Intra-rater reliability and criterion-related validity of using an accelerometer to measure the impact force and knee joint sway during single-leg drop landing.
Shogo Okamoto, Ryuta Saito, Masaaki Sakamoto
PMID 31037001WHAT IT FOUND
A shin-mounted sensor reliably tracked the timing of peak landing force, matching laboratory standards.
However, it poorly measured side-to-side knee sway compared to force plates. Use this tool to assess shock absorption timing, but do not rely on it to quantify knee instability.
Key findings
01The accelerometer showed high correlation with force plate data for the time to peak force and loading rate, indicating good validity for shock absorption metrics.
02The sensor's measurement of knee joint sway (mediolateral acceleration) did not significantly correlate with the force plate's center of pressure sway, showing poor criterion validity for this specific outcome.
03Intra-rater reliability for the sway measurement was moderate (ICC 0.62) with a wide confidence interval, unlike the high reliability found for force timing metrics.
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 ten healthy participants, all of whom were young college athletes, so results may not apply to patients with actual ACL injuries or older populations. The sample size was too small to robustly determine the reliability of the knee sway measurement, which showed a wide confidence interval. The sensor was attached to the shin, which is further from the body's center of mass than the trunk, potentially affecting accuracy for certain movements.
Declared interests
None declared.
The easy way to misread this
Do not assume the sensor accurately measures knee joint sway just because it accurately measures impact force timing. The study found no significant correlation between the sensor's sway data and the gold-standard force plate measurements for that specific variable.