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Br J Sports Med. 2019 May 9. pii: bjsports-2018-100260. doi: 10.1136/bjsports-2018-100260. [Epub ahead of print]

It is good to feel better, but better to feel good: whether a patient finds treatment 'successful' or not depends on the questions researchers ask.

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Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense M, Denmark
Department of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense M, Denmark.
Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada.
Orthopaedics, Department of Clinical Sciences Lund, Faculty of Medicine, Lunds Universitet, Lund, Sweden.
Department of Orthopaedic Surgery, Copenhagen University Hospital Hvidovre, Hvidovre, Denmark.



In sports physiotherapy, medicine and orthopaedic randomised controlled trials (RCT), the investigators (and readers) focus on the difference between groups in change scores from baseline to follow-up. Mean score changes are difficult to interpret ('is an improvement of 20 units good?'), and follow-up scores may be more meaningful. We investigated how applying three different responder criteria to change and follow-up scores would affect the 'outcome' of RCTs. Responder criteria refers to participants' perceptions of how the intervention affected them.


We applied three different criteria-minimal important change (MIC), patient acceptable symptom state (PASS) and treatment failure (TF)-to the aggregate Knee injury and Osteoarthritis Outcome Score (KOOS4) and the five KOOS subscales, the primary and secondary outcomes of the KANON trial (ISRCTN84752559). This trial included young active adults with an acute ACL injury and compared two treatment strategies: exercise therapy plus early reconstructive surgery, and exercise therapy plus delayed reconstructive surgery, if needed.


MIC: At 2 years, more than 90% in the two treatment arms reported themselves to be minimally but importantly improved for the primary outcome KOOS4. PASS: About 50% of participants in both treatment arms reported their KOOS4 follow-up scores to be satisfactory. TF: Almost 10% of participants in both treatment arms found their outcomes so unsatisfactory that they thought their treatment had failed. There were no statistically significant or meaningful differences between treatment arms using these criteria.


We applied change criteria as well as cross-sectional follow-up criteria to interpret trial outcomes with more clinical focus. We suggest researchers apply MIC, PASS and TF thresholds to enhance interpretation of KOOS and other patient-reported scores. The findings from this study can improve shared decision-making processes for people with an acute ACL injury.


knee ACL; knee surgery; measurement; randomised controlled trial; rehabilitation

Conflict of interest statement

Competing interests: None declared.

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