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OBJECTIVES: To create estimates for clinically meaningful changes and differences in pain and joint function for the Oxford Hip and Knee Scores (OHS/OKS) in primary and revision joint replacement. STUDY DESIGN AND SETTING: 694,487 primary and revision joint replacement procedures were analyzed from the NHS PROMs dataset between 2012-2020. Minimal important changes (MIC) and differences (MID) were calculated using distribution and anchor-based methods (including receiver-operating characteristic (ROC) curve and predictive-modelling techniques). RESULTS: For comparison of two or more groups (such as in a clinic trial), MID estimates were ∼5 points. For cohort studies investigating changes over time in a single group of patients, MICgroup estimates were 12.4 points (primary hip replacement), 8.6 points (revision hip replacement), 10.5 points (primary knee replacement) and 9.4 points (revision knee replacement). For studies investigating changes over time at the individual patient level, MICadjusted estimates were ∼8 points, ∼6 points, ∼7 points and ∼6 points respectively. CONCLUSION: This study has calculated contemporary estimates of clinically important changes and differences for the OHS/OKS for primary and revision hip and knee replacement. These estimates can be used to inform sample size calculations and to interpret changes in joint function over time and differences between groups.

Original publication




Journal article


J Clin Epidemiol

Publication Date





159 - 168


Patient-reported outcome measures, Re-operation, Revision, Total hip replacement, Total knee replacement