The Munich Knee Questionnaire: Development and Validation of a New Patient-Reported Outcome Measurement Tool for Knee Disorders Marc Beirer, M.D., Nico Fiedler, C.M., Stephan Huber, M.D., Marcus Schmitt-Sody, M.D., Stephan Lorenz, M.D., Peter Biberthaler, M.D., and Chlodwig Kirchhoff, M.D.

Purpose: To develop and validate an all-purpose patient-reported outcome questionnaire for a patient-based follow-up examination regarding knee disorders. Methods: Each scale of the Knee Injury and Osteoarthritis Outcome Score (KOOS), International Knee Documentation Committee (IKDC) score, Lysholm knee score, Western Ontario Meniscal Evaluation Tool (WOMET) score, and Tegner score was analyzed, and after matching of the general topics, the dedicated items underwent a fusion to the final Munich Knee Questionnaire (MKQ) item and a score comprising 33 items was created. In a prospective clinical study, we evaluated validity, reliability, and responsiveness in 152 physical active patients (75 women and 77 men; mean age, 47 years) with traumatic as well as degenerative knee disorders. Results: Test-retest reliability was substantial, with intraclass correlation coefficients of at least 0.91. Construct validity and responsiveness were confirmed by correlation coefficients of 0.78 to 0.86 (P ¼ .01) and 0.41 to 0.71, respectively. Correlation coefficients of the original scores (KOOS, IKDC, Lysholm, WOMET, and Tegner) and the scores calculated from the MKQ were between 0.80 and 0.91 (P ¼ .01). Conclusions: The MKQ is a reliable and valid patient-reported outcome questionnaire for assessing knee function. It seems to enable the calculation of the original items of the KOOS, IKDC score, Lysholm knee score, WOMET score, and Tegner score. Clinical Relevance: The MKQ facilitates the comparison of treatment results in knee disorders and allows the evaluation of treatment efficacy. Identified inadequate treatment concepts could be eliminated, leading to increased patient satisfaction and optimized quality of health care.

P

atient-reported outcome (PRO) questionnaires in general are suitable for outcomes research in patients with knee disorders because of their high validity as additional tools to clinician-assessed parameters for a comprehensive evaluation of clinical outcome.1-3 No need to travel long distances for follow-up examinations in outpatient clinics and no need for the presence of a physician reduce the logistic effort and increase the response rate, leading to an increasing use of selfassessment questionnaires in outcomes research.4 In this context numerous authors have reported on outcome measurement tools after knee surgery.5-11 From the Departments of Trauma Surgery (M.B., N.F., S.H., P.B., C.K.) and Orthopaedic Sports Medicine (S.L.), Klinikum rechts der Isar, Technical University of Munich, Munich; and Medical Park Bernau Chiemsee (M.S-S.), Bernau am Chiemsee, Germany. The authors report that they have no conflicts of interest in the authorship and publication of this article. Received December 31, 2013; accepted February 19, 2015. Address correspondence to Marc Beirer, M.D., Department of Trauma Surgery, Klinikum rechts der Isar, Technical University of Munich, Ismaningerstrasse 22, 81675 Munich, Germany. E-mail: [email protected] Ó 2015 by the Arthroscopy Association of North America 0749-8063/143/$36.00 http://dx.doi.org/10.1016/j.arthro.2015.02.026

However, there is no consensus in the literature about a universal tool for evaluation of knee function. Because of the large number of questionnaires focusing on knee disorders, the direct comparability of different follow-up studies is limited. Consequently, the risk of maintaining inadequate treatment concepts is increased, leading to reduced treatment quality and decreased patient satisfaction.12 The purpose of this prospective study was to develop and validate an all-purpose PRO questionnaire for a patientbased follow-up examination regarding knee disorders. We hypothesized that the Munich Knee Questionnaire (MKQ) would allow for a qualitative self-assessment of the Knee Injury and Osteoarthritis Outcome Score (KOOS),6 International Knee Documentation Committee (IKDC) score,13 Lysholm knee score,14 Western Ontario Meniscal Evaluation Tool (WOMET) score,11 and Tegner score.15

Methods Development of Questionnaire A systematic review of the literature was performed to identify valid and commonly used instruments

