Technical information for veterinarians
Navicular syndrome in horses
What is navicular syndrome?
Navicular syndrome (podotrochlosis, podotrochlitis), sometimes referred to as Caudal Heel Syndrome, is one of the most common causes of chronic forelimb lameness. Navicular syndrome occurs almost exclusively in the front feet and usually affects both sides.
In the horse, the navicular bone is located directly behind the coffin bone and is held in place by tendons and ligaments.
The navicular bone has two functions:
- To protect the joint and tendons from pressure and concussion (the navicular bone acts as a pulley on the deep digital flexor tendon, which takes some of the stress off the coffin bone).
- To act as a valve for blood flow to the coffin bone and corium inside the hoof.
If the hooves are not properly cared for, the navicular bone becomes immobile, resulting in poor blood flow within the hoof. Damage and/or breakdown of the navicular bone and related connective tissue structures results in pain and a visible stumbling gait.
Etiology of navicular syndrome
Navicular disease consists of primary pathological changes within the bone, sometimes associated with degeneration of the fibrocartilage of the navicular bone and the deep flexor tendon within the confines of the navicular bursa. These changes also include the trabecular structure of the bone including the sesamoidal canals naturally present especially in the distal end of the navicular bone.
To compensate for the natural process of bone degeneration, the bone regenerates itself. When the process of regeneration becomes slower than the process of degeneration, rough areas develop on the navicular bone. These tend to catch on the deep flexor tendon when the horse walks.
Contributing factors for navicular syndrome include the following:
Breed and Conformation
Certain breeds of horses are more likely to develop navicular problems. These include breeds with feet that are small related to body size. The support structures in the hoof are designed by nature to absorb shock and carry the horse; the smaller the hoof in relation to the horse’s size, the greater the shock to the navicular bone. Breeders often select horses for their small feet, believing them to be more attractive.
A more upright pastern may also predispose certain horses to the development of navicular syndrome.
Quarter horses have a higher incidence of navicular syndrome than other breeds.
The more pressure that is applied to the navicular bone from the deep flexor tendon, the higher the probability that the horse will suffer from navicular disease. Increased pressure is caused by overweight horses and horses with small feet (proportionate to the size of their bodies).
A horse’s activity level may play a role in the development of navicular syndrome. This is particularly true when the horse is utilized in stressful athletic activities for which he is not suited. Horses that undergo a fair amount of percussion on the forefeet are inclined to experience navicular syndrome. Barrel racing, for example, puts a lot of stress on the horse’s foot and may lead to navicular problems.
Reduced blood supply
Reduced blood supply to the navicular area may initiate or perpetuate navicular disease.
Younger horses are affected more often. Horses that have definite symptoms of navicular problems are usually between the ages of 3 and sixteen years.
At least one study shows a genetic predisposition toward the development of navicular syndrome. This may relate to the conformation of the foot and the natural angle of the pastern. Some veterinarians believe that the more upright the pastern, the more likely the horse is to develop navicular syndrome.
Improper shoeing can cause a lot of joint and muscle problems and is a significant factor in the progression of degenerative disease. Corrective shoeing is something that is manageable with the help of an experienced and well-respected farrier.
Horses likely to develop navicular syndrome
Horses that are at high risk for developing navicular problems are usually confined or stall-kept, and have strong physical demands placed on them.
Quarter horses are particularly prone to the disease but it is unknown whether this is due to some hereditary factor or is related to conformation. The more pressure that is applied to the navicular bone from the deep flexor tendon, the more likely the horse will suffer from navicular disease.
Overweight horses, and horses with small feet (proportionally to the size of their bodies) are more likely to develop navicular problems.
Quarter horses and thoroughbreds have proportionally small feet and high body weight, which may explain the tendency towards development of navicular disease in these breeds.
Symptoms/diagnosis of navicular syndrome
Navicular syndrome causes a gradual and progressive increase in lameness of the front legs. Due to the gradual nature of onset, navicular problems are difficult to detect until the condition is advanced.
While walking, the horse with navicular syndrome tends to place its weight on the toe to avoid placing pressure on the heel area, which contains the inflamed navicular bone and bursa. Since the horse will not place weight on the heel, it takes longer to stop the stride.
