Navicular disease in horses is a progressive degenerative condition involving the navicular bone (which is located behind the coffin bone in the hoof), the bursa and the deep digital flexor tendon (DDFT) of one or, more commonly, both front feet.
Navicular is not actually a ‘disease’, it is a syndrome of abnormalities. Although the term – along with ‘navicular syndrome’ or ‘palmar foot pain’ as it’s sometimes known – was once widely used as a generic diagnosis of heel pain, thanks to advances in technology vets now use the term ‘navicular disease’ to specifically refer to changes within the navicular bone structure itself, identified by MRI scanning.
Recognising navicular disease
Navicular disease typically affects both front hooves, although one foot is often worse than the other, so your horse may initially appear lame on one front leg. However, on the lunge the horse may show lameness on the inside leg in both directions. You may also notice that he lands with the toe of the hoof first, ahead of the heel. In addition, navicular generally worsens with hard work and lessens with rest. While none of these symptoms add up to a definitive diagnosis of navicular, if observed, they may point you in that direction.
If you suspect your horse may be suffering from navicular disease, you should contact your vet. They are likely to perform flexion tests and nerve block the affected area to see if this reduces the lameness. The final step is to X-ray or MRI scan the caudal heel area; your vet will be looking for pathology that may include cyst-like lesions within the navicular bone, degeneration of the flexor surface of the navicular bone, and mineralisation or calcification of the ligaments associated with the navicular bone. Typically, the clinical examination, nerve-blocking and radiographs should give enough data for a firm diagnosis.
Causes of navicular disease
As it’s not a disease as such, there’s no one particular cause of the condition. Inflammation or injury of the supporting tissue, or problems within the bone itself, can lead to lameness. As it’s more prevalent in competition horses, it’s thought that excessive stress may lead to degeneration of the navicular bone in some horses.
Other possible contributing factors include:
Breed. Although it’s found in all breeds of horses, it’s most typically diagnosed in quarter horses, thoroughbreds and warmbloods
Conformation. Underrun heels, sheared heels, contracted heels, mismatched hoof angles, and disproportionally small feet may all be contributing factors in a predisposition towards navicular
Age. Affected horses are usually between the ages of 7 and 14.
Treatment for navicular
The treatment for navicular is as varied as the possible causes so you may need to try various options to see how your horse responds. As it’s a chronic condition, it’s unlikely your horse will make a full recovery, so you need to look ways to manage the condition rather than curing it.
If it’s thought that foot conformation may be a factor, therapeutic shoeing may help. One school of thought is that it’s best to remove shoes to improve the blood flow to the feet, but others choose corrective shoeing, using a shoe that lifts and supports the heel. Your vet and farrier can advise you on the best course of action for your horse.
Medication is usually in the form of an anti-inflammatory drug such as phenylbutazone (Bute). Many horses respond well to a combination of medication and effective farriery.
As navicular worsens with hard exercise, you may also need to look at reducing your horse’s workload.
Surgery is sometimes considered as a last resort; known as ‘nerving’ or ‘denerving,’ the palmar digital nerves are severed, so the horse loses sensation in the heel. As with any surgery, this is not without risk and may only mask the issue, causing more serious problems in the long term.