Evidence of reliability and responsiveness for the hip outcome score

Purpose: The purpose of this study was to offer evidence of test-retest reliability and responsiveness of both the Hip Outcome Score (HOS) activities of daily living (ADL) and sports subscales. Methods: We included 126 subjects in this study. They had a mean age of 41 years (range, 13 to 80 years; SD, 16). All 126 subjects underwent hip arthroscopy with the following procedures performed: labral debridement or repair (or both) (91%), osteoplasty (60%), chondral debridement-microfracture (51%), or capsular tightening (37%) (or some combination thereof). Of the subjects, 108 were in a group whose condition changed and 18 were in a group whose condition remained stable. The time between the first and second completion of the HOS averaged 7 months for both the change group (range, 55 to 420 days; SD, 96) and the stable group (range, 85 to 399 days; SD, 99). Results: The intraclass correlation coefficient values were 0.98 and 0.92 for the ADL and sports subscales, respectively, with minimal detectable change values of +/- 3 points. Using 2-way repeated-measures analysis of variance, we found that the subscales were responsive to change in status (P < .0005), with effect sizes of 1.2 and 1.5 for the ADL and sports subscales, respectively. The area under the receiver operating characteristic curves for the ADL and sports subscales were 0.88 and 0.90, respectively. The minimal clinically important difference values were 9 points and 6 points for the ADL and sports subscales, respectively. Conclusions: This study supports the use of the HOS as a self-reported evaluative outcome instrument with evidence of reliability and responsiveness for individuals who undergo arthroscopic hip surgery. A score change beyond 3 points represents a change beyond measurement error for the ADL and sports subscales. An increase in the score above 9 points and 6 points represents a meaningful increase for the ADL and sports subscales, respectively. Level of Evidence: Level III, diagnostic study.