Digital Knee Osteoarthritis Mindset Intervention: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Digital Knee Osteoarthritis Mindset Intervention (NCT05698368), a randomized na study. The primary outcome is Change From Baseline in Knee Pain Measured by Numeric Pain Rating Scale.

2. Clinical Question

The trial aimed to test whether an online mindset intervention changed mindsets and physical activity levels more than an education intervention in people with knee osteoarthritis. The posted primary endpoint focuses specifically on knee pain. It is therefore a narrower question than the trial’s broader stated aim: the primary measure does not itself describe physical activity or every aspect of mindset.

The result should be read as a set of group-level changes from baseline, not as a direct estimate of the difference between the mindset program and either comparator. The record gives separate means and 95% confidence intervals for the active comparator, mindset intervention, and survey-only groups. A comparative treatment effect for the primary endpoint is not reported in the registry record.

3. Trial Design

This is a randomized, double-masked, parallel-group study. The registry record lists an enrollment of 458 and identifies knee osteoarthritis as the condition studied. The trial is marked completed. Its recorded start date is 2023-04-10, and its primary completion date is 2023-09-19. No phase is applicable in the registry record.

Three groups appear in the posted primary results: an active comparator group, a mindset intervention group, and a survey-only group. The active comparator used educational videos and reflective questions intended to match the mindset intervention in duration and required attention. The video sources are described as YouTube videos about osteoarthritis. The survey-only group is described as completing the same surveys at the same time points without receiving additional content; its results label is “Survey-Only Group.” The group description also calls it a waitlist control.

The mindset intervention consisted of four modules, each containing videos and reflective questions. Participants were given one week to complete the program at their own pace. The module duration and total program duration are approximate, as stated in the registry record.

Random allocation and a parallel-group model describe how participants were assigned and followed across groups. “Double” masking is recorded, but who was masked and how masking was implemented are not reported in the registry record. The method used to generate the allocation sequence, allocation concealment, and any changes to the planned design are also not reported in the registry record. These omissions limit how specifically the conduct of randomization and masking can be assessed from the record alone.

The posted primary results include group sizes of 135 for the active comparator, 130 for the mindset intervention, and 143 for the survey-only group. These are the numbers attached to the primary endpoint results; the record does not explain whether they represent all randomized participants or an analysis subset.

4. Participant Flow and Accounting

The registry reports how participants moved through each stage of the study. All counts below are exactly as posted; missing counts are not inferred from other stages.

Overall Study

5. Baseline Characteristics

The table reproduces the baseline characteristics posted in the registry, which describe the participants analysed at baseline and help show whether the randomized groups were comparable.

6. Primary Endpoint

The registry lists the primary outcome as Change From Baseline in Knee Pain Measured by Numeric Pain Rating Scale, measured over Change from Baseline at 1 month.

The primary endpoint is change from baseline in knee pain at one month, measured using the Numeric Pain Rating Scale. The scale ranges from 0 to 10, where 0 means no pain and 10 means the worst pain. The posted result is expressed as a mean change in scale units for each group, with a 95% confidence interval.

A pain rating is a direct patient-reported measure of symptom intensity. Measuring change from baseline makes the endpoint about how scores shifted over the follow-up period, rather than only describing the score at one time point. A mean provides a group-level summary of those changes; it does not show how every participant’s pain changed, or how widely individual experiences varied.

The direction of the scale is important when reading the means: a negative change indicates a lower pain score at follow-up than at baseline, while a positive change indicates a higher score. The reported mean changes are -0.2 for the active comparator group, -0.5 for the mindset intervention group, and -0.1 for the survey-only group. These are separate within-group summaries. They do not by themselves establish how much the groups differed from one another.

The registry record does not report a minimally important difference or another threshold for judging the practical importance of a change on this scale. It also does not report a comparative estimate for the primary endpoint. As a result, the posted means can describe the direction and size of the observed group changes, but they do not settle whether a between-group difference is precise or meaningful.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The primary endpoint is a continuous measure: change in pain score, reported as a mean in scale units. For a continuous outcome, the mean summarizes the average observed change across the participants included in the analysis. It is a useful compact description, but it does not reveal the full distribution of individual scores or changes. The record does not report a standard deviation or another measure of participant-level spread for these group results.

