This page provides an independent statistical analysis and educational interpretation of publicly reported results. ClinicalTrials.gov provides the official trial registry record. Numerical trial results on this page are restricted to the results posted in the ClinicalTrials.gov record; calculations added by Clinical Biostats are labelled as such.
1. Trial at a Glance
This page covers the registry results for Therapeutic Effect of Two Muscle Strengthening Programs in Patients With Patellofemoral Pain Syndrome (NCT04011436), a randomized na study. The primary outcome is Assessment of Change in Pain and Function Before and After Treatment With Kujala´s Test: Presented as Percentages and 95% Confidence Interval..
| Feature | Registry value |
|---|---|
| ClinicalTrials.gov identifier | NCT04011436 |
| Phase | NA |
| Condition | Patellofemoral Pain Syndrome |
| Allocation | Randomized |
| Design model | Parallel |
| Masking | Triple |
| Enrollment | 40 |
| Arms in the primary outcome | n/a |
| Lead sponsor | Universidad Nacional de Colombia |
| Results posted | Yes |
2. Clinical Question
Population
People aged 15 to 40 years with a clinical diagnosis of patellofemoral pain syndrome and mild to moderate physical activity. The study description identifies participants as non-athletic and from Bogota, Colombia.
Intervention
A strengthening program targeting the core, hip and knee. The registry describes 28 exercises over eight weeks, with each session lasting 45 to 60 minutes and including warm-up, strengthening, balance and stretching.
Comparator
A strengthening program targeting the hip and knee, without the core component. The registry describes 24 exercises over eight weeks; the sessions also lasted 45 to 60 minutes and included warm-up, strengthening, balance and stretching.
Primary question
How did pain and function, assessed with the Kujala test, differ between the two exercise groups? The registry describes assessment before and after treatment but identifies baseline as the only time point prespecified for reporting. A comparative treatment estimate is not reported in the registry record.
The central comparison is between two active exercise programs rather than between exercise and no treatment. It therefore concerns the addition of core strengthening to a program that already targets the hip and knee. The registry describes a randomized controlled trial and reports enrollment of 40 participants. Its primary outcome description concerns pain and function, while the listed secondary outcomes concern patellofemoral alignment, strength, balance and physical activity. The registry record does not report an outcome estimate establishing how the groups compared after treatment.
3. Trial Design
The registry describes a randomized, triple-masked, parallel-group controlled trial of two muscle strengthening programs for patellofemoral pain syndrome. The study status is completed, with enrollment of 40. The record lists Universidad Nacional de Colombia as the sponsor. The study start date is 2018-08-15 and primary completion is dated 2019-01-13. The phase is listed as not applicable.
Participants were assigned to a program of core, hip and knee exercises or to a program of hip and knee exercises. Both groups completed their programs during eight weeks. The registry describes 28 exercises for the core, hip and knee group and 24 exercises for the hip and knee group. Sessions lasted 45 to 60 minutes and included warm-up, strengthening, balance and stretching. Because both groups received exercise, the design evaluates the two programs against one another, not exercise against an untreated control.
Triple masking is the registry's description of masking; which specific roles were masked is not reported in the registry record. The method used to generate the random assignment sequence, conceal allocation before assignment, handle adherence, or define the analysis population is also not reported in the registry record. These details matter when judging how assignment was implemented and whether the results could be affected by treatment knowledge or departures from the assigned programs.
The Kujala test was named as the primary measure for pain and function. The registry states that assessment occurred at baseline and after treatment, while identifying baseline as the only time point prespecified for reporting. The outcome results needed to assess the groups' post-treatment comparison 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.
Overall Study
| Stage | Core, Hip and Knee. | Hip and Knee |
|---|---|---|
| STARTED | 20 | 20 |
| COMPLETED | 19 | 19 |
| NOT COMPLETED | 1 | 1 |
Analysis population for the primary outcome, as defined in the registry: Group A (core, hip and knee) completed a 28 exercises and Group B (hip and knee) completed a 24 exercises both groups during 8 weeks, each exercise session lasted 45 to 60 minutes and included warm up, strengthening, balance and stretching.
