Biochemical characterisation of navicular hyaline cartilage, navicular fibrocartilage and the deep digital flexor tendon in horses with navicular disease.
Authors: Viitanen, Bird, Smith, Tulamo, May
Journal: Research in veterinary science
Summary
# Navicular Disease: Biochemical Evidence of Systemic Cartilage and Tendon Degeneration Navicular disease remains a significant cause of forelimb lameness, yet its pathophysiology is incompletely understood. Viitanen and colleagues investigated whether the condition represents a degenerative process affecting not only the navicular bone's cartilage surfaces but also its fibrocartilage and the deep digital flexor tendon, examining tissue samples from 18 lame horses against 49 sound controls. They measured key degradation markers—cartilage oligomeric matrix protein (COMP), glycosaminoglycans, metalloproteinases MMP-2 and MMP-9, and water content—across multiple tissue types. Lame horses demonstrated elevated COMP and MMP-2 concentrations in hyaline cartilage, whilst MMP-9 was detected in tendons of 79% of affected horses at significantly higher levels than in sound animals, indicating active matrix breakdown throughout the navicular apparatus. These findings strengthen the argument that navicular disease involves coordinated degenerative changes across cartilage and tendon, suggesting that management strategies may need to address systemic matrix degradation rather than treating the navicular bone in isolation—relevant considerations for farriers planning loading modifications, veterinarians selecting therapeutic interventions, and physiotherapists designing rehabilitation protocols.
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Practical Takeaways
- •Navicular disease involves biochemical breakdown of multiple tissue types (cartilage and tendon), not just cartilage damage, which may require multi-modal treatment approaches
- •Elevated metalloproteinase activity (MMP-2 and MMP-9) indicates active matrix degradation in affected horses, potentially supporting the use of anti-inflammatory or anti-protease strategies in management
- •The disease process extends beyond the navicular bone to involve adjacent joint structures, suggesting early intervention and comprehensive joint management may help slow progression
Key Findings
- •COMP content in hyaline cartilage and tendon was significantly higher in lame horses compared to sound horses (p<0.05)
- •MMP-2 concentration in hyaline cartilage was elevated in lame horses, with MMP-2 amounts significantly higher in tendons compared to other tissue types
- •79% of lame horses with lesions had MMP-9 present in tendons at higher concentrations than sound horses (p<0.05)
- •Matrix compositional changes occur across navicular hyaline cartilage, fibrocartilage, and DDFT in navicular disease, suggesting a degenerative joint disease-like process