Injury to the palmar supporting structures of the fetlock alters limb stiffness and fetlock angle.
Authors: Hanousek Katherine, Fiske-Jackson Andrew, O'Leary Lauren, Smith Roger K W
Journal: Equine veterinary journal
Summary
# Editorial Summary Hanousek and colleagues employed in vivo gait analysis using floor-mounted scales and electrogoniometry to non-invasively assess fetlock mechanics in horses with and without palmar supporting structure injuries. Measuring limb stiffness (calculated from the relationship between fetlock angle and load) and static fetlock conformation across 42 uninjured forelimbs, 19 uninjured hindlimbs, 18 forelimbs with superficial digital flexor tendon (SDFT) injury, and 5 hindlimbs with suspensory ligament (SL) injury revealed distinct patterns of tissue-specific adaptation. Forelimbs demonstrated significantly greater normalised stiffness than hindlimbs (22.3 versus 16.4 × 10⁻³ degree⁻¹), yet chronic SDFT injuries showed no detectable change in stiffness or conformation; by contrast, SL-injured hindlimbs exhibited both increased stiffness and increased fetlock angle, indicating structural lengthening of the ligament following injury. These findings suggest fundamentally different load-sharing responses between tendons and ligaments, with SL injuries producing measurable biomechanical changes that might be detectable through relatively simple clinical assessment tools—valuable information for monitoring recovery and rehabilitation, though the small SL injury cohort and lack of lameness correlation limit broader interpretation at present.
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Practical Takeaways
- •Non-invasive measurement of fetlock angle and limb stiffness using floor scales and electrogoniometer can detect structural changes following suspensory ligament injury, potentially useful for monitoring rehabilitation and return to work decisions
- •Hindlimb suspensory ligament injuries show persistent biomechanical changes (increased stiffness and fetlock angle), whereas forelimb SDFT injuries do not produce long-term measurable changes in limb mechanics—suggesting different healing trajectories or functional compensation between fore and hind limbs
- •Understanding baseline differences in stiffness between forelimbs and hindlimbs is important for interpreting post-injury measurements and detecting pathology-specific gait changes
Key Findings
- •Forelimb stiffness (22.3 × 10⁻³ degree⁻¹) is significantly higher than hindlimb stiffness (16.4 × 10⁻³ degree⁻¹) when normalized to body weight (p<0.001)
- •Forelimb SDFT injury does not alter limb stiffness or fetlock conformation in the long-term
- •Hindlimb SL injury significantly increases both limb stiffness and fetlock angle (p=0.009 and p=0.002 respectively), suggesting increased SL length post-injury
- •Limb stiffness correlates with horse weight in both forelimbs (p<0.001) and hindlimbs (p=0.006)