Variation in gait parameters used for objective lameness assessment in sound horses at the trot on the straight line and the lunge.
Authors: Hardeman A M, Serra Bragança F M, Swagemakers J H, van Weeren P R, Roepstorff L
Journal: Equine veterinary journal
Summary
# Editorial Summary Objective lameness assessment using 3D motion capture is increasingly used clinically, but clinicians need reliable reference values to distinguish genuine changes in gait from normal variation. Hardeman and colleagues investigated repeatability of symmetry parameters in twelve owner-sound horses by collecting kinematic data across twelve examination sessions over 42 days, measuring movement at the head, withers and pelvis during straight-line and lunge work on both hard and soft surfaces. The researchers found substantial between-measurement variation, particularly at the head (12–20 mm depending on parameter), with considerably less variation at the withers (3–4 mm) and pelvis (4–6 mm); importantly, variation decreased with additional repetitions on the same day and across successive measurement days, and was notably lower on hard compared to soft surfaces and on straight lines compared to circles. Intraclass correlation coefficients indicated good repeatability for withers and pelvis parameters (0.76–0.85) but only moderate repeatability for head measurements (0.68), reflecting the head's greater inherent mobility and susceptibility to environmental factors. These findings carry significant implications for practice: when using motion capture to monitor gait changes in lameness assessment or rehabilitation, clinicians should account for 10–20 mm of variation at the head and allow for stabilisation through repeated measurements before drawing conclusions about subtle gait changes. The superior repeatability of pelvis metrics suggests these may be more reliable indicators for objective assessment protocols, whilst the increased variation on soft surfaces and lunging work warrants standardised testing conditions when serial measurements are intended for clinical comparison.
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Practical Takeaways
- •When performing repeated lameness assessments, expect considerable natural variation in head motion measurements (up to 20mm for RUD); baseline measurements taken on the first examination day may not be reliable comparators
- •Standardize lameness assessment protocols by using hard surfaces and straight-line trotting when possible to minimize measurement variation, and perform multiple repetitions (≥5) within a session for more stable readings
- •Pelvis symmetry parameters are more repeatable than head parameters; consider these more reliable landmarks when establishing individual reference values for objective gait analysis in clinical practice
Key Findings
- •Between-measurement variation was substantial for head motion (MinDiff 13mm, MaxDiff 12mm, RUD 20mm, RDD 16mm) but smaller for withers and pelvis
- •Variation decreased with increasing repetitions and was greater on the first measurement day compared to subsequent days
- •Hard surfaces produced less between-measurement variation than soft surfaces, and straight-line trotting showed less variation than circle/lunge work
- •Between-horse variation was substantially larger than within-horse variation, with ICC values of 0.68 (head), 0.76 (withers), and 0.85 (pelvis)