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.
| Characteristic | Unit | Core, Hip and Knee. | Hip and Knee | Total |
|---|---|---|---|---|
| Participants analysed | 20 | 20 | 40 | |
| Age, Categorical: Age – <=18 years | Participants | 2 | 2 | 4 |
| Age, Categorical: Age – Between 18 and 65 years | Participants | 18 | 18 | 36 |
| Age, Categorical: Age – >=65 years | Participants | 0 | 0 | 0 |
| Age, Continuous | years | 32.5 (25.5 to 38) | 29 (25 to 36.5) | 30.75 (25.25 to 37.25) |
| Sex: Female, Male: Female | Participants | 18 | 18 | 36 |
| Sex: Female, Male: Male | Participants | 2 | 2 | 4 |
| Race and Ethnicity Not Collected | Participants | — | — | 0 |
| Region of Enrollment: Colombia | Participants | 20 | 20 | 40 |
| Height | cm | 160 (156.5 to 167) | 159.5 (154 to 163) | 159.75 (155.25 to 165) |
| BMI | kg/m^2 | 25.4 (21.5 to 27.9) | 23.8 (22.3 to 25.2) | 24.6 (21.9 to 26.55) |
| Fat Percent | percent | 35.4 (28.9 to 40.4) | 35.4 (24.5 to 38.7) | 35.4 (26.7 to 39.6) |
| Muscle Percent | percent | 26.9 (24.5 to 28.9) | 26.2 (24.6 to 29) | 26.6 (24.6 to 29) |
| Visceral Fat Percent | percent | 6 (3.5 to 7.09) | 5 (4 to 6) | 5.5 (3.8 to 6.5) |
| The International Physical Activity Questionnaire, Long Form (27-item self-reported measure) | total minutes of physical activity | 3003 (1116 to 4638) | 1617 (944 to 6138) | 2310 (1030 to 5388) |
6. Primary Endpoint
The registry lists the primary outcome as Assessment of Change in Pain and Function Before and After Treatment With Kujala´s Test: Presented as Percentages and 95% Confidence Interval., measured over The next table shows the distribution of the 13 domains of the Kujala´Test by intervention group at baseline (Time point 1, one day before intervention). "Assessed at baseline and after treatment, only baseline pre-specified to be reported"..
| Element | Registry entry |
|---|---|
| Result type | Number |
| Measure of spread | 95% Confidence Interval |
| Unit | percentage of participants |
| Endpoint classification | Binary Endpoint |
The primary outcome is described as assessment of change in pain and function using the Kujala test. This scale is intended to assess pain and function in people with disorders of the patellofemoral joint. It has 13 questions, with three to five response options for each question. Depending on the question, responses are scored from 0 to 5 or 0 to 10. A total score can range from 0 to 100: 0 represents the worse functional health condition and 100 represents no alteration and optimal condition, as described in the registry.
The Kujala test is relevant to the study question because the interventions aim to address symptoms and function in people with patellofemoral pain syndrome. A change measure could describe how scores move between assessment points, while a comparison between groups could address whether the pattern differs across the two programs. Those are distinct questions: a change within either group does not by itself establish a difference between groups.
The registry labels the outcome as percentages with 95% confidence intervals and describes a baseline distribution of the 13 domains by intervention group. It also states that assessment was made before and after treatment, but baseline was the only time point prespecified for reporting. The registry record does not report the numerical domain results or a post-treatment estimate of change.
7. Why No Re-analysis Is Shown
8. Statistical Interpretation
The registry describes a randomized comparison of two exercise programs and identifies pain and function measured with the Kujala test as the primary outcome. It does not report numerical results for that outcome in the record summarized for this analysis. In particular, the record describes baseline domain distributions but does not supply the percentages or confidence intervals, and it states that baseline was the only time point prespecified for reporting. There is therefore no posted estimate with which to quantify a post-treatment difference between the programs.
This distinction limits what can be concluded. The study description gives the intended intervention, comparator, duration and outcome measure. Those design details do not reveal the size, direction or precision of the outcome contrast. Without reported post-treatment results, it is not possible to describe whether either group had a particular amount of change or whether the groups differed on the Kujala measure. No conclusion about treatment benefit or lack of benefit follows from the absence of those figures.
The registry describes the Kujala outcome as percentages with 95% confidence intervals. A confidence interval is a statistical range expressing uncertainty around an estimate under the method used to calculate it. Its width can help readers judge precision, but it does not substitute for the estimate itself or resolve limitations in the design or reporting. Since neither the actual percentages nor their intervals are reported in the record, that precision cannot be evaluated for the primary outcome.