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regarding follow-up examinations in the field of knee disorders. The PubMed Web site was searched for kneespecific terms (knee, surgery, joint, lower extremity) combined with psychometric (follow-up, validity, reliability, responsiveness) and instrument-specific terms (self-reported, patient-based, measurement tool, outcome measure, questionnaire). The KOOS, IKDC score, Lysholm knee score, WOMET score, and Tegner score were identified as frequently used and valid measurement tools. To achieve a comprehensive tool, evaluation of the knee function activity of the patient seems to be crucial. Therefore the Tegner score as frequently used instrument to assess the activity level was included. To ensure content validity of the MKQ, each scale (KOOS, IKDC score, Lysholm knee score, WOMET score, and Tegner score) was analyzed for items addressing either general topics or specific items. Subsequently, matching of the general topics was performed, and the dedicated items underwent a fusion to the final MKQ item. Specific items that had no corresponding item in the other scales (e.g., instability) were incorporated without further modification. Finally, the items were allocated to 5 domains, and the weighting of each domaindin terms of the number of items allocated to each domaindwas done in parallel to the previous scales. The MKQ contains 33 items addressing 5 domains: 7 items addressing physical symptoms, 6 items addressing pain, 5 items addressing activities of daily life (ADL), 6 items regarding sports and recreational activities (SRA), and 9 items addressing physical function and kneerelated quality of life (QOL) (Appendix). The best and least symptomatic score for each item is 0; the worst is 10. The overall score is converted to a scale of 100%, where a value of 100% indicates an excellent result and a value of 0% indicates a poor result. Typical functional abilities (flexion/extension) are depicted as photographs. Patient Collective All patients who presented during the consultation hours of the senior author (C.K.) at our institution between August 2012 and July 2014 because of traumatic ligament, meniscal, or bony disorders of the knee joint, as well as degenerative knee joint disorders, were asked to participate in our study. The exclusion criteria were patients with limited legal capacity or under legal supervision and patients with psychiatric diseases, dementia, or other cognitive diseases. The study protocol was approved by our local ethics committee. Testing and Evaluation of Measurement Qualities Floor and Ceiling Effects. According to McHorney and Tarlov,16 floor and ceiling effects exist if more than

15% of patients achieve the highest or lowest possible score. Therefore we would define floor or ceiling effects to be present if more than 15% of our patient collective achieved the highest (100 points) or lowest (0 points) possible score of the MKQ. Internal Consistency. Internal consistency is defined by the degree of interrelation among the tested items.17 The subscales are based on a reflective model in which all items are defined by a manifestation of the same underlying construct. Similar to previous studies,18 our study calculated the Cronbach a per subscale and a score above 0.70 was considered to indicate sufficient homogeneity of the subscale’s items.18,19 Test-Retest Reliability. Test-retest reliability is defined as the extent to which scores of the same patients under the same conditions coincide on repeated measurements.17 The period between repeated measurements should be long enough to prevent recall of the tested items but short enough to ensure that no change in the clinical symptoms has occurred.19 In this study a period of 1 week after the initial examination was chosen to assess test-retest reliability. Intraclass correlation coefficients (ICCs) were calculated, and positive reliability was assumed when the ICC was at least 0.70 for all tested subscales.19 Construct Validity. Construct validity is defined as the degree to which the scores of a PRO instrument are consistent with the a priori hypothesis, based on the assumption that the PRO instrument validly measures the construct to be measured.17 Construct validity was assessed by correlating the subscales of the MKQ with the subscales of the KOOS. The KOOS, as an extension of the Western Ontario and McMaster Universities Osteoarthritis Index, was used because it presents a valid, reliable, and responsive selfadministered instrument that can be used for followup examinations of several types of knee injury.20,21 Pearson correlation coefficients (PCCs) were calculated. Similar to previous studies, positive construct validity was assumed when the PCC was at least 0.70 for all measured subscales.22 Responsiveness. Responsiveness is defined as the ability of a PRO instrument to detect changes over time of the construct to be measured.17 Responsiveness was evaluated 4 months after the initial presentation of patients in our outpatient clinic. To assess responsiveness, patients completed the MKQ and a global perceived effect (GPE) score consisting of only 1 question on the patients’ subjective opinion regarding improvement or worsening of their knee function during the past 4 months. The list of potential answers contained 7 categories (much better [þ3], better [þ2], somewhat better [þ1], no change

