Reliability of measuring hip abductor strength following total knee arthroplasty using a hand-held dynamometer

Purpose: To investigate the test-retest reliability of measuring hip abductor strength in patients with total knee arthroplasty (TKA) using a hand-held dynamometer (HHD) with two different types of resistance: belt and manual resistance. Method: Test-retest reliability of 30 subjects (17 female, 13 male, 71.97.4 years old), 9.22.7 days post TKA was measured using belt and therapist resistance. Retest reliability was calculated with intra-class coefficients (ICC3,1) and 95% confidence intervals (CI) for both the group average and the individual scores. A paired t-test assessed whether a difference existed between the belt and therapist methods of resistance. Results: ICCs were 0.82 and 0.80 for the belt and therapist resisted methods, respectively. Hip abductor strength increases of 8N (14%) for belt resisted and 14N (17%) for therapist resisted measurements of the group average exceeded the 95% CI and may represent real change. For individuals, hip abductor strength increases of 33N (72%) (belt resisted) and 57N (79%) (therapist resisted) could be interpreted as real change. Conclusions: Hip abductor strength can be reliably measured using HHD in the clinical setting with the described protocol. Belt resistance demonstrated slightly higher test-retest reliability.