Comparison of Treatments Following Total Knee Replacement: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Comparison of Treatments Following Total Knee Replacement (NCT02237911), a randomized na study. The primary outcome is The Western Ontario and McMaster Universities Osteoarthritis Index Physical Function (WOMAC-PF)..

2. Clinical Question

3. Trial Design

The study is registered as a randomized, single-masked, parallel-group trial, with enrollment of 240 and status listed as completed. Its phase is recorded as not applicable. The sponsor is the University of Pittsburgh. The recorded start was 2014-12, and the primary completion date was 2017-09-07.

The treatment groups were a clinic-based outpatient exercise group, a community-based exercise group, and wait-listed usual medical care. The clinic program included supervised sessions followed by a home exercise program; the community program consisted of exercise classes. Both exercise descriptions specify twice-weekly participation during 3 months and sessions of about 60 minutes. The wait-listed comparator is described as receiving no intervention from the study. Further details of exercise delivery and the specific exercises are not reported in the registry record.

Single masking is recorded, but who was masked is not reported in the registry record. The record lists three outcome measures and 18 analyses, without enough detail to identify the analyses or connect each one to a particular outcome or time point. It identifies a secondary outcome, a composite score of performance-based tests of physical function. The primary outcome is patient-reported WOMAC-PF, measured at baseline, 3 months, and 6 months.

The record’s enrollment figure and its safety-group denominators are not interchangeable descriptions of the analysis population. For safety, the recorded at-risk denominators are 96 for each exercise group and 48 for usual medical care. Recruitment flow, allocation concealment, study setting, and the number of participants with primary-outcome data are not reported in the registry record.

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.

Before assignment: A total of 1372 subjects called for study information: 89 could not be contacted and 1283 were screened over the telephone. From those, 1032 were not eligible/willing to participate and 251 completed in-person screening. Eleven subjects failed in-person screening, resulting in 240 eligible subjects that were randomized into one of the study arms.

Overall Study

Reasons for not completing this period:

Analysis population for the primary outcome, as defined in the registry: Intention-to-treat approach was used among participants with follow-up data.

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 The Western Ontario and McMaster Universities Osteoarthritis Index Physical Function (WOMAC-PF)., measured over Baseline, 3 and 6 months.

The primary endpoint is the Western Ontario and McMaster Universities Osteoarthritis Index Physical Function measure, abbreviated WOMAC-PF. It is a patient-reported measure with 17 items. Each item uses a 5-point Likert-type scale scored from 0-4, with response descriptions ranging from none to extreme difficulty. The item scores are summed, with a maximum score of 68. Higher scores indicate worse physical function.

This endpoint is used to represent participants’ reported difficulty with physical tasks, rather than relying only on a clinician’s observation or a performance test. That perspective is relevant to a trial asking whether exercise approaches are associated with functional outcomes after total knee replacement. The record specifies the mean and standard deviation as the summary measures and lists assessments at baseline, 3 months, and 6 months.

Interpretation depends on the direction of the scale: a higher score represents worse function, not improvement. The registry record does not report group means, standard deviations, changes over time, between-group estimates, or confidence intervals for WOMAC-PF. It also does not report a threshold for an important change. Consequently, the endpoint’s definition is available, but the comparative magnitude and precision of the trial’s primary outcome are not.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

Means and standard deviations. WOMAC-PF is a continuous measure, and the registry specifies mean and standard deviation as its summary form. A mean describes the group’s average score; the standard deviation describes how spread out individual scores are around that average. General: these summaries help characterize score distributions, but they do not by themselves show whether groups differ. To assess a comparison, readers also need an estimated difference and its uncertainty, ideally with a confidence interval. Such comparative results are not reported in the registry record.

Scale direction and interpretation. The WOMAC-PF score increases with worse physical function. General: when interpreting a contrast in a measure whose higher values are worse, the sign and ordering of the contrast matter. A lower average score would correspond to less reported difficulty, while a higher average would correspond to more difficulty. The actual group averages and contrasts are not reported in the registry record, so this direction rule cannot be used to infer the trial’s result.

Repeated assessments. The primary outcome timeframe includes baseline, 3 months, and 6 months. General: repeated measurement can describe both initial group status and later scores, and it can help distinguish a follow-up score from change since baseline. A suitable analysis may need to account for the fact that observations from the same participant are related. The statistical model, treatment of baseline scores, and method for handling repeated observations are not reported in the registry record. It would therefore be inappropriate to attribute a particular modeling approach to this trial.

