, the lameness can be subtle and bilateral, making the horse look stiff or short-strided rather than obviously lame on one leg.
You may notice your horse shifting weight from one front foot to the other while standing, pointing a front foot forward to unload the heel, or showing reluctance to work on hard ground or tight circles. Lameness often improves with rest and returns with exercise. On a circle, the horse typically looks worse when the more affected limb is on the inside, where tighter turns increase pressure on the navicular apparatus.
How It’s Diagnosed
Diagnosis involves a combination of a lameness exam, nerve blocks, and imaging. After watching the horse move and identifying the affected limb, the veterinarian uses diagnostic nerve blocks to pinpoint where the pain is coming from. A small amount of local anesthetic is injected around the palmar digital nerves, just above the heel bulbs, to numb the back of the foot. Horses with navicular pain typically show dramatic improvement in gait once both front feet are blocked.
To narrow the diagnosis further, anesthetic can be injected directly into the navicular bursa or the coffin joint. A positive response to bursal anesthesia strongly suggests pathology of the navicular bone, bursa, or supporting ligaments. A negative response to both the coffin joint and navicular bursa injections makes navicular syndrome unlikely, helping rule it out.
Imaging comes next. Standard X-rays can reveal bony changes like altered shape of the synovial fossae (small channels in the bone), increased density in the marrow, and cyst formation. However, X-rays miss soft tissue damage entirely. MRI is far more sensitive, capable of detecting tears in the deep digital flexor tendon, ligament damage, and marrow edema that conventional X-rays cannot show. CT scans also surpass traditional radiography because of their ability to produce cross-sectional images. For this reason, MRI has become the gold standard for evaluating the full scope of navicular disease.
Treatment Options
Corrective Shoeing
Therapeutic farriery is the foundation of navicular management. The goal is to reduce strain on the deep digital flexor tendon and ease pressure on the navicular bone. Common approaches include shortening the toe to move the breakover point back (making it easier for the horse to roll over the front of the hoof), applying a slight heel wedge to reduce tension on the tendon, and using egg bar shoes that extend behind the heel to increase the foot’s ground contact area. Rolled or rockered toes serve a similar purpose to a shortened toe by helping the foot break over more easily.
Egg bar shoes were once considered a go-to solution, but they come with trade-offs. While they distribute load across a larger area, the backward extension of the shoe can act as a lever, potentially increasing force on the very region you’re trying to protect. Your farrier and veterinarian should work together to find the combination that produces the best gait improvement for your individual horse, since no single shoeing prescription works for every case.
Medical Management
Anti-inflammatory medications help control pain and keep affected horses comfortable. Corticosteroid injections into the coffin joint or navicular bursa can provide targeted relief, and joint-supporting compounds like glycosaminoglycans may be injected into the joint, bursa, or tendon sheath to support cartilage health.
Two FDA-approved bisphosphonate drugs, Tildren and Osphos, are specifically labeled to control the clinical signs of navicular syndrome. These medications work by slowing down the excessive bone resorption that drives the disease cycle. It can take up to two months to see maximum improvement after treatment. For horses that respond well and maintain improvement for six months or longer, retreatment is only needed when signs return. Horses that respond but lose improvement before six months may be retreated at three- to six-month intervals.
Surgery
When medical management fails, surgical options exist. The most common is palmar digital neurectomy, sometimes called “nerving,” which cuts the nerves supplying sensation to the back of the foot. This doesn’t treat the disease itself but eliminates the horse’s ability to feel pain in the affected area.
Neurectomy can improve or resolve lameness in horses that haven’t responded to other therapies. However, in a study of 50 horses that underwent the procedure, 36% developed post-operative complications including painful nerve regrowth (neuromas), residual lameness, or early return of lameness. Horses with certain types of deep digital flexor tendon tears, specifically core or linear lesions, had significantly shorter periods of pain relief and are generally considered poor candidates for the procedure. The loss of sensation also carries an inherent risk: the horse can no longer feel injuries in the back of the foot, so owners must be vigilant about checking for wounds, abscesses, or worsening structural damage.
A less invasive surgical option is navicular bursoscopy, in which a small camera is inserted into the navicular bursa. This allows the surgeon to clean up tendon tears on the bone’s surface, smooth eroded cartilage, and break down adhesions within the bursa.
Long-Term Outlook
Navicular syndrome is manageable but not curable. The degenerative changes to bone and soft tissue cannot be reversed, so the goal shifts to slowing progression, controlling pain, and maintaining the horse’s quality of life. Many horses continue in work for years with a combination of corrective shoeing, periodic medical treatment, and thoughtful management. Keeping horses on softer footing, maintaining a consistent trimming and shoeing schedule every four to six weeks, and avoiding excessive work on hard ground all help reduce the cumulative stress on the navicular apparatus.
Horses with mild to moderate disease and good hoof care often do well at moderate levels of work. Those with advanced tendon damage or significant bone deterioration have a less favorable outlook, particularly if they stop responding to bisphosphonate therapy or corrective shoeing. Early detection through MRI gives the best chance of catching soft tissue changes before they become severe, which is why persistent, low-grade bilateral forelimb lameness in a middle-aged horse should always prompt a thorough foot evaluation.