Reliability and validity of two-dimensional motion capture to assess ankle dorsiflexion motion and heel raise work.
Megan Dao, Hadley Mosby, Emma Westphalen and 7 others
PMID 37300968WHAT IT FOUND
Two-dimensional video analysis reliably measures ankle dorsiflexion and heel raise work in patients with Achilles tendinopathy.
While 2D methods consistently overestimate values compared to 3D motion capture, the error is small and predictable. This supports using remote video assessments for clinical monitoring.
Key findings
01Inter-rater reliability for 2D motion analysis tasks was good to excellent.
022D measurements systematically overestimated 3D ankle motion by 1.0 to 1.7 degrees during calf stretches.
032D measurements overestimated positive heel raise work by 76.8 Joules compared to 3D analysis.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study was conducted in a controlled laboratory setting, so results may not generalize to home-based telehealth assessments where lighting, camera angle, and participant positioning are less standardized. The sample size was small (18 participants), which may limit the precision of the reliability estimates. The 2D method consistently overestimated values, meaning the two systems are not interchangeable for absolute comparisons. The analysis focused on slow, sagittal plane movements; accuracy may decrease with faster or frontal plane motions.
Declared interests
No specific conflicts of interest or funding sources were declared in the provided text.
The easy way to misread this
Do not treat 2D video measurements as equivalent to 3D motion capture data. The 2D method systematically overestimates ankle dorsiflexion and heel raise work, so direct comparisons to 3D norms or previous 3D baselines will be inaccurate.