The record reports enrollment of 40 and lists 20 participants at risk in each group for the adverse-event summaries. These figures describe the study's size and the denominators used for those safety counts; they do not provide the missing primary endpoint results. The registry lists seven outcome measures and seven analyses, but the named secondary outcomes also do not include numerical results in the registry record for interpretation. The details of any statistical adjustment, missing-data handling or analysis population are not reported in the registry record.
The appropriate reading is consequently descriptive rather than comparative: the trial was designed to compare two active strengthening programs, but the registry record does not provide the endpoint results needed to estimate that comparison. The completed status indicates that the study is recorded as completed; it does not establish that all outcomes were posted or that the intervention groups had a particular result.
9. Statistical Methods Explained
Several statistical ideas help frame this trial, although the registry record does not report enough outcome data to evaluate a treatment contrast. The record identifies random allocation, triple masking and a parallel design. Random allocation is intended to make assigned groups comparable on average at the start of a study, including on factors that may not have been measured. It does not ensure identical groups in a trial, and it does not replace reporting the baseline characteristics or outcome results. Those details are not reported in the registry record used.
What does a parallel-group comparison estimate?
In a parallel-group design, participants remain in their assigned group while the programs are compared. Here the groups were assigned different exercise programs: core, hip and knee strengthening versus hip and knee strengthening. The comparison of interest is the difference in outcome between those programs, not simply whether scores changed within either group. Improvement within a group can reflect the assigned program, changes over time, measurement variation or other influences. A between-group estimate is needed to evaluate the relative outcomes of the two assigned programs.
The record reports that the primary outcome was assessed at baseline and after treatment, but says that only baseline was prespecified for reporting. This creates an important reporting limitation: baseline measurement describes the groups before the intervention period, whereas a treatment comparison generally requires post-treatment information or an appropriate estimate of change. The post-treatment Kujala results and any group contrast are not reported in the registry record.
How should percentages and confidence intervals be read?
The primary outcome description says that results are presented as percentages with 95% confidence intervals. A percentage expresses a quantity relative to a denominator, but the precise calculation for each Kujala domain is not further explained in the registry record. A confidence interval represents uncertainty around an estimate under the statistical assumptions and procedure used to construct it. A narrower interval generally conveys greater precision than a wider one, while neither interval width nor its position establishes that a program is effective. The actual percentages and intervals are not reported, so the primary endpoint's estimated values and precision cannot be assessed.
The Kujala scale has 13 questions, each with three to five response options, and different questions use scores from 0 to 5 or 0 to 10. The total score ranges from 0 to 100, with lower values indicating worse functional health and the highest value indicating no alteration and optimal condition, according to the description. Understanding the scale's direction is necessary to interpret a score change. However, the registry's presentation as percentages by domain should not be treated as a reported total-score change unless the record explicitly supplies that result; it does not do so.
What do the design labels tell readers?
Randomized means participants were assigned at random, but the sequence-generation and allocation-concealment procedures are not reported in the registry record. Triple masking indicates that masking was described, but the record does not identify the masked roles. The parallel design indicates that the groups were compared alongside one another during the study. These labels do not disclose adherence, crossover, withdrawals or whether analysis followed original assignment; these details are not reported in the registry record.
The study enrolled 40 participants, and the adverse-event summaries list 20 at risk in each group. Enrollment is not a substitute for an outcome-specific denominator. The numbers contributing to each Kujala domain, the handling of incomplete questionnaires and the analysis population are not reported. If outcome data are missing, the analysis method can affect estimates and uncertainty; how missing values were handled is not reported.
What is the role of planning assumptions?
The record describes a sample-size planning illustration based on an observed effect, with a two-sided significance level of 0.05, equal allocation, a normal approximation and effects expressed as stated fractions of the observed effect. It distinguishes participant counts per arm for outcomes other than time-to-event outcomes. These are planning conventions, not evidence about the study's observed outcome and not the study's original design justification. Numerical planning results and the trial's own sample-size justification are not reported in the registry record. No planning illustration should be read as observed power or as an outcome estimate.
Over-dispersion is a general statistical concern when observed variability exceeds what a chosen model assumes. If present, a model that ignores it can understate uncertainty and produce overly narrow confidence intervals. The registry record does not identify an over-dispersion assessment or a particular model for the Kujala outcome, so it is not possible to say whether this issue was evaluated in this trial. More broadly, the record does not report the complete statistical analysis plan, the tests used for the primary comparison, or any adjustment for multiple outcomes.
