Navicular disease is a slowly progressive degenrative condition of the navicular bone, causing chronic degeneration of the navicular bone in which there is damage to its flexor surface and the overlying flexor tendon in the front feet.
There may be accompanying navicular bursitis (inflammation of the fluid sac around the navicular bone) and osteophyte formation (bony growths). Navicular disease usually causes intermittent lameness and toe pointing when the horse is standing; unfortunately the disease cannot be cured, but a horse suffering from the disease can be treated to relieve any associated pain or discomfort.
Navicular disease should not be confused with navicular syndrome; this is any one of a number of conditions that can cause pain referable to the back of the hoof or navicular area. This can include damage to the navicular tendons and ligaments, inflammation of the navicular bursa and a number of other things.
The navicular bone is located directly behind the coffin bone, held in-between the short pastern and coffin bone by tendons and ligaments.
The navicular bone has two main functions:
- To protect the joint and tendons from pressure and concussion.
- To act as a valve for blood flow to the coffin bone and corium in the hoof.
How is navicular disease diagnosed?
Horses with navicular disease will show the following signs:
- A short, choppy foreleg lameness that often shifts from one foot to the other. Affected horses may stumble or resist lengthening their stride because they are reluctant to land and load weight on the heels of their front feet.
- Sole and toe bruising:
- This is a result of the inability of the horse to use the cushion of the frog and heels when landing.
Possible causes include:
- Repetitive trauma to the heels and navicular area.
- Interruption of circulation to and from the navicular bone.
- Short, upright pastern conformation.
- Poor shoeing with long toes and underrun heels.
How is navicular disease treated?
Treatments involved include corrective shoeing - the use of elevated heel shoes may be necessary.
Eggbar shoes may also be used. Although corrective shoeing is a popular choice for treatment of navicular disease, a farrier can't cure or correct navicular disease, he can only relieve the symptoms to a certain degree.
Your horse may also need to be administered vasodilator drugs, these will help improve the blood supply to the navicular bone. Horses with navicular disease can be kept sound with good shoeing and with vasodilator drugs. As Navicular disease is a bone disease then so called bone remodelling agents (E.g. Tildren or Osphos) can be used which are given by injection. Injection of the navicular or coffin joints with sodium hyaluronate (HA) or corticosteroids has also proven to be very effective for some horses, although long-term soundness is not guaranteed with any of these treatments.
Neurectomy (de-nerving) may be necessary for selected chronic cases. Neurectomy involves sectioning of the nerve supplying the navicular bone, hence providing permanent pain relief.