What does a confidence interval describe?

A 95% confidence interval expresses uncertainty around an estimated mean under the assumptions of the method used to construct it. It is not a range containing 95% of individual participants’ changes. Nor does it make the estimate exact: different samples could produce different means and intervals. The registry record identifies the intervals as 95% confidence intervals but does not report the specific calculation method.

For the active comparator group, the mean change is -0.2 and the interval runs from -0.5 to 0.0. For the mindset intervention group, the mean is -0.5 and the interval runs from -0.8 to -0.1. For the survey-only group, the mean is -0.1 and the interval runs from -0.4 to 0.2. These are intervals for group means. They are not intervals for a difference between groups.

Why is a between-group estimate important?

In a randomized trial, the central comparative question is generally answered by estimating a contrast between randomized groups, such as a difference in mean change. That estimate directly describes how far apart the groups’ average outcomes are, while its confidence interval conveys uncertainty about the contrast. Separate group means can help describe the data, but they do not provide that contrast by themselves. The registry record does not report an estimable two-arm comparison for this continuous endpoint, so no direct comparative estimate can be interpreted.

It is also important not to treat a confidence interval’s relation to zero as a complete comparison. Whether a group’s mean change is distinguishable from no change is not the same question as whether two groups differ. A trial can have group means that each move in the same direction while the between-group contrast remains uncertain. The posted record does not give a formal comparative test or confidence interval for the primary endpoint.

What does the mean-change scale imply?

The endpoint is a change from baseline, not a follow-up score alone. Negative changes indicate lower scores than at baseline on a scale where higher scores indicate worse pain. The mean condenses those changes to one value per group. Without baseline scores or participant-level data, the record cannot show how baseline distributions compared, how variable the responses were, or whether a small number of observations influenced a group mean. Those details are not reported in the registry record.

In general, dispersion matters because participants in a clinical trial may respond differently. If observations vary substantially, a mean alone can conceal that heterogeneity. For some outcomes, data may also be more variable than a simple statistical model assumes; methods that account for such over-dispersion can be useful in those settings. This is a general statistical point, not a claim that over-dispersion occurred in this trial. The primary endpoint is continuous, and the posted summary does not include the information needed to assess its distribution or select a more specific model.

What should be understood about the planning illustrations?

The planning illustrations are hypothetical sample-size calculations based on a fraction of the observed effect, with a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. They are not the trial’s original design justification and should not be read as observed power. The registry record does not report the trial’s own sample-size justification, the effect size assumed when planning the trial, or the exact planning-illustration values in the registry record used for this interpretation.

In general, a planning calculation asks how many participants might be needed under specified assumptions to detect a chosen effect with a chosen operating characteristic. It depends on assumptions such as the target effect, variation, allocation, and analysis. A calculation based on an observed effect is especially illustrative: the observed estimate is uncertain, and the illustration does not establish what the completed trial could reliably detect. These calculations do not replace the reported estimate and uncertainty from the trial itself.

What can be said about the analysis?

The registry record marks the study randomized and parallel-group, and it reports the group-level endpoint summaries. It does not report the model used to analyze the primary endpoint, whether baseline values were included as a covariate, whether any adjustments were made, or how departures from model assumptions were handled. It also does not report a primary comparative estimate. The number of posted analyses is recorded as zero, while the group outcome summaries are present; the record does not explain this distinction. No statistical analysis plan or interim-analysis information is reported in the registry record.

These gaps matter because the methods determine which participants contribute to an estimate and how uncertainty is calculated. The reported 95% confidence intervals communicate precision for the group means, but they do not reveal every modeling choice. A complete interpretation therefore distinguishes the descriptive numbers that are posted from comparative or model-based claims that the record does not contain.

