Quantification and age-related distribution of articular cartilage degeneration in the equine fetlock joint.
Authors: Brommer H, van Weeren P R, Brama P A J, Barneveld A
Journal: Equine veterinary journal
Summary
# Quantification and age-related distribution of articular cartilage degeneration in the equine fetlock joint The metacarpophalangeal (fetlock) joint sustains more traumatic and degenerative lesions than any other joint in the equine limb, yet the precise distribution of cartilage loss across the articular surface and its relationship to age remained poorly characterised. Brommer and colleagues examined the proximal articular cartilage of the first phalanx (P1) in 73 slaughter horses aged 0.4 to 23 years using both semiquantitative macroscopic scoring and quantitative cartilage degeneration indexing (CDI), measuring overall joint involvement and three specific anatomical regions of interest. Cartilage loss was markedly non-uniform: the medial dorsal surface showed the greatest degeneration (ranging from 10.6% at grade 0 to 63.1% at grade 5), whereas the lateral central fovea showed minimal involvement (1.5% to 15.2% across the same grades), with a consistent medial-to-lateral and dorsal-to-central gradient of disease severity. A moderate but significant positive correlation existed between overall CDI and age (r = 0.41), confirming that whilst age-related changes are inevitable, the specific patterns of cartilage degradation are driven primarily by biomechanical loading rather than chronological age alone. Understanding this heterogeneous distribution pattern is crucial for practitioners: it explains why early osteoarthritis may be easily missed on standard radiographs (which typically visualise dorsal surfaces poorly), supports the biomechanical basis for targeted therapeutic interventions, and provides a framework for predicting disease progression and developing location-specific diagnostic and treatment protocols.
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Practical Takeaways
- •Osteoarthritis in the fetlock develops progressively with predictable anatomical patterns; early detection using imaging should focus on medial dorsal cartilage surfaces where changes appear first
- •Age alone is not the primary driver of fetlock OA—biomechanical factors (loading patterns, conformation, training intensity) play a critical role, suggesting management interventions targeting movement and workload can slow progression
- •The heterogeneous distribution of cartilage damage across the joint surface supports tailored therapeutic approaches such as targeted joint injections or farriery modifications to redistribute loading pressure
Key Findings
- •High correlation (r=0.92) between semiquantitative macroscopic scoring and quantitative cartilage degeneration index (CDI) measurements in fetlock cartilage
- •Moderate but significant age-related increase in cartilage degeneration (r=0.41; P<0.001), with macroscopic Grade 0 showing CDI of 25±2.8% and Grade 5 showing 38.1±7.9%
- •Cartilage degeneration follows a specific distribution pattern: highest on medial dorsal surface (10.6-63.1% across grades), lower laterally and centrally, indicating biomechanical loading as a primary driver beyond age alone
- •Central foveal regions showed significantly lower degeneration than dorsal surfaces at all grades (P<0.05), suggesting focal loading concentration on dorsal articular surfaces