Agreement Between Isokinetic Dynamometer and Hand-held Isometric Dynamometer as Measures to Detect Lower Limb Asymmetry in Muscle Torque After Anterior Cruciate Ligament Reconstruction.
Angelica Ivarsson, Anna Cronström
PMID 36518830WHAT IT FOUND
Hand-held and isokinetic dynamometers do not agree on limb symmetry after ACL reconstruction.
The hand-held device detected significantly more flexion asymmetry than the isokinetic machine, but results differed by movement. Do not swap the two tools mid-rehabilitation, as they measure different things and give different answers.
Key findings
01Agreement between hand-held and isokinetic dynamometers for detecting limb symmetry index was low, with poor to fair Cohen's Kappa coefficients for both extension and flexion.
02The hand-held dynamometer detected significantly more participants with abnormal knee flexion symmetry compared to the isokinetic dynamometer, but there was no significant difference for knee extension.
03The study concludes that these instruments should not be used interchangeably for assessing strength symmetry after ACL reconstruction.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
This was an exploratory analysis of baseline data from a larger cohort, so there was no prior power calculation. The devices measured different types of strength (isometric vs. isokinetic) and at different positions, which may explain the lack of agreement. Limb symmetry index assumes the uninjured leg is a perfect baseline, but the injury and subsequent deconditioning may have affected both legs. The study only tested isometric strength at 90 degrees of flexion, which may not reflect functional positions for all patients.
Declared interests
The authors report no conflicts of interest related to this manuscript.
The easy way to misread this
Do not assume the hand-held dynamometer is 'better' because it found more asymmetry. It detected more flexion issues because it measures static strength at a specific angle, while the isokinetic machine measures dynamic strength through a range. The difference reflects what each tool is designed to do, not necessarily which patient is more impaired.