10. Multiplicity, Missing Data and Analysis Populations

The trial includes a primary pain endpoint and multiple secondary outcomes. The registry record lists measures addressing pain and functioning, osteoarthritis knowledge, perceived need for surgery, symptom-management strategy use, fear of movement, arthritis self-efficacy, physical and mental health, and body mindset. The record indicates that secondary results are posted, but the registry entries used for this summary do not include their estimates. The registry record does not report how many hypotheses were treated as confirmatory or whether an adjustment for multiple comparisons was planned or applied.

Multiplicity is a general statistical concern when many outcomes or comparisons are tested: the chance of at least one apparently notable result can increase as the number of tests increases. This does not establish that the trial’s findings are affected by multiplicity. The analysis plan and any multiplicity strategy are not reported in the registry record, so the handling of multiple outcomes cannot be assessed.

Missing-data methods are not reported in the registry record. The record does not specify how participants with incomplete follow-up were handled, whether imputation was used, or what assumptions were made about unobserved outcomes. The posted endpoint group sizes are available, but the record does not identify whether these are all randomized participants or only those with an available result. The analysis population—such as intention-to-treat or another defined population—is not reported in the registry record.

These omissions affect interpretation because missing outcomes and analysis-population choices can influence estimates and their uncertainty. The reported means and confidence intervals remain descriptive of the results as posted, but they cannot establish how sensitive the findings are to missing data or analysis choices. No interim analyses or stopping rules are reported in the registry record.

11. Safety Results

The registry reports serious adverse events as affected participants divided by participants at risk.

Deaths

Other (non-serious) adverse events

Participants with at least one non-serious event at or above the registry's 0% reporting threshold.

The registry record reports zero serious adverse events in each of the three groups: the active comparator group, the mindset intervention group, and the survey-only group. It also reports zero other adverse events in each group and zero deaths in each group. The numbers at risk are 135, 130, and 143, respectively, matching the group counts attached to the safety results.

These entries describe what was recorded in the registry. A reported zero means that no events of that category are listed for the relevant group in the posted results; it does not demonstrate that an event was impossible or that an intervention has no safety concerns. The record does not report details about how adverse events were collected, how long participants were monitored for safety, how events were defined, or how completeness of reporting was assessed.

No serious adverse-event terms are listed. The absence of listed terms should be read alongside the zero counts and the limitations of registry reporting, rather than as evidence about risks beyond the events captured in the record. These safety figures do not establish a comparative safety difference between groups.

12. What the Result Does, and Does Not, Mean

The posted primary results describe mean changes in knee pain from baseline at one month for three randomized groups. The mean change was -0.2 in the active comparator group, -0.5 in the mindset intervention group, and -0.1 in the survey-only group. Each estimate has a 95% confidence interval, which communicates uncertainty around the group mean. The negative direction corresponds to lower pain scores on the stated scale.

Those summaries do not provide a direct estimate of the difference between the mindset intervention and either comparator. The registry record does not report an estimable two-arm comparison for this continuous endpoint. It is therefore not possible to use the posted primary numbers alone to determine the size or precision of a comparative effect. Separate group means and intervals should not be treated as if they were a formal test of differences.

The result also does not show how each participant responded. A group mean can coexist with a range of individual experiences, and the record does not provide participant-level distributions or a measure of variation for the group changes. The confidence intervals concern uncertainty in the means, not the range of individual outcomes.

The endpoint addresses knee pain at one month. It does not by itself answer the broader stated question about mindset and physical activity, nor does it summarize every secondary measure. The record lists other outcomes, but their numerical results are not part of the registry entries for this interpretation. The registry record also does not report a threshold for clinical importance on the pain scale, so the practical importance of the posted changes cannot be judged from a stated benchmark.

Finally, a completed randomized study and posted group summaries are useful parts of the evidence record, but the available information does not establish the analysis population, missing-data approach, or primary comparative model. The conclusions that can be drawn should remain aligned with what is reported: descriptive group changes and their confidence intervals, without a reported comparative estimate for the primary endpoint.

