Jeske Noordergraaf, VMD

August 2006

Navicular is a term that scares many horse owners as it could mean that your horse will be lame from now on.  The first horse that I owned back when I was in high school was diagnosed with this a few years after I sold him.  Thinking back to when I did own him, it makes sense as he was occasionally lame.  I had a veterinarian look at him on several occasions but he was sound again on those days after being rested and so no diagnosis was made.    

The history with these horses is that they are intermittently lame; it comes and goes and it always seems that they are lame on the day you want to go to a horse show.  It may be hard to determine which leg the horse is lame on as the lameness can shift from side to side.  These horses may also stand pointing one foot and they may stumble more than they should when they are being ridden.  There does to be a hereditary predisposition which is probably related to conformation.  Poor conformation, improper or irregular shoeing, exercise on hard surfaces and hoof imbalance are all factors which can lead or add to the lameness.

Several structures in the hoof are involved with this disease.  These include the navicular bone (also known as the distal sesamoid), the ligaments of the bone, the bursa, which is the cushion between bones, and the deep digital flexor tendon. 

The diagnosis of navicular syndrome is based on the following signs:

• History

• Response to hoof testers placed on the frog

• Radiograph findings

• Response to nerve blocks

• New diagnostic tests including CT scans and MRI

The history usually indicates that this lameness had a gradual onset.  The horse tends to respond to hoof testers when they squeeze over the navicular bone and bursa.  The x-rays may show that the bone has either degenerative changes, such as spurs on the edges, or cones and lollipops, as we call the holes in the bone.  A local anesthetic placed around the nerve going to the navicular bone and back third of the hoof numbs that area, making the pain go away.  If the problem is in that area and the pain is gone, the horse should become sound on that leg and we may see lameness in the other front leg.  The new diagnostic tests allow great visualization of that area, but they are not routinely available yet.  Remember that not all these signs may be present but your horse could still have this diagnosis.

Navicular does not necessarily mean that your horse is unusable.  There are many treatment options which include:          

• Anti-inflammatory drugs such as phenylbutazone.

• Isoxsuprine which is a vasodilator.  It increases the blood flow to that area.

• Systemic joint therapies such as Adequan and Legend.  These help with cartilage healing and joint lubrication.

• Cosequin or another supplement which contain chondroitin, MSM, and other
   ingredients which help with joint health.

• Joint injections into the bursa or coffin joint to help with lubrication and
  decrease the inflammation or irritation present.

Keeping your horse from becoming overweight is also helpful, as there is less weight per square inch of foot.  We do not recommend breeding these horses, as there is a hereditary component. 

There is new research that measures the pressure in the navicular bone and determines if drilling holes in this bone can reduce the pressure, the pain and the lameness.  Dr. Jenner, who was at the University of Minnesota, wrote her thesis on this new technique.  Research is also being done on the deep digital flexor to determine if that is the cause of the pain.

Navicular syndrome has been a challenge for many years but does not have to end a horse’s career.  Current surgeries which are being done include a neurectomy or desmotomy.   First figure out why your horse is lame, keep up on your horse’s hoof care, (that old saying of “no hoof, no horse” is certainly true), don’t let your horse get obese, and breed responsibly.

Happy trails.