The minimally important change debate: why one size does not fit all – lessons from orthopaedics

Is the minimally important change (MIC) still a reliable metric? With the scientific community currently debating the limitations of single-value thresholds in patient-reported outcomes, our latest research in the Journal of Patient-Reported Outcomes offers a timely perspective. We explore the Oxford Hip and Knee scores to provide new recommendations for more accurate outcome measurement. In this blog, we share our findings and discuss what this shifting landscape means for patients and providers alike.

What is the minimally important change?

The MIC is a cornerstone concept in the field of patient-reported outcome measures (PROMs), serving as the bridge between statistical data and clinical relevance. In essence, it is the smallest improvement (or decline) that a patient actually feels is significant to their daily life [1]. However, there are still uncertainties about how we calculate and apply this threshold. The scientific community is currently in the midst of a debate about whether these “single values” are actually helping us, or if they are leading us astray.

A closely related concept is the minimally important difference (MID); while MIC typically refers to an individual’s improvement over time, MID often describes the smallest difference between groups of patients that is considered significant. The MIC is the focus of this blog. More details on the MID are available in Terwee et al. (2021) [1].

Our contribution to the field

Our paper, “Revisiting minimally important changes for the Oxford Hip and Knee scores” was recently published in the Journal of Patient-Reported Outcomes [2]. Using a dataset of over 380,000 records from the NHS, we took a hard look at the Oxford Hip Score (OHS) and Oxford Knee Score (OKS).

The OHS and OKS are condition-specific PROMs designed to let patients report on their own health. Each consists of 12 questions that cover the reality of living with a hip or knee condition, measuring everything from pain levels to how much the condition interferes with daily activities like self-care and walking. Because previous research suggested that a patient’s starting point might influence what they consider a “meaningful” improvement, we wanted to take a deeper look at how these scores behave in the real world.

Our study analysed data from a large cohort of patients undergoing elective hip or knee replacements between 2015 and 2022. Patients completed the OHS or OKS, alongside a general health measure (the EQ-5D-5L), both before surgery and six months after. To understand what the scores meant to the patients, we used a five-point Global Transition Item (GTI). This asked patients to rate their improvement from “much better” to “much worse.” We then mapped the change in OHS and OKS against these patient ratings, and categorised patients by their baseline health status to see if those who started with worse symptoms perceived “improvement” differently than those who started with milder symptoms.

Our findings arrive at a critical moment. We confirmed that traditional, one-size-fits-all MIC values are potentially unreliable as they may vary significantly depending on patient baseline scores. For example, we observed that the MIC for patients with the worst knee or hip symptoms before surgery was considerably larger than for those patients with fewer symptoms. This means that a meaningful change required greater levels of improvement on the PROM scores for patients with the severest symptoms. Our research quantifies this discrepancy, demonstrating that “importance” is a moving target.

Instead of a single metric, we argue for a more robust approach that combines baseline data, post-intervention scores, and change scores to truly understand a patient’s journey.

The wider debate

Our paper adds to the call for the status quo of the MIC to be questioned, with a number of recent commentaries arguing that the MIC should be challenged. Earlier this year, Whitehurst et al. (2026) published a provocative “denunciation” of applying MIDs to health state values (utilities) [3]. They argue that for preference-weighted scales, any improvement is important, and attempting to impose a “minimal” threshold on it lacks context and can be misleading.

This commentary was part of a back-and-forth with Johnson and Al Sayah (2026), who contend that there is “nothing mystical” about these differences [4]. They suggest that while the maths is complex, these thresholds remain vital tools for interpreting health measurement scales, provided we use them correctly.

Adding even more weight to this shift is Vickers et al. (2025), who have called for researchers to “drop the M” [5]. They argue that “Minimal” importance and change are not independent properties of an instrument. In their view, determining importance as a single statistical value is fundamentally flawed.

Why this matters for patients and providers

The common thread through all these papers, including our own, is a move toward sophistication over simplicity.

While it is tempting to use a single 9-point or 5-point rule to judge a surgical success, our research shows that the reality is more nuanced. By moving away from rigid, single-value thresholds and toward a more contextualised understanding of patient outcomes, we can make better decisions in clinical trials, healthcare service evaluations and, most importantly, individual patient care.

As the debate continues to unfold, our team remains committed to ensuring that the “patient voice” captured in these scores is interpreted with the highest possible accuracy.

Want to find out more?

To delve deeper into our study on minimally important changes for the Oxford Hip and Knee scores, read our full paper. If you’re interested in finding out more about our work in patient-reported outcome measures, please contact us.