Randomization and masking. Randomized allocation is intended, in general, to make treatment groups comparable on average with respect to factors known and unknown at assignment. It does not guarantee identical groups, and the extent to which the intended comparison is preserved depends on conduct and analysis. The trial is recorded as randomized, single-masked, and parallel-group. The record does not identify who was masked or describe allocation concealment. Masking can reduce some forms of measurement or reporting bias, but its relevance depends on who knows the assigned group and which outcomes are assessed. Those details are not reported in the registry record.

Intention-to-treat wording. The primary outcome description says an intention-to-treat approach was used among participants with follow-up data. General: intention-to-treat analysis aims to retain participants in their assigned groups, which preserves the randomized comparison. The phrase “among participants with follow-up data” also indicates that outcome availability matters. If some randomized participants lack follow-up measurements, an analysis limited to observed follow-up data may not include everyone assigned. The missing-data method and the number of participants with available outcome data are not reported in the registry record, so the practical analysis population and any possible impact of missingness cannot be assessed.

Uncertainty and statistical significance. General: a confidence interval describes a range of values compatible with the data and the statistical procedure used. Its width conveys precision; a broad interval indicates greater uncertainty than a narrow one. A p-value addresses compatibility with a specified null model, but it does not measure clinical importance or the probability that a treatment works. No confidence intervals or p-values for the primary outcome are reported in the registry record, so neither precision nor statistical significance of the primary comparison can be evaluated.

Planning illustrations. The record describes a planning illustration based on an observed effect, using a two-sided significance level of 0.05, equal allocation between two arms, and a normal approximation. It says the effect to detect is a stated fraction of the observed effect. This is described as a planning illustration, not the trial’s own design calculation. The record does not provide numerical illustration results in the information available for this analysis. Such hypothetical sample-size calculations are not observed power and cannot substitute for the trial’s outcome estimates.

Over-dispersion and count outcomes. General: over-dispersion occurs when count variability is greater than a model assumes. If present, an analysis that ignores it may understate uncertainty. The registry’s listed primary outcome is continuous, and the available record does not specify a count-outcome model or report a test for over-dispersion. No claim about over-dispersion in this trial can therefore be made.

10. Multiplicity, Missing Data and Analysis Populations

The primary outcome has assessments at baseline, 3 months, and 6 months. The registry record explicitly indicates that it is not reduced to one comparison because it has several categories or time points. When a study examines multiple outcomes, time points, groups, or analyses, general statistical practice recognizes a multiplicity issue: the chance of at least one apparently unusual result can increase as the number of comparisons grows. Researchers may prespecify a primary contrast, adjust inference, or distinguish confirmatory from exploratory analyses. The multiplicity strategy for this trial is not reported in the registry record.

The registry lists three outcome measures and 18 analyses, but does not identify all contrasts, their hierarchy, or any adjustment procedure. It is therefore not possible to determine which analyses were intended as primary beyond the stated WOMAC-PF endpoint, or how to interpret any collection of comparisons. No primary-outcome comparison results are reported, so multiplicity-adjusted or unadjusted inferences cannot be evaluated.

The primary outcome description says an intention-to-treat approach was used among participants with follow-up data. General: intention-to-treat concerns analysis according to randomized assignment, while missing-data methods concern how unavailable measurements are handled. The record does not report the amount or pattern of missing outcome data, reasons for missingness, imputation method, sensitivity analyses, or the number analyzed at each assessment. It also does not provide enough detail to determine whether all randomized participants with missing follow-up were represented in the analysis.

The record’s stated population wording should therefore be read alongside the lack of follow-up and missing-data details. The analysis population and the robustness of results to missing data are not 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 5% reporting threshold.

Most frequent serious adverse event terms

Most frequent non-serious adverse event terms

Serious events with the highest arm-level rate: fall (2.1%), musculoskeletal and connective tissue disorder (2.1%), thromboembolic event (2.1%), urinary tract infection (2.1%), wound infection (2.1%).

For serious adverse events, the registry lists affected counts of 5 in the clinic-based outpatient exercise group, 4 in the community-based exercise group, and 5 in wait-listed usual medical care. The corresponding at-risk denominators are 96, 96, and 48. For other adverse events, the listed affected counts are 39, 42, and 22, respectively, with those same denominators. Deaths are recorded as 0 in each group.

These are counts, not adjusted comparisons. They do not by themselves show whether the groups differed in risk, and no new rates or contrasts should be inferred from them. The registry record does not report event-level timing, relatedness to the intervention, severity beyond the serious-event classification, or the method used to determine whether events were caused by treatment.

Listed serious-event terms include Fall, Musculoskeletal and connective tissue disorder, Thromboembolic event, Urinary tract infection, and Wound infection, each at 2.1%, as well as Gastroesophageal Reflux Disease at 1.0%. The denominator and reporting unit for these percentages are not reported in the registry record. The terms therefore offer a limited description of recorded events, not a basis for comparing groups or attributing causation.