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[0], somewhat worse [1], worse [2], and much worse [3]) for each subscale of the MKQ. The period of 4 months was chosen to be long enough to allow for a clinical change and short enough to ensure that the patients were able to recall their health state during their initial presentation. Spearman correlation coefficients (SCCs) were calculated. According to other authors, an SCC between the change in the MKQ score and the GPE score of at least 0.40 was assumed to indicate high responsiveness.18 Correlations of Original and Calculated Scores. For the evaluation of the ability of the MKQ to calculate the scores evaluated by the original questionnaires (KOOS, IKDC score, Lysholm knee score, WOMET score, and Tegner score), the PCC was calculated, followed by a linear regression analysis. A positive correlation between the original and calculated scores was assumed when the PCC was at least 0.70. Statistical Analysis The results were compared by calculating the SCC and PCC with a linear regression analysis. P < .05 determined significance. Statistics were calculated using commercially available programs (SigmaStat 3.1 and SigmaPlot 8.02; Systat Software, Chicago, IL).

Table 1. Diagnoses of Study Collective (n ¼ 152)

ACL tear Knee pain State after high tibial osteotomy MCL tear Meniscal tear Lateral meniscus Medial meniscus PCL tear State after knee joint dislocation State after MPFL reconstruction Osteochondral lesion Tibial Femoral Retropatellar State after patellar dislocation Knee osteoarthritis Knee osteochondritis dissecans State after distal femoral fracture State after patellar fracture State after tibial plateau fracture Quadriceps tendon rupture Traumatic prepatellar bursitis State after knee arthroplasty Patellar pseudarthrosis Chronic prepatellar bursitis

Total (n ¼ 152) 21 9 4 4 7 3 9 4 3 2 5 1 3 1 3 15 1 7 12 27 8 1 10 1 2

Men (n ¼ 77) 7 5 3 2 5 3 5 1 2 0 4 1 3 0 1 5 0 3 6 17 5 1 4 0 2

Women (n ¼ 75) 14 4 1 2 2 0 4 3 1 2 1 0 0 1 2 10 1 4 6 10 3 0 6 1 0

ACL, anterior cruciate ligament; MCL, medial collateral ligament; MPFL, medial patellofemoral ligament; PCL, posterior cruciate ligament.

Results Patients and Study Design Validity, reliability, and responsiveness of the MKQ were determined in this prospective clinical study. Between August 2012 and July 2014, 152 consecutive patients (mean age, 47 years; SD, 18.0 years; minimum, 18 years; maximum, 87 years) of 176 patients completed the MKQ, KOOS, IKDC score, Lysholm knee score, WOMET score, and Tegner score at the initial presentation for the evaluation of validity. Table 1 shows the diagnoses of these patients, representing a wide spectrum of knee disorders. Completion of the MKQ took about 8 minutes (mean time, 7.8 minutes; SD, 2.2 minutes; minimum, 2.4 minutes; maximum, 14.7 minutes). All patients received a second MKQ at their initial visit to be completed at home after 1 week and send back to our institution to determine test-retest reliability. Figure 1 shows the clinical study profile. Approximately 4 months after the initial visit, responsiveness was assessed by sending the MKQ and the GPE score by mail to the patients to complete at home. Floor and Ceiling Effects The highest score achieved on the MKQ was 95 points, and the lowest was 18 points. As such, none of the patients achieved the highest or lowest score possible, and thus there were no floor or ceiling effects to be described.

