Navicular disease in horses is usually diagnosed only when an obvious lameness is present. However, a number of clinical signs are evident to the careful observer some 18 to 24 months before the onset of lameness. I believe that, with intelligent analysis of the signs that are apparent in pre-navicular syndrome and with the help of regular shoeing to restore the correct mechanical balance of the limbs and feet of affected horses, the development of pre-navicular syndrome can be prevented and a permanent and effective cure can be obtained.
Farriers and veterinary surgeons should recognize the signs of change in the horse’s behavior, gait, feet, and shoe-wear to affect an early diagnosis of a developing syndrome. This clinical condition will, if left untreated, develop into navicular disease.
Navicular disease is a chronic progressive forelimb lameness and is the final stage of a clinical syndrome. The majority of horses who exhibit signs within the navicular syndrome seem to share one factor, that of anterior-posterior hoof-pastern imbalance (broken-back axis), which may or may not be complicated by medio-lateral (side-to-side) hoof imbalance.
Under such conditions, greater weight is borne by the back parts of the foot, rather than distributed over the entire ground surface of the wall and bars, as it should be. The direct result is that the heels collapse under excessive pressure and become under-run, thus failing to support one foot. Once this process of collapse has begun, it becomes self-perpetuating, as the angle of weight-bearing becomes greater and greater.
In consequence, structures within the hoof - the lateral cartilages, digital cushion, navicular bone, deep flexor tendon, blood vessels, and nerves - are all subjected to abnormal stresses and pressures.
Once the disease has progressed to the stage of producing structural changes in the bone, navicular suspensory ligaments, or deep flexor tendon, it must be considered incurable.
1. Farriery Causes
2. Management and Environment Causes
3. Conformation Causes
Diagnostic Clinical Signs
1. Behaviour Changes
2. Gait Causes
3. Signs Evident in Motion
4. Signs Evident at Rest
The farrier is in the ideal position to observe changes in a horse’s feet, far more so than the owner or veterinary surgeon, and especially if the horse is shod in a regular routine. Dramatic change can occur in the shape of a hoof in a six week interval; other changes can be long-term and insidious.
The front feet of navicular and prenavicular horses fall into three distinct categories:
a) Flat, squashed feet
b) Upright, boxy feet
c) One foot of each type
Successful treatment of Navicular Syndrome is dependent on suitable mechanical correction of the foot. Three main priorities in all cases must be:
1. The restoration of correct hoof-pastern axis
2. The restoration of correct medial-lateral balance
3. Full support of the caudal parts of the foot through shoeing
There appear to be two distinct and separate theories about corrective farriery for the treatment of navicular disease. A 1982 study claimed 58% success (permanent relief of signs) with the use of the egg bar shoe without drug therapy. Meanwhile, a 1983 study recommended the raised-heel, rolled-toe shoe.
Effective diagnosis and treatment of navicular discomfort, pain, and impending overt lameness (the prenavicular syndrome) may be instituted long before radiographic evidence can confirm a diagnosis of navicular disease.
The onset of navicular disease is gradual and insidious. However, it is possible to arrest it and even reverse its effects as long as the root mechanical causes are corrected through shoeing.
Read the full research report on Pre-Navicular Syndrome here .