10. Multiplicity, Missing Data and Analysis Populations
The registry records seven outcome measures and seven analyses. It names the Kujala pain and function assessment as the primary outcome and lists secondary measures for patellofemoral misalignment by Q angle, core strength by McGill's exam, quadriceps and gluteus strength by squat's test, static balance by single-leg stance, and physical activity measured with the International Physical Activity Questionnaire-Long Form. The record's count of outcome measures exceeds the number of secondary outcomes named in the registry record; further outcome details are not reported in the registry record.
When a study examines multiple outcomes or analyses, the chance of obtaining at least one apparently notable result can increase. Statistical plans sometimes address this through a prespecified hierarchy or adjustment, but the registry record does not report whether any such approach was used. It also does not report a complete analysis plan or identify interim analyses. The existence of seven analyses alone does not show that results were adjusted or unadjusted, and no conclusions about multiplicity handling can be drawn.
The registry states that the Kujala measure was assessed before and after treatment but that baseline was the only time point prespecified for reporting. Numerical baseline results and post-treatment results are not reported in the registry record. The reasons for limiting reported time points, and whether other time points or outcomes were analyzed, are not reported.
Missing-data methods and analysis populations are also not reported in the registry record. The record does not state how incomplete questionnaires, withdrawals, non-adherence or other missing observations were handled. It does not specify whether the primary analysis included all randomized participants or a different set. Without these details, readers cannot assess whether the analysis preserved the benefits of random assignment or how missing observations may have affected precision and interpretation.
11. Safety Results
The registry reports serious adverse events as affected participants divided by participants at risk.
| Arm | Participants with serious adverse events | Participants at risk | Percentage |
|---|---|---|---|
| Core, Hip and Knee. | 0 | 20 | 0.0% |
| Hip and Knee | 0 | 20 | 0.0% |
Deaths
| Arm | Deaths (participants affected of at risk) |
|---|---|
| Core, Hip and Knee. | 0 of 20 |
| Hip and Knee | 0 of 20 |
Other (non-serious) adverse events
Participants with at least one non-serious event at or above the registry's 0% reporting threshold.
| Arm | Participants affected of at risk |
|---|---|
| Core, Hip and Knee. | 0 of 20 |
| Hip and Knee | 0 of 20 |
The registry's adverse-event summaries list 20 participants at risk in each group. For the core, hip and knee group, 0 participants had a serious adverse event and 0 had another adverse event; deaths were 0. For the hip and knee group, 0 participants had a serious adverse event and 0 had another adverse event; deaths were 0. No serious adverse-event terms are listed.
These counts mean that the registry reports no events in the categories recorded for either group. They do not establish that no unrecorded or unreported event occurred, and they do not show that the programs have no risk. Zero observed events in a study of this size leave uncertainty about the frequency of uncommon events. The registry record does not provide further detail about how events were solicited, how long safety follow-up continued, or whether all events were assessed for a possible relationship to the exercise programs.
Serious and other adverse events are distinct categories in the registry summary. The zero counts should be read as event reporting within those categories, not as a measure of the primary Kujala outcome. They also do not answer whether participants experienced changes in pain or function. The reported safety counts are descriptive and do not establish a comparative safety advantage between the exercise programs.
12. What the Result Does, and Does Not, Mean
The trial addresses a focused comparative question: whether a strengthening program including the core, hip and knee differs from one targeting the hip and knee in people with patellofemoral pain syndrome. The randomized, parallel-group design is suitable in principle for comparing assigned programs. The registry also provides practical intervention details, including the eight-week duration and the structure of sessions. These features explain what the investigators intended to compare.
What the registry record does not provide is the numerical primary outcome result needed to interpret the comparison. Although the Kujala test was assessed before and after treatment, the record says that only baseline was prespecified for reporting. The numerical baseline domain percentages and confidence intervals are not available in the record summarized for interpretation, and no post-treatment contrast is reported. Consequently, the direction, magnitude and precision of any difference between programs cannot be described. This absence is not evidence that the programs produced equal outcomes, nor evidence that either did or did not produce change.
The study enrolled 40 participants and reports no adverse events in the registry's serious or other adverse-event categories. Those observations describe the posted safety counts, but do not establish a general safety profile or settle the primary effectiveness question. The listed secondary outcomes could offer information about strength, alignment, balance and physical activity, but numerical results for those measures are not reported in the registry record.
