Effect of a unilateral hind limb orthotic lift on upper body movement symmetry in the trotting horse.
Authors: Vertz, Deblanc, Rhodin, Pfau
Journal: PloS one
Summary
# Editorial Summary: Orthotic Lifts and Movement Adaptation in Trotting Horses Limb length asymmetries are known to alter weight-bearing and propulsive forces in horses, yet the immediate postural compensations remain poorly characterised. Vertz and colleagues used inertial sensors to measure vertical displacement of the poll, withers, sacrum and hip points in eleven horses trotting under five conditions: baseline and with 15mm or 30mm orthotic lifts applied unilaterally to either hind limb. The most significant finding was pronounced pelvic asymmetry—the pelvis dropped further during stance on the shortened limb and elevated more during and after stance on the lengthened limb, with asymmetry changes ranging from 3–7mm for 15mm lifts and 4–10mm for 30mm lifts (P<0.001), whereas compensatory head and withers movements were inconsistent and hip hike remained unaffected. These results suggest horses immediately redistribute weight-bearing towards the shorter limb whilst increasing pushoff from the longer one, a pattern with clear implications for managing chronically lame horses or those with significant hoof asymmetries between paired limbs. The findings are limited by small sample size (n=11), absence of direct force plate data, and assessment of only acute responses without follow-up measurements; nonetheless, the pelvic-level compensation observed supports using targeted orthotic management as part of lameness rehabilitation protocols.
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Practical Takeaways
- •Artificial limb length changes via orthotic lifts produce measurable, consistent pelvic biomechanical adaptations within single trotting sessions—consider this when correcting hoof imbalances or chronic lameness with uneven foot wear
- •The lack of consistent head/withers compensation despite clear pelvic changes suggests horses may prioritize pelvic stability over upper body symmetry when managing limb length differences
- •Orthotic interventions for horses with chronic lameness or contralateral hoof shape asymmetry should account for immediate pelvic movement redistribution as a positive weight-management strategy
Key Findings
- •Orthotic lifts of 15-30mm induced pelvic movement asymmetry changes of 3-7mm (4-10mm respectively), with increased downward pelvic movement during stance of the shorter limb
- •Pelvic asymmetry changes were statistically significant (P<0.001) and consistent across all lift conditions, but head and withers compensatory movement showed inconsistent asymmetry patterns
- •Hip hike (tuber coxae movement asymmetry) was unaffected by orthotic lift application (P=0.348), suggesting selective pelvic adaptation without compensatory hip movement
- •Results indicate immediate weight-bearing preference shifts toward the shorter limb with increased pushoff from the longer limb, mimicking force distribution patterns reported in humans