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Open Access

Minimal important change or difference for the oxford hip and knee scores following joint replacement surgery

  • Kristina Harris1,
  • Andrew Price1,
  • Jill Dawson1,
  • Helen Doll1,
  • David Murray1,
  • Andrew Carr1 and
  • David Beard1
Trials201314(Suppl 1):O51

Published: 29 November 2013


Detectable ChangeMeaningful DifferenceKnee ReplacementSecondary DataJoint Replacement


i) to present a range of estimates of meaningful or minimal important changes/differences for the Oxford Hip Score (OHS) and the Oxford Knee Score (OKS) based on different approaches, and (ii) to identify the estimates that are most consistent and useful for application in specific contexts.

Study design and setting

Secondary data analysis of the NHS PROMS dataset which included 137,109 patients listed for hip replacement surgery and 156,788 patients listed for knee replacement surgery.


Anchor based Minimal Important Difference (MID) was ~ 5 points for the OKS and the OHS and Minimal Important Change (MIC) was ~ 9 points for the OKS and ~ 11 points for the OHS. Distribution based methods showed that the Minimal Detectable Change (MDC90) for the OKS and OHS respectively were 4 and 5 points.


This study produced a range of context-specific estimates of minimal important change/difference for the OKS/OHS. We would recommend, based on current evidence, that the OKS/OHS MIDs are used to indicate meaningful difference between patients (e.g. in clinical trials) and the OKS/OHS MICs to indicate meaningful change from baseline in a single group design. The MDC90 should be used to indicate change beyond measurement error on individual patients.

Authors’ Affiliations

University of Oxford, Oxford, UK


© Harris et al; licensee BioMed Central Ltd. 2013

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


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