Navicular disease in horses leads to lameness due to the degeneration of the navicular bone, a small boat-shaped bone in the hoof. This degeneration affects the surrounding tissues, including the navicular bursa and deep digital flexor tendon, causing pain and subsequent lameness. The condition is progressive and can significantly impact a horse’s athletic ability and overall well-being.
What is Navicular Disease?
Navicular disease, or navicular syndrome, is a chronic degenerative condition affecting the navicular bone in horses. The navicular bone is a small bone located behind the coffin bone in the hoof. The disease is a leading cause of chronic forelimb lameness, particularly in athletic horses.
How Does Navicular Disease Cause Lameness?
Navicular disease causes lameness through a combination of factors that result from the degeneration of the navicular bone and surrounding tissues:
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Bone Degeneration: The navicular bone undergoes changes such as sclerosis (increased density), cyst formation, and erosion of the cartilage. These changes disrupt the smooth surface of the bone, leading to friction and pain.
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Inflammation: The degeneration of the navicular bone leads to inflammation in the navicular bursa, a fluid-filled sac between the navicular bone and the deep digital flexor tendon. This inflammation contributes to pain and lameness.
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Deep Digital Flexor Tendon Involvement: The deep digital flexor tendon (DDFT) runs over the navicular bone and can be affected by the changes in the bone. Rough surfaces on the navicular bone can cause wear and tear on the DDFT, leading to tendonitis and pain.
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Ligament Damage: The ligaments supporting the navicular bone can also be damaged as the disease progresses, leading to instability and further pain.
What are the Symptoms of Navicular Disease?
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Gradual Onset of Lameness: Lameness typically starts gradually and may initially be subtle.
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Bilateral Lameness: Often affects both front limbs, though one limb may be more affected than the other.
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Short, Choppy Stride: Horses may exhibit a shortened stride, particularly in the front limbs.
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Increased Heel Pain: Pain is often exacerbated when the heel is stressed or when the horse is worked on hard surfaces.
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Toe Pointing: Affected horses may stand with their toes pointed forward to alleviate pressure on the heels.
How is Navicular Disease Diagnosed?
Diagnosing navicular disease typically involves a combination of clinical examination, nerve blocks, and imaging techniques:
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Clinical Examination: A veterinarian will assess the horse’s gait and perform a lameness examination to identify the source of pain.
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Nerve Blocks: Perineural analgesia, or nerve blocks, are used to desensitize specific areas of the foot. Improvement in lameness after blocking the palmar digital nerves (which supply sensation to the heel area) suggests navicular involvement.
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Radiography (X-rays): X-rays can reveal changes in the navicular bone, such as increased density, cyst-like lesions, or changes in shape.
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Magnetic Resonance Imaging (MRI): MRI provides detailed images of the soft tissues and bone structures, allowing for a more comprehensive assessment of the navicular bone, ligaments, and tendons.
People Also Ask (PAA)
What is the prognosis for horses with navicular disease?
The prognosis for horses with navicular disease varies depending on the severity of the condition and the horse’s response to treatment. While navicular disease is progressive, many horses can remain comfortable and functional with appropriate management. Early diagnosis and intervention are crucial for improving the long-term outcome.
Can navicular disease be prevented?
While it may not be possible to prevent navicular disease entirely, certain management practices can help reduce the risk. These include maintaining proper hoof balance, providing appropriate shoeing, avoiding excessive concussion, and managing the horse’s weight. Regular veterinary check-ups can also help detect early signs of the disease.
What are the treatment options for navicular disease?
Treatment options for navicular disease aim to manage pain and slow the progression of the disease. Common treatments include corrective shoeing, pain medications (such as NSAIDs), bisphosphonates, and joint injections. In some cases, surgery may be considered.
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