The relationship between isokinetic strength and functional performance tests in patients with knee osteoarthritis.
Panagiotis Gkrilias, Elias Tsepis, Zinon Kokkalis and 2 others
PMID 29950786WHAT IT FOUND
In 40 knee osteoarthritis patients, worse 12-stair and 30-second chair stand scores were linked with lower thigh muscle strength.
If specialised strength testing is unavailable, poor performance on these tests may prompt quadriceps and hamstring strengthening, but this is an association, not proof.
Key findings
01At 120°/s, knee extension and flexion peak torque adjusted for body weight were significantly correlated with 6-minute walk, timed up and go, 30-second chair stand, and 12-stair test performance; at 180°/s the correlations were slightly lower.
02The 12-stair test and 30-second chair stand were significant predictors of all isokinetic strength variables, and the 6-minute walk test also predicted knee flexion at 120°/s.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
This was a cross-sectional association study, not a randomised trial, so it cannot show that strengthening based on test scores will improve function. The sample was 40 patients with radiographic grade 2 or 3 knee osteoarthritis, selected to be functional enough for testing, so findings may not apply to more severe or non-ambulatory patients. The authors used stepwise regression with a small sample, and they did not compare different treatment groups or follow patients over time. Strength testing used only 120°/s and 180°/s, because the authors avoided 60°/s due to possible knee overload and pain, so results may not reflect lower-speed strength. The Discussion's explanations for why the 12-stair and chair stand tests predicted strength are author interpretation, not tested in this study.
Declared interests
One author received a PhD scholarship from the General Secretariat for Research and Technology and the Hellenic Foundation for Research and Innovation. The remaining authors declared no conflicts, and all authors declared no competing interests.
The easy way to misread this
Do not conclude that poor stair or chair stand performance proves thigh muscle strength loss, or that prescribing strengthening based on these tests will improve function. The study measured association at a single time point in 40 patients and did not test an intervention.