13. Why This Trial Matters Statistically

This trial is statistically informative in part because it uses a randomized, parallel-group design and includes both an active educational comparator and a survey-only group. These groups represent different comparison contexts: one is intended to match the mindset program in duration and attention, while the other receives no additional content. The distinction matters when framing the question, because comparisons with these groups address different contrasts.

The primary endpoint is reported as a mean change with a 95% confidence interval for each group. This format makes both the estimate and its uncertainty visible. It also highlights an important reporting distinction: group-specific results are not the same as a direct between-group estimate. The registry record contains the former but does not report an estimable two-arm comparison for the continuous primary outcome.

The registry record also shows why outcome scope matters. The trial’s stated aim includes mindsets and physical activity, while the primary posted result concerns pain. The listed secondary outcomes cover several other aspects of knee osteoarthritis and health. A careful statistical reading keeps the primary endpoint separate from those broader constructs and does not infer results for measures whose numerical estimates are not reported in the record details.

Finally, the record includes safety counts and identifies the study as completed, while leaving several analysis details unreported. Distinguishing recorded observations from missing methodological information helps readers interpret the evidence without turning a descriptive result into a stronger comparative claim. The case illustrates the value of reporting not only group summaries, but also the contrast, analysis population, missing-data methods, and multiplicity strategy needed to understand them fully.

14. Limitations

• The posted summary statistics are the only data these results rest on; patient-level data, full protocols and statistical analysis plans are not available.
• Recalculated results are simple, unadjusted calculations from posted summaries. They do not replace the sponsor's prespecified analysis.

The main limitation for interpreting the primary result is the absence of a reported between-group estimate. The registry record provides a mean change and confidence interval for each group, but it does not report an estimable two-arm comparison for this continuous endpoint. As a result, the relative difference between the mindset program and either comparator cannot be quantified from the posted primary outcome details.

The record does not describe the primary analysis model or its assumptions, and it does not report whether baseline scores were included in the analysis. Baseline pain values and participant-level outcome distributions are not reported in the registry record. The record also does not identify the analysis population or explain whether the group sizes represent all randomized participants or participants with available outcome data.

Missing-data handling, multiplicity procedures, and the statistical analysis plan are not reported in the registry record. The time at which adverse events were assessed, event-collection procedures, and definitions are also not reported. Although the study is described as double-masked, who was masked and how that was done are not reported in the registry record.

Further limits include the lack of a reported clinical-importance threshold for the pain scale and the lack of secondary-outcome estimates in the registry record used for this account. Eligibility criteria, recruitment details, and the method of random sequence generation are not reported in the registry record. These gaps do not negate the posted results, but they constrain how fully the trial’s conduct, precision, and comparative findings can be assessed.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Digital Knee Osteoarthritis Mindset Intervention — NCT05698368.
• Registry record last updated 2025-02-13; status last verified 2025-02.
• Results first posted 2025-02-13.
• Data retrieved from ClinicalTrials.gov on 2026-11-09.
• Group sizes, means, event counts and sponsor-reported p-values are reproduced as posted. Effect estimates, confidence intervals and p-values not attributed to the sponsor are independently calculated from the posted summary statistics.

18. Record Summary

The registry record describes NCT05698368, “Digital Knee Osteoarthritis Mindset Intervention,” a completed randomized, double-masked, parallel-group study sponsored by Stanford University. It lists an enrollment of 458 and the condition knee osteoarthritis. The recorded study start date is 2023-04-10, with primary completion on 2023-09-19.

The groups were a digital mindset intervention, an active educational comparator, and a survey-only group. The primary endpoint was change from baseline in knee pain on the Numeric Pain Rating Scale at one month. Group means and 95% confidence intervals are posted for this endpoint, but an estimable two-arm comparison is not reported in the registry record.

The registry record also reports zero serious adverse events, zero other adverse events, and zero deaths in each group. Details about the primary analysis, missing data, analysis populations, and multiplicity are not reported in the registry record.