Effects of a preoperative exercise intervention targeting the non-operated limb in patients scheduled for total knee arthroplasty: a pilot study.
Shomaru Ito, Shinya Otani, Yasushi Naito and 7 others
Activity pain and chair-stand performance improved beyond measurement error after eight weeks of preoperative exercise in 24 patients awaiting knee replacement.
Other gains in strength and range of motion were small enough to be within measurement error. Resting pain did not change.
Key findings
1Activity-related pain dropped from 6.3 to 3.8 points, and the 30-second chair-stand test improved from 11.5 to 15.1 repetitions. These were the only two outcomes whose changes exceeded the minimal detectable change for measurement error.
2Knee extension strength on the non-operated side went from 0.97 to 1.06 N·m/kg, and hip abduction strength from 0.68 to 0.79 N·m/kg. Both changes were statistically significant but fell within the minimal detectable change (0.23 and 0.29 N·m/kg respectively), meaning they may reflect measurement error rather than true improvement.
3Resting pain went from 0.9 to 1.5 points (95% CI: −0.3 to 0.6), and this change did not exceed the minimal detectable change.
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What it does not show
Single-arm design with no control group, so you cannot separate the effect of exercise from natural fluctuation or the passage of time on the waiting list. Twenty-four patients at one centre; the authors note the true effect size may be smaller than the 0.6 they assumed for sample size, which may have left the study underpowered. Therapeutic ultrasound was included as part of the warm-up, which could have contributed to the pain reduction and cannot be separated from the exercise effect. Post-intervention testing was done within one week of the last session but not at a fixed time point, and analgesic use was not controlled. Multiple outcomes were tested without correction for multiple comparisons, increasing the chance that some significant results are false positives. No postoperative outcomes were measured, so the study cannot say whether any preoperative gains were maintained after surgery.
Declared interests
No external funding. The authors declare no conflict of interest.
The easy way to misread this
Do not read the significant changes in knee range of motion, muscle strength, and walking speed as confirmed improvements. The authors themselves note these changes fall within the minimal detectable change for measurement error, meaning the test cannot distinguish a real gain from random variation. Only the activity pain and chair-stand changes clearly exceeded that threshold. Also, this is a single-arm pilot with no control group, so even the two real changes could partly reflect the passage of time or the ultrasound warm-up rather than the exercise itself.
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