Navicular syndrome in equine patients anatomy, causes, and diagnosis.
Authors: Waguespack, Hanson
Journal: Compendium (Yardley, PA)
Summary
Navicular syndrome remains one of the most prevalent causes of forelimb lameness in horses, characterised by chronic, often progressive degeneration affecting the navicular bone, bursa, deep digital flexor tendon, and surrounding soft tissue structures within the navicular apparatus. Waguespack and Hanson's review synthesises diagnostic approaches spanning clinical examination, lameness assessment, and peripheral and intraarticular anesthesia blocks, alongside multiple imaging modalities including radiography, ultrasonography, scintigraphy, thermography, computed tomography, and magnetic resonance imaging. A critical finding is that radiographic changes are neither pathognomonic for nor universally present in navicular syndrome—some affected horses show no bony changes on conventional radiographs, whilst others display changes without clinical disease—highlighting the limitations of radiography as a sole diagnostic tool. Advanced imaging, particularly MRI and CT, reveals lesions invisible on radiographs and increasingly implicates anatomical structures beyond the traditionally implicated navicular bone, bursa, and tendon, sometimes necessitating navicular bursoscopy for definitive diagnosis when other modalities remain inconclusive. For practitioners, this underscores the importance of correlating imaging findings with clinical signs rather than relying on radiographic appearances alone, and maintaining a broader perspective on potential soft tissue contributors when investigating chronic heel lameness.
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Practical Takeaways
- •Do not rely solely on radiographs to diagnose or rule out navicular syndrome; advanced imaging (MRI/CT) may be necessary when clinical signs suggest navicular disease but radiographs are inconclusive
- •Navicular syndrome diagnosis requires integration of history, physical examination, lameness evaluation, and diagnostic anesthesia alongside imaging—no single test is definitive
- •Consider structures beyond the traditional navicular complex (bone, bursa, DDFT) when investigating chronic forelimb lameness, as newer imaging reveals additional pathologic involvement
Key Findings
- •Navicular syndrome is a chronic progressive disease affecting the navicular bone, bursa, DDFT, and associated soft tissue structures of the navicular apparatus
- •Radiographic changes of the navicular bone are not pathognomonic for navicular syndrome, and not all clinically affected horses show radiographic changes
- •CT and MRI imaging can identify lesions not observed on radiographs, playing an important diagnostic role in navicular syndrome
- •Anatomic structures beyond the navicular bursa, bone, and DDFT may play important roles in navicular syndrome pathophysiology