Navicular in horses: tell-tale symptoms to look out for
The navicular bursa is a sac filled with lubricating synovial fluid positioned at the back of the bone to cushion the deep digital flexor tendon as it passes over the navicular bone
Historically, navicular was attributed to interruption of the blood supply to the navicular bone: this is ‘the vascular theory’. This has gone out of favour as a major factor in navicular syndrome but treatments geared towards restoring the blood flow do have some effect, so opinion is still divided.
The navicular bone takes a lot of biomechanical strain when the horse moves. As the deep digital flexor muscle contracts, the tendon tightens and pushes on the navicular bone. To help prevent damage to the tendon or navicular bone, a thick layer of fibrous cartilage protects the bone, and this may be worn down in cases of navicular syndrome.
Which horses are most at risk of navicular symptoms?
To make some generalisations, navicular is more often found in horses with a certain foot conformation: overlong toes and collapsed heels. There is believed to be a genetic component as navicular syndrome is more common in certain breeds such as warmbloods, thoroughbreds and quarter horses. It rarely affects ponies. A susceptible conformation subjected to repetitive concussion can lead to a degenerative processs within the foot.
The average age for a horse to develop signs of navicular disease is between seven and 11 years. This perhaps reflects the degenerative nature of the problem caused by wear and tear. However, I know that it can occasionally be seen in horses as young as three.
How is navicular diagnosed?
Diagnostic techniques taken from human medicine have been adapted for horses. This has taken the diagnosis of navicular syndrome to a new dimension. Magnetic resonance imaging (MRI) and Computed Tomography (CT) allow vets to take a closer, detailed look at all the structures in the hoof: bone, cartilage, tendons and ligaments. This means that we as vets are able to diagnose soft-tissue injuries previously unseen on X-ray.
MRI scanning is restricted to referral hospitals. Conditions that once upon a time may have been put down to navicular can now be more accurately diagnosed, such as fraying of the deep digital flexor tendon within the hoof or damage to the supporting ligaments of the navicular bone. These ways of viewing the foot are very useful but also expensive (in excess of £1,000). Some insurance companies don’t cover their cost fully, so it’s worth bearing this in mind if you choose to go down this route.
Which horses are most at risk of navicular symptoms?
To make some generalisations, navicular is more often found in horses with a certain foot conformation: overlong toes and collapsed heels. There is believed to be a genetic component as navicular syndrome is more common in certain breeds such as warmbloods, thoroughbreds and quarter horses. It rarely affects ponies. A susceptible conformation subjected to repetitive concussion can lead to a degenerative processs within the foot.
The average age for a horse to develop signs of navicular disease is between seven and 11 years. This perhaps reflects the degenerative nature of the problem caused by wear and tear. However, I know that it can occasionally be seen in horses as young as three.
How is navicular diagnosed?
Diagnostic techniques taken from human medicine have been adapted for horses. This has taken the diagnosis of navicular syndrome to a new dimension. Magnetic resonance imaging (MRI) and Computed Tomography (CT) allow vets to take a closer, detailed look at all the structures in the hoof: bone, cartilage, tendons and ligaments. This means that we as vets are able to diagnose soft-tissue injuries previously unseen on X-ray.
MRI scanning is restricted to referral hospitals. Conditions that once upon a time may have been put down to navicular can now be more accurately diagnosed, such as fraying of the deep digital flexor tendon within the hoof or damage to the supporting ligaments of the navicular bone. These ways of viewing the foot are very useful but also expensive (in excess of £1,000). Some insurance companies don’t cover their cost fully, so it’s worth bearing this in mind if you choose to go down this route.
How to prevent navicular and its symptoms
It can be hard to see how you can possibly prevent a condition like navicular developing when so many factors contribute to it. However, some simple rules do apply.
