Pressure pain mapping of equine distal joints: feasibility and reliability
Authors: Jana Gisler, L. Chiavaccini, Severin Blum, S. Montavon, C. Spadavecchia
Journal: Frontiers in Pain Research
Summary
# Pressure Pain Mapping in Equine Distal Joints: A New Tool for Assessing Osteoarthritic Pain Osteoarthritis causes chronic pain and lameness in horses, yet current diagnostic methods focus on movement analysis without directly measuring peripheral pain sensitisation—a gap this research addresses by testing whether pressure pain thresholds (PPT) could serve as an objective assessment tool for joint pain. Researchers used a hand-held digital algometer to measure pressure pain thresholds at six periarticular sites across the metacarpophalangeal, proximal interphalangeal and distal interphalangeal joints in 40 clinically healthy horses (20 Warmbloods and 20 Freihergers), then reassessed 20 of these animals at two-week intervals to evaluate reliability. The procedure proved highly feasible, successful in 95% of testing sessions, with median PPT of 9.4 N overall; notably, the palmar proximal interphalangeal and dorsal distal interphalangeal joints showed significantly lower thresholds (8.4 N and 9.0 N respectively) than the latero-palmar metacarpophalangeal joint (9.9 N), whilst no difference emerged between left and right limbs. Inter-rater reliability was strong to excellent (0.81–0.85), yet intra-rater reliability varied considerably (0.50–0.68), suggesting that whilst different examiners can obtain comparable readings, consistency within individual raters requires further refinement. Before pressure pain mapping can be recommended clinically, future work must compare healthy and osteoarthritic joints, evaluate hind limb and proximal joint sites, and establish whether this method can detect pain sensitisation that gait analysis alone might miss.
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Practical Takeaways
- •Pressure pain mapping could potentially become a complementary lameness assessment tool for evaluating peripheral sensitization in arthritic horses, but requires further validation on diseased joints before clinical implementation
- •If adopting this technique, consistent inter-rater standardization is achievable (different assessors get similar results), but individual operator technique needs refinement to improve within-rater consistency
- •Different joint sites show naturally different sensitivity thresholds in healthy horses—baseline normative data for your specific joints of interest should guide interpretation of clinical cases
Key Findings
- •Pressure pain mapping of distal thoracic limb joints was feasible in 95% of healthy horses (95% CI 88–100%)
- •Palmar PIP and dorsal DIP joints showed significantly lower pressure pain thresholds (8.4 and 9.0 N respectively) compared to latero-palmar MCP (9.9 N)
- •Inter-rater reliability was good to excellent (ICC 0.81–0.85) for MCP joints, while intra-rater reliability was highly variable (ICC 0.50–0.68, ranging from poor to good)
- •No significant differences in pressure pain thresholds were found between left and right limbs in healthy horses