Characterizing knee loading asymmetry in individuals following anterior cruciate ligament reconstruction using inertial sensors.
Susan M Sigward, Ming-Sheng M Chan, Paige E Lin
PMID 27395452WHAT IT FOUND
The surgical leg showed lower knee loading and slower shank rotation than the other leg about 3 months after ACL reconstruction.
Sensor-measured shank rotation related to knee loading asymmetry even when walking timing looked normal.
Key findings
01Stance and swing times were similar between limbs, but peak knee extensor moment and peak shank angular velocity were smaller in the surgical limb.
02The surgical-to-non-surgical ratios averaged 0.71 for knee extensor moment and 0.83 for shank angular velocity.
03The surgical-to-non-surgical ratio of shank angular velocity predicted the surgical-to-non-surgical ratio of knee extensor moment.
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 19 people, so the relationship needs confirmation in a larger group. The sample size calculation was done after the study, not before. It was done in a lab with motion capture and force platforms, not in a clinic, and the authors say diagnostic accuracy still needs testing. The motion capture system changed during the study, which could affect consistency. The non-surgical leg was used as the reference, but it may not have had normal mechanics. Ground reaction forces were not measured by the inertial sensors, and the shank angular velocity ratio did not explain all of the knee loading ratio. Participants were only 8 to 16 weeks after surgery, so results may not apply to other recovery times.
The easy way to misread this
Do not conclude that inertial sensors are a validated clinical test for knee loading deficits. The study showed a lab-based relationship in 19 people about 3 months after surgery, and the authors say diagnostic accuracy in a larger population is still needed.