Accordingly, the record supports a description of the study question, design and intended measurements, but not a conclusion about comparative clinical outcomes. Interpreting the trial would require the reported outcome estimates, their uncertainty, denominators, analysis methods and relevant missing-data information. Those details are not reported in the registry record. The registered completion status should be understood as a study-status entry, not as a substitute for outcome reporting.
13. Why This Trial Matters Statistically
This trial is statistically interesting because it compares two active programs that share hip and knee strengthening, with core strengthening as the distinguishing element. That makes the intended contrast more specific than a comparison of exercise with no exercise: the question concerns the relative outcome of adding core exercises within a broader strengthening program. The registry describes random allocation and a parallel design, which are relevant features for making that comparison.
The outcome choice also matters. The Kujala test addresses pain and function in patellofemoral disorders and includes 13 domains with response scores that vary by question. Its total score has a defined direction, from worse functional health at 0 to optimal condition at 100. Reporting the scale and its interpretation helps readers understand what investigators planned to measure. But a measure's relevance does not resolve the need for complete outcome reporting.
The registry record highlights a gap between the stated assessment schedule and the stated reporting plan: assessment was described at baseline and after treatment, while baseline alone was prespecified for reporting. Without numerical results for the primary comparison, readers cannot assess effect size or precision. This is a statistical limitation as well as a reporting limitation, because a randomized design can support a comparative estimate only when the outcome data and analysis are available.
The record lists several secondary domains, including strength, alignment, balance and physical activity. Multiple outcomes can broaden the description of a study, but also make prespecification and clear reporting of analyses important. The registry does not report whether multiplicity was addressed. The record therefore illustrates why readers need more than a design label: outcome estimates, uncertainty, analysis populations and handling of missing data are necessary to judge what a trial's data establish.
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.
A central limitation is that the registry record does not report the numerical Kujala results. The outcome description specifies percentages and 95% confidence intervals for baseline domain distributions, but those figures are not available in the registry record. Although measurement was described before and after treatment, the record says that only baseline was prespecified for reporting. As a result, the comparative post-treatment outcome cannot be evaluated.
Reporting detail is limited for the statistical analysis. The registry record does not report the method used to calculate the percentages or confidence intervals, the test or model used for a group comparison, or whether baseline values were incorporated into an adjusted analysis. It does not report the analysis population, handling of missing responses, withdrawals, adherence or protocol deviations. The method of random sequence generation, allocation concealment and the roles included in triple masking are also not reported.
The record reports enrollment of 40 and describes participants as 15 to 40 years old, non-athletic and having mild to moderate physical activity with a clinical diagnosis of patellofemoral pain syndrome. This defined study population may not represent people outside those characteristics. The registry's intervention descriptions distinguish 28 exercises from 24 exercises and report sessions of 45 to 60 minutes over eight weeks, but adherence and delivery consistency are not reported.
The registry lists seven outcome measures and seven analyses, while the registry entries available include five named secondary outcomes. The full multiplicity strategy, any interim analyses and a complete statistical plan are not reported in the registry record. Finally, the adverse-event summaries report zero events but do not describe ascertainment procedures or follow-up duration. These omissions constrain interpretation of both outcome precision and safety reporting.
15. Related Tutorials
16. Related Statistical Calculators
17. Sources
- ClinicalTrials.gov: Therapeutic Effect of Two Muscle Strengthening Programs in Patients With Patellofemoral Pain Syndrome — NCT04011436.
- Registry record last updated 2021-11-23; status last verified 2021-10.
- Results first posted 2021-11-23.
- 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.
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18. Record Summary
The registry identifies a completed randomized, triple-masked, parallel-group trial sponsored by Universidad Nacional de Colombia. It enrolled 40 participants with patellofemoral pain syndrome and compared core, hip and knee strengthening with hip and knee strengthening. The listed study dates are 2018-08-15 for start and 2019-01-13 for primary completion.
The primary measure was pain and function assessed with the Kujala test. The registry describes baseline and post-treatment assessment, while stating that baseline was the only time point prespecified for reporting. Numerical primary outcome estimates and comparative results are not reported in the registry record. Five secondary measures are named, addressing alignment, strength, balance and physical activity; their numerical results are also not reported in the record.
The adverse-event summaries list zero serious adverse events, zero other adverse events and zero deaths in each group, with 20 participants at risk in each group. The registry records seven outcome measures and seven analyses, but does not report the full statistical plan, analysis populations or missing-data methods.