Histopathology in horses with chronic palmar foot pain and age-matched controls. Part 1: Navicular bone and related structures.
Authors: Blunden, Dyson, Murray, Schramme
Journal: Equine veterinary journal
Summary
# Editorial Summary Chronic palmar foot pain remains a significant cause of lameness in horses, yet the underlying tissue pathology driving clinical signs has been inadequately characterised. Blunden and colleagues examined histological specimens from 32 horses with documented palmar digital nerve-responsive forelimb lameness and 19 age-matched sound controls, systematically sampling eight anatomical sites including the navicular bone, deep digital flexor tendon, distal sesamoidean impar ligament (DSIL), collateral sesamoidean ligaments, navicular bursa, and distal interphalangeal joint structures. Lame horses demonstrated significantly greater pathological changes in the flexor and proximal/distal borders of the navicular bone, the DSIL and its insertion point, and the navicular bursa—notably, medullary lesions were consistently located dorsal to flexor cortical defects—whilst collateral sesamoidean ligaments, dorsal navicular bone, and DIP joint cartilage showed no significant difference between groups. These findings suggest that palmar foot pain involves a spectrum of interconnected soft tissue and bone pathology rather than isolated navicular disease, with adaptive and degenerative changes occurring concurrently across the palmar apparatus. For practitioners, this underscores the importance of comprehensive imaging and clinical assessment beyond single-structure diagnosis, and supports targeted preventative strategies addressing the biomechanical environment of the entire navicular apparatus rather than treating navicular bone pathology in isolation.
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Practical Takeaways
- •Palmar foot pain involves multiple structures beyond the navicular bone alone—assess DSIL, navicular bursa, and DDFT as part of a functional unit in lame horses
- •Not all navicular bone changes correlate with lameness; focal medullary lesions dorsal to FFC lesions appear most clinically relevant
- •Adaptive changes occur in navicular apparatuses of all horses; identifying which lesions cause pain and dysfunction should guide targeted treatment rather than treating all structural changes identically
Key Findings
- •Significant histological differences between lame and control horses in navicular bone medulla, flexor aspect, proximal/distal borders, DSIL insertion, and navicular bursa (p<0.05)
- •Pathological abnormalities in lame horses involved not only navicular bone but also DSIL and navicular bursa as a complex
- •No significant differences found in collateral sesamoidean ligaments, dorsal navicular bone, distal phalanx articular cartilage, or DIP joint collateral ligament lesions between groups
- •Navicular bone medullary abnormalities were generally found only dorsal to lesions of the flexor fibrocartilage complex