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

The registry record establishes that the study was designed to compare clinic-based exercise and community-based exercise with wait-listed usual medical care after total knee replacement. It identifies WOMAC-PF as the primary patient-reported physical-function outcome and gives its scale, direction, and assessment timeframe. It also records selected safety counts. These details clarify what the trial set out to study and how the primary measure is interpreted.

The record does not report the comparative WOMAC-PF results. There are no group means, standard deviations, between-group estimates, confidence intervals, or p-values for the primary outcome in the registry information. As a result, the evidence available does not establish the size or direction of a difference, or how precisely such a difference was estimated. The absence of a reported result is not evidence that groups were equivalent or that an intervention had no effect.

Similarly, the safety counts are descriptive and do not identify cause or demonstrate a difference in risk. The listed serious-event percentages lack a reported denominator or reporting unit, which limits their interpretation. The study’s stated interest in physical activity, patient response, and safety is not a substitute for outcome-specific findings.

General: a clinical trial result is most informative when the estimated effect is considered together with its uncertainty, outcome definition, analysis population, and missing-data handling. Those comparative details are not reported in the registry record for the primary endpoint. The most defensible interpretation is therefore limited: the study design and measures are described, but the primary efficacy question cannot be answered from the recorded results.

13. Why This Trial Matters Statistically

This trial raises a useful statistical question about how exercise approaches are evaluated after total knee replacement: the comparison is not just between two exercise settings, but also against a wait-listed usual-care group. The primary endpoint is a patient-reported measure of physical function, while the registry also identifies a performance-based composite as a secondary outcome. These measures can represent different aspects of function, so clearly distinguishing their roles is important when interpreting a study.

The WOMAC-PF endpoint is measured at multiple time points, and its direction is explicit: higher scores indicate worse function. Those features make the estimand and contrast especially important. A reader would need to know whether the target comparison concerns follow-up scores, changes from baseline, or another prespecified summary, as well as how repeated observations and incomplete follow-up were handled. Those analysis details are not reported in the registry record.

The record also illustrates why design details and outcome evidence should be kept separate. Randomization describes the assignment method, and the intervention descriptions explain the broad treatment contrast. Neither provides the missing comparative estimates or their precision. Likewise, event counts provide safety context but do not establish causality or comparative risk.

Statistically, the trial matters as a case where the research question and outcome definitions are identifiable, while the available registry information does not disclose the primary comparison. That distinction prevents readers from treating a completed trial or a detailed protocol description as proof of a particular result. Interpretable reporting requires estimates, uncertainty, analysis populations, and transparent accounting for missing observations and multiple comparisons.

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 this trial is that comparative primary-outcome results are not reported in the registry record. Without group summaries and an estimate of the difference with its uncertainty, the magnitude, direction, and precision of the primary comparison cannot be assessed. The record also does not identify a threshold for an important change in WOMAC-PF.

Important analysis details are not reported in the registry record: the statistical model, the specific contrasts, baseline adjustment, handling of repeated measurements, multiplicity strategy, and any sensitivity analyses. Although the primary outcome description states that an intention-to-treat approach was used among participants with follow-up data, the number with outcome data at each assessment, reasons for missingness, and missing-data method are not reported.

Single masking is recorded, but the masked party or parties are not reported. Allocation concealment and recruitment flow are also not reported. The registry does not provide the participant characteristics or detailed eligibility criteria needed to judge how closely the enrolled population represents a particular clinical population.

The exercise descriptions specify frequency and duration but do not fully report the exercise content or adherence. Safety information is limited to group counts and selected serious-event terms; the relationship of events to the intervention and the denominator behind the listed percentages are not reported. These gaps limit both treatment-effect interpretation and assessment of how broadly the findings might apply.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Comparison of Treatments Following Total Knee Replacement — NCT02237911.
• Registry record last updated 2019-03-11; status last verified 2018-11.
• Results first posted 2019-03-11.
• 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 a completed randomized, single-masked, parallel-group study sponsored by the University of Pittsburgh, with enrollment of 240. It compares clinic-based outpatient exercise and community-based exercise with wait-listed usual medical care following total knee replacement. The exercise programs are described as occurring twice per week during 3 months, with sessions of about 60 minutes.

The primary endpoint is WOMAC-PF, a patient-reported physical-function measure assessed at baseline, 3 months, and 6 months; higher scores indicate worse function. A performance-based composite is listed as a secondary outcome. The registry records serious and other adverse-event counts and zero deaths in each group.

Comparative primary-outcome estimates and their precision are not reported in the registry record. Details of the statistical model, missing-data handling, multiplicity approach, and masking are also unavailable.