While standing, a horse with navicular syndrome tends to shift its weight continuously to relieve pressure and pain within the heel. A horse with navicular syndrome is often lame after work; however, the lameness may disappear with rest. Due to comparably poor circulation in the feet of many horses with navicular syndrome, the heels and adjacent hooves may become smaller and contract.
X-rays do not always detect early signs of navicular disease since the soft tissues are usually the first problem areas.
Other navicular syndrome signs to watch for include:
- Shortening of the stride
- A continual shifting of body weight when resting
- A stumbling gait
- Slight unevenness on turns
- Reluctance to go forward properly or lengthen the stride
- Pointing – the horse will stand at rest with one leg extended, the weight resting on the toe
- When the foot is pressure tested, the horse will usually indicate heel pain
- General irritability
Dressage horses with navicular syndrome may have trouble coming onto the bit or may refuse to perform a maneuver with which they have demonstrated ease in the past.
Racehorses with navicular syndrome may quit during the race, slow down noticeably at the 3/4 pole or exhibit loss of form.
Jumpers with navicular syndrome may refuse or take down the rails.
Event horses with navicular syndrome may exhibit poor recovery (including a prolonged rapid heart rate, respiratory rate and temperature) from the strenuous phases of the event or may have trouble making times.
Pleasure horses with navicular syndrome may stumble or show signs of irritation (tail swishing, head bobbing).
Endurance horses with navicular syndrome, like event horses, may show poor recovery or inability to finish rides.
If both feet are affected by navicular syndrome, lameness will be less obvious. It will be more easily detected if the horse is turned in a short circle, when he may try to rotate on the foot rather than picking it up to take a step.
Navicular disease may also be diagnosed with hoof testers. Placing one tong on the outside wall and the other on the sole or frog will cause pain for a horse with navicular syndrome. The placement of both tongs across the outside of the heel will also cause discomfort.
Nerve blocks are useful in diagnosing navicular syndrome. A local anesthetic such as lidocaine or carbocaine is used on different nerves until the horse is sound when trotted out. If the horse appears sound after the nerve that serves the navicular bone, is may be assumed that navicular disease is causing the lameness.
When navicular syndrome is suspected, X-rays are normally taken to make sure the horse definitely has the syndrome and not, for example, a fractured bone or abscess. X-rays will reveal the degree of deterioration in the navicular bone. It may be difficult to obtain good X-rays that will show the problem, especially during the initial stages. Unfortunately, only 50 percent of cases of navicular disease can be diagnosed from X-rays. Since X-rays are expensive, most diagnoses are made through a process of elimination.
A combination of nerve blocks and X-rays is the most commonly used diagnostic technique.
Treatment options for Navicular syndrome
The treatments of navicular syndrome vary widely, since problems in the navicular area have several causes.
Treating a horse with navicular disease remains a controversial issue. The treatment chosen depends on the demands put upon the horse and the severity of the condition.
Navicular syndrome will not directly shorten the length of the life of a horse. There are many ways to relieve the pain of navicular disease so that the horse will be able to continue on as normal. These include:
TRIMMING THE FEET
Currently, the most effective treatment for navicular syndrome appears to be good foot care. Numerous styles of shoes have been developed to help relieve pressure of the deep flexor tendon, therefore relieving pain in a horse with the condition. Horses showing signs of navicular disease should be shod more frequently than other horses (every six to eight weeks). Each horse should be trimmed according to the particular conformation that needs correction.
Raise the horse’s heel
One recommendation for shoeing a horse with navicular syndrome is to raise the heel. By raising the heel, less pressure is exerted by the deep flexor tendon when the horse lifts his foot to walk. Although raising the heel can relieve the pain of navicular disease, the rest of the foot is strained due to the new, steeper angle. Wedge shoes and wedge pads will both raise the horse’s heel.
Rounding the toe
Another recommendation for shoeing a horse with navicular syndrome is to round the toe. By doing this, pressure is taken away from the deep flexor tendon as the horse attempts to walk. The shoe allows the horse to “roll” or “rock” up off of the heels instead of having to forcefully pick up the foot. A rolled toe shoe or rocker toe shoe allows for “rocking” or “rolling.”
Setting the shoe under
Yet another common practice in shoeing a horse with navicular syndrome is “setting the shoe under.” This entails leaving hoof beyond the edge of the shoe, and then rounding it, so that it acts as a rocker. When the hoof is rounded it takes less effort for the horse to pick up their foot and move.
