The force and contact stress on the navicular bone during trot locomotion in sound horses and horses with navicular disease.
Authors: Wilson, McGuigan, Fouracre, MacMahon
Journal: Equine veterinary journal
Summary
# Editorial Summary: Force and Contact Stress on the Navicular Bone During Trot Understanding the biomechanical stresses acting on the navicular bone is crucial for identifying whether mechanical overload from conformation or farriery contributes to navicular disease development. Wilson and colleagues measured both force and contact stress (rather than force alone) on the navicular bone in six sound horses and eight with navicular disease during trotting, using a forceplate system combined with a novel technique to quantify the contact area between the deep digital flexor tendon and bone *in vivo*. Peak forces and stresses were broadly comparable between groups overall (5.62 versus 6.97 N/kg and 2.74 versus 3.07 MPa respectively), but diseased horses demonstrated approximately double the stress in early stance phase, reflecting significantly elevated deep digital flexor tendon loading—an apparent compensatory mechanism to offload the heels. These findings suggest that navicular disease may involve altered loading patterns and early-stance biomechanics rather than simply sustained excessive stress, which has important implications for therapeutic shoeing strategies targeting load redistribution and proprioceptive feedback during weight-bearing transitions.
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Practical Takeaways
- •Navicular disease horses show abnormal loading patterns early in stance phase, suggesting therapeutic interventions (shoeing, muscle conditioning) should target this period to reduce compensatory tension
- •The attempt to unload heels observed in diseased horses indicates pain-driven compensation; farriery that naturally supports heel loading early in stride may help normalize deep digital flexor recruitment patterns
- •Standard force measurements alone may mask pathological stress concentrations—assessment of contact area and pressure distribution provides more complete understanding of navicular pathomechanics
Key Findings
- •Peak force and stress were similar between normal (5.62 N/kg, 2.74 MPa) and diseased horses (6.97 N/kg, 3.07 MPa) at peak stance phase
- •Horses with navicular disease exhibited approximately double the force and stress in early stance phase compared to controls
- •Increased early-stance loading in diseased horses was attributed to deep digital flexor muscle contraction attempting to unload the heels
- •Contact area correction revealed stress differences not apparent from force measurements alone