Electromyostimulation and Strength Walking for Knee Injuries: Complete Statistical Analysis

1. Trial at a Glance

This page covers the registry results for Electromyostimulation and Strength Walking for Knee Injuries (NCT02065518), a randomized na study. The primary outcome is Lower Extremity Muscle Strength- Extension.

2. Clinical Question

The study is described as comparing the effects of the three added regimens with standard rehabilitation alone. Its stated areas of interest include strength, mobility, symptomatology, and quality of life. The listed primary endpoint is lower-extremity muscle strength measured for extension. The registry record describes measurements of the injured and uninjured knee, with assessments at 0, 3, 6, 9, 12, and 18 weeks.

The clinical question is therefore broader than whether one group has a higher average strength measurement at a single assessment. In a factorial design, the analysis can ask about the average contribution of NMES across walking conditions, the average contribution of strength walking across NMES conditions, and whether combining the two changes their effects. The registry record states that main and interactive effects over time were to be compared. Numerical results for those comparisons are not reported in the registry record, so the direction, size, and precision of any differences cannot be described.

3. Trial Design

This was a randomized, unmasked, factorial trial with a recorded enrollment of 78. The registry record lists the study as completed and gives a start of 2014-03 and a primary completion of 2016-08. It describes four groups: standard rehabilitation protocol (SRP) alone, NMES with SRP, strength walking with SRP, and NMES plus strength walking with SRP. Thus, the comparison includes each added regimen on the background of standard rehabilitation rather than a group receiving no rehabilitation.

The factorial structure organizes the four groups around two treatment components: NMES and strength walking. As a general explanation, a factorial design can estimate each component's average effect across levels of the other component and can examine whether the combined regimen behaves differently from what would be expected from the components considered separately. The registry record states that main and interactive effects over time were planned for comparison. The exact statistical model and the way those effects were to be estimated are not reported in the registry record.

All participants were described as receiving standard rehabilitation, a physical therapy protocol at the WRNMMC and MGMCSC sites. The NMES groups were described as using a portable device for four 30-minute stimulation sessions per week for 12 weeks. The strength-walking groups were described as following a home-based, pedometer-driven walking program, with a weighted exercise vest introduced at week 7. Further protocol detail is not reported in the registry record.

Assessments were planned over 18 weeks. The design is unmasked, so participants and relevant study personnel were not described as blinded to assigned treatment. The process used to generate the random allocation, conceal assignments, or manage adherence is 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.

Overall Study

Reasons for not completing this period:

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 Lower Extremity Muscle Strength- Extension, measured over 0, 3, 6, 9, 12, and 18 weeks.

The primary endpoint is lower-extremity muscle strength for extension, measured in kilograms. The registry record describes measurement of extensor knee strength in both the injured and uninjured knee using a handheld dynamometer. Assessments are listed at 0, 3, 6, 9, 12, and 18 weeks.

As a general measurement concept, a dynamometer quantifies force during a standardized strength test. A continuous measure such as strength can be summarized by a mean and a measure of variability, and it can be compared between treatment groups or across repeated assessments. The registry record identifies the planned summary as a mean with standard deviation. The standard deviation describes variation among measurements; it is not the same as the uncertainty in an estimated group mean.

Strength is used as an outcome because the study's stated purpose includes comparing effects on strength as well as mobility, symptoms, and quality of life. Repeated assessment can describe how a measured outcome changes over the study period, while comparisons between groups can address whether those patterns differ by regimen. However, numerical strength results, group means, standard deviations, and treatment comparisons are not reported in the registry record. The endpoint description alone cannot establish whether strength changed or whether any group differed from another.

7. Why No Re-analysis Is Shown

8. Statistical Interpretation

9. Statistical Methods Explained

The design is described as randomized and factorial. Randomization is intended, as a general statistical principle, to reduce systematic differences between assigned groups at the start of a trial. It does not guarantee that groups will be identical, and it does not remove the need to report how allocation was generated, how many participants were analyzed, and what adjustment or modeling was used. Those details are not reported in the registry record.

What the factorial structure asks

The four arms combine standard rehabilitation with neither added component, NMES, strength walking, or both added components. A factorial analysis can separate two kinds of questions. A main-effect contrast asks about one component averaged across the presence or absence of the other component. An interaction asks whether the effect of one component depends on the other. If interaction is present, an average main effect may not fully describe the pattern across the individual regimens. The registry record says that main and interactive effects over time were to be compared, but the analysis model, contrasts, and results are not reported in the registry record.

