Why every camera-based measurement needs its own validation

Clinical range-of-motion observation with camera in physical therapy

MedMeters literature review prepared 31 October 2026. The year in the article heading refers to the original study publication, not an earlier MedMeters posting date.

53 studiesreviewed across movement tasks · findings from external research

Clinical question

How consistent and valid are markerless motion systems across movement tasks and joints?

Study design

This systematic review evaluated 53 studies covering walking, squatting, jumping, running and cutting, comparing measurement reliability and agreement with marker-based systems.

What the researchers found

Reliability was often favorable, but differences from marker-based motion capture varied widely—roughly 0.2° to 28.6° depending on the joint, task and motion plane.

Why this matters for MedMeters

This supports MedMeters’ protocol-first approach: validate one measure at a time, set camera-quality thresholds, record uncertainty and decline to score videos outside validated conditions.

What this does not prove

The review spans many systems and tasks; its error range must not be presented as the expected accuracy of MedMeters. A validation dossier should be specific to each intended use and population.

Original peer-reviewed publication

Reliability and validity of lower extremity and trunk kinematics measured with markerless motion capture during sports-related and functional tasks: A systematic review
Yoma et al. · Journal of Sports Sciences · 2025
DOI: 10.1080/02640414.2025.2518359

External scientific evidence summary. Not medical advice. MedMeters is a concept under development and has not been evaluated in these studies. Clinical claims, validation and regulatory status must be established separately.