Concurrent Validity and Reliability of Two-dimensional Frontal Plane Knee Measurements during Multi-directional Cutting Maneuvers.
Dimas Sondang Irawan, Chantheng Huoth, Komsak Sinsurin and 3 others
PMID 35136683WHAT IT FOUND
A cheap phone-camera test for knee collapse during sharp turns matched gold-standard motion capture well for 90-degree cuts, but not for 30-degree cuts.
It was highly reliable when repeated. Use it to screen athletes for high-angle cutting risk, not shallow turns.
Key findings
01The 2D camera measurement showed strong correlation with 3D motion capture for 90-degree cuts and moderate correlation for 60-degree cuts at peak force, but poor correlation for 30-degree cuts.
02The 2D measurement was highly consistent when the same therapist repeated it and when a second therapist measured the same video.
03The authors suggest this method is suitable for clinical screening of knee valgus during 60-degree and 90-degree cutting tasks.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study included only seven male participants, all soccer players with right-leg dominance, which severely limits generalizability to female athletes or other sports. The sample size is too small to establish robust normative data or detect subtle measurement errors. The authors note that pelvic rotation may interfere with 2D accuracy during shallow cuts, which was not fully controlled for.
Declared interests
The authors declared no conflicts of interest.
The easy way to misread this
Do not use this 2D video method to assess knee valgus during low-angle cuts (30 degrees) or assume it works for female athletes, as the study only validated it for sharp turns in a tiny group of male soccer players.