E544
Navicular Disease
(Podotrochleosis)

Introduction: Navicular disease, one of the most common causes of lameness in horses, is most often found in Quarter horses and Thoroughbreds. Males seem to be at the greatest risk, with some evidence indicating that the problem can be inherited. Animals that are required to perform high impact workouts and competitions (racing, calf-roping, cutting, barrels, etc.) are at an increased risk of developing the disease. To completely understand this disease, it is essential to be familiar with the anatomy and common terms that are associated with navicular problems. See A30 for the exact location of the navicular bone and the associated structures.

Causes: Many internal and external factors can cause a horse to have navicular problems. The following list names just a few of the most common:

  1. Conformation problems - These horses often have small feet and are "upright" in the pastern. "Upright" in the pastern means that the pastern region does not have the normal slope from the fetlock to the coronary band. The slope is too steep and does not match the slope of the hoof wall. 

  1. Repeated stress to the navicular bone and surrounding structures.

  2. This commonly happens in the hard working and/or performance horse.
  3. Physical injury - This can be as simple as a puncture wound in the navicular area.
  4. Improper shoeing or trimming.

The above conditions can cause increased pressure and wear to the navicular bone, the navicular bursa, and the deep digital flexor tendon. This continued trauma causes changes to the bony structure of the navicular bone and cartilage. The above four problems may also cause the vessels that supply blood to the navicular bone to fail to deliver an adequate blood supply to the region. This also causes abnormal changes in the navicular bone. All of this changing and remodeling to the navicular bone can cause pain and lameness in the horse.

Clinical Signs: Typically, a horse suffering from navicular disease most often exhibits lameness in the front limbs. This lameness is intensified after hard work. These horses may be lame in one, two, three, or all four limbs. No matter which foot is involved, the horse will avoid bearing weight on the heel portion of the foot. This is understandable, since the navicular bone is located in the back third of the foot (see A30). Many of the navicular horses show increased wear on the toe, and may even have a bruised area in the toe region of the sole.

Diagnosis: A diagnosis is made using many different techniques and diagnostics. The first step in diagnosing a horse with navicular disease involves performing a thorough lameness examination. This includes observing the horse in motion, using hoof testers (see B885 figures 6-9), and blocking nerves to certain regions of the foot. Once the disease has progressed to the point that changes have occurred on the navicular bone, radiographs can be utilized to aid in the diagnosis.

Treatment: There are many different approaches to treating a horse with navicular disease. One or all of the following may be necessary, depending on the given situation:

  1. Corrective shoeing - The concept behind corrective shoeing is taking the pressure and weight off the heel and navicular region of the foot. This is accomplished by shortening the toe and elevating the heels. Many farriers use special shoes such as an egg bar and/or a "rocker/rolled" toe shoe. The egg bar type of shoe protects the navicular area and causes the weight of the animal to be distributed more evenly around the foot. The "rolled" toe shoes cause the foot to break over more quickly, thus creating less tension on the deep digital flexor tendon and navicular bone. Many different types of wedge and rim pads can be used to help elevate the heel and absorb some of the concussion.

  2. Medications:
  1. Anti-inflammatory agents - These include bute, Banamine, and Ketoprofen. In some situations, steroids may be recommended.
  2. Polysulfated glycosaminoglycans (Glyco-Flex and Adequan) to reduce cartilage degeneration.
  3. Isoxsuprine hydrochloride to improve blood flow to the navicular bone.
  1. Surgery
  1. Navicular suspensory desmotomy - This procedure cuts two of the ligaments that connect the navicular bone to the coffin joint. This reduces the stress that is placed on the navicular bone during weight bearing.
  2. Digital nerve neurectomy - Because of the risks this procedure poses to horse and rider, this should be reserved as a last resort. This surgery involves severing the nerves that provide sensation to the back portion of the foot. This can result in immediate pain relief for the horse. However, because the horse has no feeling in the back portion of the foot, some animals may not be able to place their feet properly, thus resulting in a greater tendency to stumble. This complication should be taken into consideration if the horse is to be used by inexperienced riders. Because of this lack of feeling, some horses may rupture the deep flexor tendon when abnormally high amounts of strain are placed on the tendon.

Prevention: This problem is often difficult to prevent. However, proper shoeing of a horse that has had problems with navicular disease in the past, can help prevent additional problems. Weight control is also beneficial, especially in horses that are heavy-chested and carrying 60% or more of their weight on their front feet. Horses that have large bodies, small feet, poor conformation, and navicular problems in their lineage, should be considered at a greater risk of developing this disease.