A comparative study of proximal hindlimb flexion in horses: 5 versus 60 seconds.
Authors: Armentrout A R, Beard W L, White B J, Lillich J D
Journal: Equine veterinary journal
Summary
# Editorial Summary The flexion test remains a cornerstone of equine lameness evaluation, yet standardised protocols for test duration have never been established in peer-reviewed literature. Armentrout and colleagues addressed this gap by having 15 experienced equine clinicians blindly assess lameness videos of 34 horses before and after proximal hindlimb flexion, comparing responses to 5-second versus 60-second flexion durations in random order. Significantly, 60-second flexions elicited positive responses 26% more frequently than 5-second flexions (P<0.0001), with clinicians providing identical interpretations only 74% of the time—a finding that challenges assumptions about flexion test interchangeability. Intra-assessor reliability was moderate (κ = 0.49, 75% agreement), and notably, whichever flexion was performed first was more likely to be scored positive, suggesting fatigue effects or anchoring bias in clinical interpretation. For practitioners, this research suggests that test duration meaningfully influences results; standardising flexion duration in your clinical protocol and always documenting which limb was flexed first will improve consistency, though clinicians with demonstrated good agreement between 5 and 60-second flexions may be able to use shorter durations without compromising diagnostic validity.
Read the full abstract on PubMed
Practical Takeaways
- •Duration of flexion testing matters: 5-second and 60-second tests produce different results, so standardise your protocol and be consistent within your practice
- •If using shorter 5-second flexion tests, recognise they are less sensitive than 60-second flexion and may miss some positive responses
- •Test order affects interpretation—perform flexion tests in a consistent sequence and be aware that fatigue may influence subsequent limbs being tested
Key Findings
- •Proximal hindlimb flexion for 60 seconds was significantly more likely to be called positive than 5-second flexion (P<0.0001)
- •Interpretation agreement between 5 and 60-second flexion was only 74%, indicating they do not yield equivalent results
- •First flexion test performed was more likely to be called positive than subsequent flexions (P=0.029), suggesting fatigue or habituation effects
- •Intra-assessor agreement averaged 75% (κ=0.49), indicating moderate but not high repeatability among experienced clinicians