Abstract
Background Because people with total knee arthroplasty (TKA) have persistent functional limitations and disability, identifying modifiable risk factors for persistent disability is warranted. Before surgery, people have pervasive lower extremity muscle weakness. The fact that hip abductor muscle strength is often not targeted in postoperative rehabilitation may contribute to functional limitations.
Objective Study objectives were: (1) to examine the reliability of handheld dynamometry (HHD) for measuring hip abductor strength and (2) to determine whether hip abductor strength contributes to physical function beyond the contribution of quadriceps muscle strength.
Design This was a cross-sectional study.
Methods Two-hundred ten participants underwent quadriceps and hip abductor muscle strength testing and measurement of physical function (performance-based and self-reported outcomes). Correlation and regression equations were built to determine the relationships of strength, pain, and functional ability. A subset of 16 participants underwent hip abductor strength testing at 2 sessions to determine the reliability of the measure.
Results Measuring hip abductor strength with HHD yielded excellent relative reliability, with an intraclass correlation coefficient (ICC [2,3]) of .95 and a 95% confidence interval of .86 to .98, but moderate absolute reliability, with a minimal detectable change (with 95% confidence) of 47.6 N and a 95% confidence interval of 35.5 to 76.5. Hip abductor strength made a significant additional contribution to performance-based measures of physical function after anthropometric covariates and quadriceps muscle strength were accounted for. Hip abductor strength did not show bivariate correlations with patient-reported measures of physical function and did not contribute to patient-reported physical function after covariates and quadriceps muscle strength were accounted for.
Limitations A cause-and-effect relationship between hip abductor strength and physical function could not be established.
Conclusions In people with unilateral TKA, HHD testing of hip abductor strength is reliable. Hip abductor strength contributes to performance-based but not patient-reported measures of physical function in people with unilateral TKA.
Footnotes
Dr Alnahdi and Dr Snyder-Mackler provided concept/idea/research design. All authors provided writing and data analysis. Dr Alnahdi provided data collection. Dr Zeni and Dr Snyder-Mackler provided facilities/equipment. Dr Snyder-Mackler provided project management, fund procurement, institutional liaisons, and consultation (including review of manuscript before submission).
This study was approved by the Human Subjects Review Board at the University of Delaware.
This study was supported by National Institutes of Health grants P20RR016458 and K12HD055931. The authors extend their appreciation to the College of Applied Medical Sciences Research Center and the Deanship of Scientific Research at King Saud University for funding Dr Alnahdi's participation in this research.
- Received July 26, 2013.
- Accepted March 14, 2014.
- © 2014 American Physical Therapy Association
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