Withers vertical movement symmetry is useful for locating the primary lame limb in naturally occurring lameness.
Authors: Persson-Sjodin, Hernlund, Pfau, Andersen, Forsström, Byström, Serra Bragança, Hardeman, Greve, Egenvall, Rhodin
Journal: Equine veterinary journal
Summary
# Editorial Summary Distinguishing primary forelimb lameness from compensatory head bobbing caused by hindlimb lameness remains clinically challenging, particularly when both present with asymmetrical head movement. This multicentre retrospective study analysed withers vertical displacement patterns in 317 lame horses across four European referral hospitals using three-dimensional motion capture, comparing movement asymmetry before and after diagnostic analgesia to identify which limb was actually primary. In forelimb lameness cases, head and withers asymmetry aligned in 80–81% of horses, both pointing to the same affected forelimb; conversely, hindlimb lameness produced discordant patterns in 69–72% of cases, with head asymmetry pointing ipsilaterally to the lame hindlimb whilst withers asymmetry indicated a contralateral forelimb. Notably, when compensatory head nods exceeded 15 mm in hindlimb lame horses (occurring in roughly 30% of cases), this conflicting head–withers pattern was present in 89–92% of those animals, providing a clear diagnostic signal. Clinicians performing quantitative lameness assessment can utilise withers movement metrics as a practical aid in localising the primary lame limb, particularly when compensatory strategies create ambiguity; however, individual variation in movement compensation patterns means motion capture findings should integrate with clinical examination findings rather than replace them entirely.
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Practical Takeaways
- •Use withers movement asymmetry alongside head nod patterns to differentiate primary forelimb from primary hindlimb lameness—if head and withers indicate different forelimbs, suspect hindlimb lameness
- •In horses with large compensatory head nods, withers motion capture can improve diagnostic accuracy by revealing the true location of primary lameness
- •Motion capture metrics provide objective quantification that can catch subtle compensatory patterns and improve diagnostic confidence during lameness investigations
Key Findings
- •In forelimb lame horses, 80-81% showed head and withers asymmetry indicating lameness in the same forelimb
- •In hindlimb lame horses, 69-72% showed head asymmetry ipsilateral to the lame limb but withers asymmetry diagonal to it, indicating different forelimbs
- •Large compensatory head nods (>15mm) occurred in 28-31% of hindlimb lame horses, with 89-92% showing head and withers asymmetry in different forelimbs
- •Withers asymmetry decreased linearly with reduced head or pelvic asymmetry in both forelimb and hindlimb lameness