In vitro evaluation of metacarpophalangeal joint loading during simulated walk.
Authors: Den Hartog S M, Back W, Brommer H, van Weeren P R
Journal: Equine veterinary journal
Summary
# Editorial Summary: Metacarpophalangeal Joint Loading During Walk Understanding how forces distribute across the fetlock joint during locomotion is crucial for comprehending why certain horses develop joint disease and fractures. Den Hartog and colleagues used cadaveric limbs from eight mature Warmbloods, positioning them in a pneumatic loading device at six points throughout the walk stride whilst measuring pressure across the proximal phalanx articular surface using pressure-sensitive films at seven distinct sites. Loading pressures increased significantly after mid-stance (positions 4–6) compared to earlier phases (positions 1–3), reflecting the biphasic loading pattern typical of walk at most measurement sites; however, the central sagittal groove demonstrated a linear pressure increase throughout stance rather than this biphasic pattern. Medial compartment pressures were significantly higher than lateral pressures across all measurement points—a distribution that aligns precisely with where cartilage degeneration initiates in naturally occurring fetlock osteoarthritis, suggesting biomechanical predisposition to this pathology. These findings have clear implications for farriers and veterinarians: the pronounced medial loading bias warrants attention to trim balance and medio-lateral symmetry, whilst the disproportionate loading of the central groove relative to peripheral joint surfaces may explain the stress fracture patterns observed in proximal phalanx and distal metacarpal bones, potentially informing management strategies for high-risk individuals.
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Practical Takeaways
- •Understanding that medial loading predominates during walk helps explain why osteoarthritis of the MCP joint characteristically starts medially—consider this when evaluating early degenerative changes or shoeing to manage joint loading.
- •The discrepancy between central groove and lateral loading creates high stress differences that may predispose to stress fractures in the proximal phalanx and distal metacarpal; this supports biomechanical management strategies aimed at load distribution.
- •The biphasic loading pattern typical across most joint sites suggests that joint support interventions should account for the significant load spike after mid-stance when designing therapeutic or preventive shoeing approaches.
Key Findings
- •Pressures in the MCP joint after mid-stance (positions A4-A6) were significantly higher than before mid-stance (positions A1-A3), demonstrating biphasic loading pattern during walk at most measurement sites.
- •Medial articular surface loading was significantly higher than lateral loading (P < 0.05), with higher pressures recorded at medial sites (S4, S5, S6) compared to lateral sites (S1, S2, S3).
- •The sagittal groove (S7) showed linear pressure increase throughout stance phase rather than biphasic pattern, creating large stress differences at end of stance phase.
- •Heavy medial loading pattern coincides with the anatomical location where osteoarthritic cartilage degeneration typically initiates in equine MCP joints.