Medications are frequently prescribed for horses with navicular syndrome to help relieve pain temporarily. Many oral and injectable drugs are available for temporary use. Prolonged use of many of these drugs can cause damage to the horse and their use may be illegal in competitions.
Isoxuprine HcL (Circulon®) For mild to moderate navicular disease you may prescribe isoxuprine. Isoxuprine HCl is the most common drug used to increase the circulation to the podotrochlea.
Isoxuprine does not decrease damage to the joint and is usually only successful in the early stages of navicular syndrome. Isoxuprine therapy is a long course of regular drug therapy which can become expensive and time-consuming.
Warfarin is sometimes recommended for mild to moderate navicular disease.
Like isoxuprine, warfarin is a permanent course of therapy. Vitamin K should also be employed with warfarin to enhance normal clotting. The horse must be watched carefully for bleeding problems.
Non-steroidal anti-inflammatory drugs (NSAIDs)
NSAIDs help reduce the pain and swelling of the joints and decrease stiffness. When taken at a low dose, NSAIDs reduce pain; when taken at a higher dose, NSAIDs can also reduce inflammation.
NSAIDs do not prevent joint damage and when used long-term, may accelerate joint breakdown. Taking more than one NSAID at a time increases the possibility of severe side effects such as ulcers and bleeding. NSAIDS affect normal blood clotting and therefore may interact with other blood-thinning medications, such as warfarin.
Cortisone is a corticosteroid that reduces inflammation and swelling. For severe pain and inflammation, a corticosteroid, such as cortisone, may be injected directly into the affected joint. Although corticosteroids closely resemble cortisol, they exert a much more powerful anti-inflammatory effect. An injection can provide almost immediate relief for a tender, swollen and inflamed joint.
Visco-supplementation is the process of injecting a gel-like substance into the joint. This substance lubricates the cartilage, reducing pain and improving flexibility. Visco-supplementation decreases friction within the joint, thus reducing pain and allowing greater mobility. This method of treatment requires ongoing injections as benefits are only temporary. Substances used in visco-supplementation include hyaluronic acid, or HA (Legend®, Hylartin® and Synacid®), and poly-sulfated glycosaminoglycans (PSGAGS) such as Adequan®
If surgery is required
Surgery may be the only option for horses with long-standing navicular syndrome.
Neurectomy is a drastic treatment, usually reserved for long-term cases of navicular disease. A small piece of the two nerves that penetrate the navicular area is cut below the fetlock. This numbs the entire foot.
Problems resulting from this surgery involve stumbling due to the fact the horse has lost sensation in the foot and does not know where it has been placed. Since equine health problems involve the foot, and the horse will be lacking sensation in the foot, horses that have undergone neurectomy should be closely monitored for hoof and leg problems.
Sometimes, the severed nerve may grow back, but can be cut as many times as necessary to keep the horse pain-free.
A new surgical treatment that involves cutting the collateral sesamiodean ligaments (CSL) results in long-term improvement for some horses. The surgical approach is made just proximal to the collateral cartilages, just cranial to the digital vein. A 2-cm incision is made, the vein is retracted palmarly, and the CSL can be located as it courses proximally and dorsally over the short pastern bone. A hemostat is used to dissect around the ligament and then transection is performed. Closure is standard. The horse is allowed to rest for 2 weeks before being returned to work.
Natural options for Navicular Syndrome in horses
Recovery®EQ with Nutricol®, is an elite proprietary performance and wellness supplement for horses that enhances quality of life.Recovery®EQ improves healing by increasing circulation of nutrients to affected cells and extracellular structures, halting tissue damage and decreasing inflammation. It may be used on its own or in combination with prescribed medications. Ask your veterinarian how Recovery®EQ can help your horse.
Review in the prestigious Horse Journal in October and December 2003
Recovery®EQ rated as “Best Performer Overall” as a pain-relieving supplement for joint pain, back pain and tendonitis – comparison of natural joint care supplements.
Review in the prestigious Horse Journal inJune 2006:
“You get what you pay for” – Horse Journal quote about Recovery®EQ used as a performance enhancing supplement – comparison of natural performance enhancing supplements
For more information on helping your horse stay healthy, please see Tips for a Healthier Horse