Interrater and Intrarater Reliability of Common Clinical Standing Balance Tests for People With Hip Osteoarthritis

BACKGROUND: Hip osteoarthritis (OA) is a common musculoskeletal condition affecting older individuals. Clinical balance tests are frequently used to assess standing balance in these people. There is insufficient information regarding the reliability of these tests. OBJECTIVE: The aim of this study was to estimate reliability and measurement error of 4 common clinical standing balance tests in people with hip OA. DESIGN: A prospective study was conducted with repeated measures between 2 independent raters within 1 session and within 1 rater over a 1-week interval. METHODS: Thirty people with hip OA were evaluated. Reliability was estimated for the Four-Square Step Test, Step Test, Functional Reach Test, and Timed Single-Leg Stance Test using intraclass correlation coefficients (ICC [2,1]). Measurement error was expressed as standard error of measurement and minimal detectable change. RESULTS: The Four-Square Step Test, Step Test, and Timed Single-Leg Stance Test were sufficiently reliable between raters (ICC=.85-.94, lower 1-sided 95% confidence interval [95% CI]=.71-.89), whereas the Step Test (standing on study limb) and Timed Single-Leg Stance Test (standing on nonstudy limb) were sufficiently reliable within a rater over a 1-week interval (ICC=.91, lower 1-sided 95% CI=.80-.83). The Step Test (standing on study limb) and Timed Single-Leg Stance Test (standing on nonstudy limb) achieved optimal levels of reliability (ICC >.90, lower 1-sided 95% CI >.70), with acceptable measurement error (<10%) for clinical outcome measures. The Functional Reach Test was not sufficiently reliable. A ceiling effect was detected for the Timed Single-Leg Stance Test. LIMITATIONS: Reliability was assessed only between 2 raters during a single session and within 1 rater over a 1-week interval, which limits generalizability. CONCLUSIONS: The Step Test (standing on study limb) is recommended as a highly reliable test with acceptable measurement error for assessing standing balance in people with hip OA.