Internal Consistency The Cronbach a was calculated for each subscale of the MKQ. Values of at least 0.80 showed a high consistency for all items in 1 subscale (Table 2). Test-Retest Reliability Retesting was performed a mean of 8 days (SD, 5.1 days; minimum, 3 days; maximum, 28 days) after the patients’ initial consultation in our outpatient clinic. Of the patients, 103 returned the completed questionnaire, 3 refused to take part in further testing, and 46 did not respond (Fig 1). ICCs were between 0.91 and 0.96 for all subscales of the MKQ (Table 2). Construct Validity Assessment of construct validity included a correlation of the subscales of the MKQ with the subscales of the KOOS. A PCC of at least 0.78 was calculated for all subscales (Table 3). Responsiveness One hundred patients returned the completed MKQ and GPE score 124 days (SD, 7.5 days; minimum, 104 days; maximum, 141 days) after the initial assessment. Three patients refused to take part in further data assessment, and 49 patients did not respond (Fig 1). Two patients rated their knee function state as worse or

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Fig 1. Clinical study profile and flowchart of study process.

much worse; 70 patients as somewhat worse, no change, or somewhat better; and 28 patients as better or much better. The SCC was 0.41 for symptoms, 0.54 for pain, 0.62 for work and ADL, 0.71 for SRA, and 0.49 for physical function and knee-related QOL. Correlations of Scores Figure 2 shows the results of the different knee questionnaires when we compared the original scores with the scores calculated from the MKQ. PCCs between the original scores and the calculated scores are shown in Table 4. The high degree of correlation (PCC between 0.80 and 0.91 [P < .05]) implies a great representation of all single scores in the MKQ.

Discussion The principal findings of this study showed that the MKQ is a valid, reliable, and responsive PRO questionnaire for assessing knee function. Correlation of the original KOOS, IKDC score, Lysholm knee score, WOMET score, and Tegner score with the calculated scores (from the MKQ) resulted in a high degree of correlation (P < .05). These findings indicate that the MKQ is able to reproduce 5 of the most commonly

applied knee outcome scores in the form of a single 33item questionnaire. Scientific Assessment of Outcomes by PRO Questionnaires In recent years the importance and use of PRO questionnaires in outcome studies as measurement tools in addition to the physician-based objective evaluation have increased, most likely because of their advantages regarding financial and logistic concerns,23 allowing a comprehensive evaluation of the clinical outcome. Furthermore, avoiding face-to-face contact with patients eliminates a certain observer bias in terms of the interviewer knowing the purpose of the study. However, PRO questionnaires offer other possible sources of bias in terms of non-responses and incomplete responses.4 In this study 3 patients refused to participate in the assessment of test-retest reliability and responsiveness. The non-responding rates of 32% in assessing test-retest reliability and 34% in assessing responsiveness, comparable with dropout rates of other validation studies in the current literature,18,24 could be minimized in further studies by reminding the participating patients by mail or telephone, as shown by Parker and Dewey.4

Table 2. Internal Consistency and Test-Retest Reliability (n ¼ 103) MKQ Symptoms Pain Work and ADL SRA Physical function and knee-related QOL

Test Mean (SD) 54.1 (16.3) 65.1 (19.8) 56.0 (20.2) 56.7 (17.6) 34.3 (20.2) 53.3 (17.9)

Retest Mean (SD) 54.0 (17.3) 65.5 (19.2) 56.0 (20.1) 55.8 (18.7) 38.4 (21.3) 53.8 (18.8)

Test-Retest Difference 0.1 0.4 0.2 0.9 4.0 0.5

ICC (95% CI) 0.95 (0.93-0.97) 0.94 (0.92-0.96) 0.96 (0.94-0.97) 0.91 (0.87-0.94) 0.96 (0.96-0.97) 0.95 (0.93-0.97)

Cronbach a 0.80 0.89 0.84 0.80 0.87

ADL, activities of daily life; CI, confidence interval; ICC, intraclass correlation coefficient; MKQ, Munich Knee Questionnaire; QOL, quality of life; SRA, sports and recreational activities.

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Table 3. Pearson Correlation Coefficients Determined When Comparing Subscales of MKQ With Subscales of KOOS (n ¼ 152) KOOS Subscale MKQ Subscale Symptoms Pain Work and ADL SRA Physical function and knee-related QOL

Symptoms r ¼ 0.78

Pain r ¼ 0.86

Activity

r ¼ 0.79

Sports

r ¼ 0.81

QOL

r ¼ 0.86

ADL, activities of daily life; KOOS, Knee Injury and Osteoarthritis Outcome Score; MKQ, Munich Knee Questionnaire; QOL, quality of life; SRA, sports and recreational activities.