Repeated measurements and continuous outcomes

Strength is a continuous outcome expressed in kilograms, and the registry record specifies a mean and standard deviation. The listed assessments occur at 0, 3, 6, 9, 12, and 18 weeks. Measurements from the same participant are generally related rather than independent: a person's measurement at one visit can be associated with measurements from other visits. As a general statistical matter, an analysis of repeated measurements needs to account for that dependence if it estimates a trajectory or compares changes over time. The method used to do so is not reported in the registry record.

A mean describes the center of a set of measurements. A standard deviation describes their spread around the mean. A confidence interval, when reported, describes the precision of an estimated quantity under the assumptions of the analysis; it is not a range containing a fixed proportion of individual participant measurements. No confidence intervals or numerical strength summaries are reported in the registry record, so the precision of any strength comparison cannot be assessed.

As a general point, a model for repeated outcomes may estimate differences between groups at particular visits, an overall group pattern, or differences in change over time. Those quantities answer related but nonidentical questions. A clear interpretation depends on knowing which quantity was prespecified and how it was estimated. The registry record does not report the exact estimand, model specification, or planned contrast for the primary outcome.

Multiplicity and interpretation of tests

The study includes several groups, repeated assessments, a primary outcome, and listed secondary outcomes. As a general statistical concept, testing many hypotheses can increase the chance of obtaining at least one apparently unusual result even when no underlying effect exists. Multiplicity methods can control or characterize that issue, but they depend on which hypotheses were grouped together and what inferential goal was chosen. A multiplicity strategy, testing hierarchy, or distinction between confirmatory and exploratory analyses is not reported in the registry record. Numerical test results are also not reported, so no p-value interpretation is possible.

Dispersion, model assumptions, and precision

For continuous outcomes, the choice of statistical model can depend on the distribution of measurements and residuals, the handling of repeated observations, and the presence of unusual values. General model checking examines whether assumptions are sufficiently reasonable for the chosen analysis. Over-dispersion is a concern mainly in models for counts when variability exceeds what the model allows; it is not a direct substitute for examining the spread and distribution of this continuous strength outcome. The registry record does not report diagnostics, transformations, or the handling of influential observations.

Precision depends on the amount of information contributing to an estimate, including the analyzed sample size and variability. The enrollment count does not by itself establish how many participants contributed measurements at each visit or to each comparison. Endpoint-specific analyzed counts and missing-measurement patterns are not reported in the registry record. No statistical analysis results are reported, so neither significance nor precision can be inferred from the design description or enrollment alone.

10. Multiplicity, Missing Data and Analysis Populations

The registry record lists a primary strength endpoint measured repeatedly and several secondary outcomes: overall pain severity, knee pain after performance testing, activities-of-daily-living knee symptoms, and activity limitation. Multiple outcomes, treatment contrasts, and assessment times can create multiple opportunities to test hypotheses. As a general statistical principle, multiplicity matters because the chance of at least one false-positive finding can increase when many tests are considered. The record does not report a correction method, testing hierarchy, or which comparisons were designated confirmatory.

Missing-data handling is also important in a study with repeated assessments. If some participants do not contribute measurements at every visit, the analysis can depend on how much data are missing, why they are missing, and what assumptions the statistical method makes about those missing values. The registry record does not report missing-data counts, reasons for missingness, imputation methods, or sensitivity analyses.

Analysis populations are not defined in the registry record. It is not reported whether the primary analysis included all randomized participants, only participants with available measurements, or another specified group. The safety group counts do not establish the endpoint-specific analysis population. No statistical analyses are listed, and outcome estimates or test results are not reported. Consequently, the available record does not permit assessment of how multiplicity, incomplete follow-up, or analysis-population choices affected the reported results.

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.

The registry safety entries list 0 serious adverse events and 0 other adverse events in each of the four groups. The numbers at risk are 19 for standard rehabilitation, 19 for NMES with standard rehabilitation, 20 for strength walking with standard rehabilitation, and 20 for the combined regimen. Deaths are listed as 0 in every group. No serious adverse-event terms are listed.

These are counts in the registry record, not estimates of comparative risk. A count of zero recorded events does not by itself show that an intervention is free of risk. Its interpretation depends on the duration and completeness of safety monitoring, how events were defined and collected, and how much information was available. Those details are not reported in the registry record.

The figures also do not establish whether events occurred outside the categories represented in these entries or whether all participants contributed complete safety follow-up. The record does not report a comparative statistical analysis of adverse events. The appropriate reading is limited to the posted counts: no serious events, other events, or deaths are recorded in these group entries.

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

The registry record describes a randomized factorial comparison of four rehabilitation regimens for knee injury, with all groups receiving standard rehabilitation. The primary outcome is knee-extension muscle strength measured in kilograms using a handheld dynamometer, with assessments scheduled from baseline through 18 weeks. The design addresses the added contributions of NMES and strength walking, their combination, and possible changes in effects over time.

