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Objective: To compare the responsiveness of two unilateral lower-limb performance-based tests, the one-leg rise test and the maximal step-up test, with the bilateral 30-second chair-stand test and the self-reported measure of physical function (HOOS/KOOS). Specific aims were to evaluate responsiveness, floor/ceiling effect and association between the instruments.

Method: Data was included from 111 participants, mean age 61.3 years (8.3), with clinically verified hip or knee osteoarthritis, who reported less than 150 minutes/week of moderate or vigorous intensity physical activity. Responsiveness, how well the instruments captured improvements, was measured as Cohen's standardised mean difference for effect size, and was assessed from baseline to 12 months following a physical activity intervention. Other assessments were floor and ceiling effects, and correlations between tests.

Results: The maximal step-up test had an effect size of 0.57 (95% CI 0.37, 0.77), the 30-second chair-stand 0.48 (95% CI 0.29, 0.68) and the one-leg rise test 0.12 (95% CI 0.60, 0.31). The one-leg rise test had a floor effect as 72% of the participants scored zero at baseline and 63% at 12 months. The correlation between performance-based tests and questionnaires was considered to be minor (r = 0.188 to 0.226) (p = 0.018 to 0.048).

Conclusion: The unilateral maximal step-up test seems more responsive to change in physical function compared to the bilateral 30-second chair-stand test, although the tests did not differ statistically in effect size. The maximal step-up test provides specific information about each leg for the individual and allows for comparison between the legs.