Those design features clarify what the trial was intended to investigate, but they do not provide the results. Numerical strength measurements, between-group estimates, uncertainty intervals, and statistical tests are not reported in the registry record. The record therefore does not establish the direction or magnitude of any difference, the precision of an estimate, or whether a result met a statistical threshold.

Nor does the absence of numerical results establish that the groups were the same. Similarity, difference, and uncertainty require estimates from the observed data. Likewise, a randomized design alone does not show that allocation was successfully implemented or that missing data and adherence were handled in a particular way; those details are not reported in the registry record.

The listed secondary outcomes indicate that symptoms and daily activities were also of interest, but their results are not reported in the registry record. Safety entries record zero serious adverse events, zero other adverse events, and zero deaths in each group. Those counts should be read as recorded event counts, not proof that the interventions carry no risk.

The most defensible conclusion is about the scope of the investigation: it was designed to compare added rehabilitation components on a standard-care background and to examine strength over time. Claims about treatment benefit, lack of benefit, equivalence, or harms go beyond the numerical information recorded.

13. Why This Trial Matters Statistically

This trial is statistically notable because its factorial structure addresses two rehabilitation components within one four-group design. Rather than treating the combined regimen only as a separate option, a factorial framework can ask whether NMES and strength walking have distinct average contributions and whether their combination changes the pattern. That makes interaction an important part of the question: component effects need not be simply additive.

The repeated strength assessments add another dimension. A comparison at one visit asks a different question from a comparison of trajectories across visits. A time-dependent effect may be missed or obscured by focusing on a single measurement, while repeated measurements require methods that account for within-participant dependence. The registry record identifies the schedule and says effects over time were to be compared, but does not report the analysis used or its findings.

The trial also illustrates why a registered design is not a substitute for posted outcome estimates. Enrollment and planned measures describe the scope of the study, but they do not reveal group means, variability, precision, or the amount of missing follow-up. Without those results, readers cannot assess the strength of evidence for the primary or secondary questions.

Finally, the zero event counts require a careful distinction between observed counts and broader safety conclusions. The record documents the counts in each group, but does not supply enough information to characterize monitoring completeness or comparative risk. The statistical value of this record is therefore chiefly in making the design and intended questions visible; evaluation of the findings requires numerical outcomes and analysis details that are not reported in the registry record.

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 from the registry record is that numerical outcome results are not reported. The primary strength outcome is described, but group means, standard deviations, treatment contrasts, and uncertainty estimates are absent. The record therefore does not support assessment of effect direction, magnitude, or precision.

The analysis plan is also not reported in the registry record. The trial is labeled randomized and factorial, and the description says that main and interactive effects over time were to be compared, but the model, estimands, contrasts, and inferential procedures are not given. Allocation generation and concealment procedures are not reported. The record identifies masking as none, which is relevant context for interpreting outcomes and their collection.

Although 78 participants were enrolled, analyzed counts by endpoint and assessment time are not reported. Missingness, adherence, protocol deviations, and analysis-population definitions are also not reported in the registry record. These omissions prevent evaluation of whether all randomized participants contributed to the primary comparison and how incomplete follow-up may have influenced estimates.

The study lists multiple secondary outcomes and repeated assessments, but a multiplicity strategy is not reported. The available safety counts show no recorded events in the listed categories, but monitoring duration and completeness are not described in the registry record. Further detail on eligibility, baseline characteristics, and the full intervention procedures is also not reported. These limitations constrain interpretation of both clinical relevance and statistical reliability.

15. Related Tutorials

16. Related Statistical Calculators

17. Sources

• ClinicalTrials.gov: Electromyostimulation and Strength Walking for Knee Injuries — NCT02065518.
• Registry record last updated 2019-08-28; status last verified 2018-10.
• Results first posted 2019-08-14.
• 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 identifies NCT02065518, titled Electromyostimulation and Strength Walking for Knee Injuries, as a completed, randomized, unmasked factorial trial with enrollment of 78. It compares standard rehabilitation alone with NMES, strength walking, or both added to standard rehabilitation for military members with knee injury.

The primary outcome is lower-extremity muscle strength for extension, measured in kilograms with a handheld dynamometer in the injured and uninjured knee. Assessments are listed at 0, 3, 6, 9, 12, and 18 weeks. The registry record also lists outcomes concerning pain, symptoms, and activity limitation.

Safety entries list no serious adverse events, other adverse events, or deaths in any group. Numerical primary and secondary outcome results, statistical analyses, missing-data handling, and analysis-population definitions are not reported in the registry record.