Patients and Study Design Our study collective consisted of 152 consecutive patients with a mean age of 47 years and a male-female ratio of 1:1 and was comparable with other validation studies concerning the number of patients, age, and sex.18,25,26 In contrast to other validation studies focusing on specific knee disorders such as meniscal pathology11 or instability,14 the great number of different diagnoses of the presented patient collective represents the wide spectrum of knee disorders. Because, for the development of the MKQ, each single question was condensed from primary injuryespecific items, the MKQ is universally applicable to a rather broad spectrum of knee disorders, especially when

compared with other outcome studies using one of the other most commonly applied questionnaires.27,28 However, an additional number of patients, as well as more power, are needed to prove the efficacy of this outcome tool. Internal Consistency The Cronbach a of at least 0.80 resulting for all subscales indicates high internal consistency. Despite the integration of 1 item (stiffness) in the symptoms subscale, because this item did not fit in any of the other subscales, a high internal consistency could be reached for this subscale (Cronbach a ¼ 0.80). Nevertheless, other authors accepted a Cronbach a between 0.70 and

Fig 2. Box plots of results of different knee questionnaires when the original scores were compared with the scores calculated from the Munich Knee Questionnaire (MKQ) (n ¼ 152). For better comparability, the Tegner score (and calculated Tegner score [cTegner]) has been multiplied by 10. Data are given as vertical box plots (showing medians [horizontal box line]; 25% to 75% interquartile ranges; and standard deviations [horizontal line]). (cIKDC, calculated International Knee Documentation Committee score; cKOOS, calculated Knee Injury and Osteoarthritis Outcome Score; cLysholm, calculated Lysholm score; cWOMET, calculated Western Ontario Meniscal Evaluation Tool score; IKDC, International Knee Documentation Committee score; KOOS, Knee Injury and Osteoarthritis Outcome Score; WOMET, Western Ontario Meniscal Evaluation Tool score.)

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Table 4. Pearson Correlation Coefficients Determined When Comparing Original Scores and Calculated Scores (n ¼ 152) MKQ Calculated KOOS Calculated IKDC score Calculated Lysholm score Calculated WOMET score Calculated Tegner score

KOOS r ¼ 0.88

IKDC Score r ¼ 0.87

Lysholm Score

r ¼ 0.84

WOMET Score

r ¼ 0.91

Tegner Score

r ¼ 0.80

IKDC, International Knee Documentation Committee; KOOS, Knee Injury and Osteoarthritis Outcome Score; MKQ, Munich Knee Questionnaire; WOMET, Western Ontario Meniscal Evaluation Tool.

0.95 regarding internal consistency in previous studies.18,19 Briggs et al.29 even considered a Cronbach a greater than 0.60 as acceptable. Test-Retest Reliability Ours results showing ICCs between 0.91 and 0.96 for all subscales of the MKQ indicate great test-retest reliability, similar to other studies on outcome in the current literature.1,29,30 Despite the initial instructions to complete and return the second questionnaire after 7 days, a few patients returned it after only 3 days, increasing the risk of recall bias. Moreover, other patients returned it 28 days after their initial visit, increasing the possibility of a change in their clinical state. In the current literature an exact time point for the second assessment has not been established, but in most cases a period of 1 or 2 weeks is considered appropriate for determining test-retest reliability.19 Construct Validity Assessing construct validity of the MKQ was a challenge because no gold standard for comparison exists so far.31 The decision was made to correlate the subscales of the MKQ with the subscales of an already validated questionnaire. Such an approach is widely accepted and has been used by other authors. Thorborg et al.18 correlated their PRO questionnaire with the Short Form 36 items as a generic health status questionnaire, whereas Van Der Straeten et al.32 used KOOS, Western Ontario and McMaster Universities Osteoarthritis Index, and Short Form 12 items for comparison to prove construct validity. We chose the KOOSda wellestablished, valid, reliable, and responsive instrument that can be used for follow-up examination of several types of acute and chronic knee injuries, osteoarthritis, and cartilage lesions, as well as in patients after knee arthroplasty (comparable with our patient collective)d as our reference score. PCCs of at least 0.78 resulted for all subscales of the MKQ. Compared with other validation studies, these results indicate high construct validity of a self-reported questionnaire.30,33,34 Responsiveness The correlation between the GPE score and the change in scores on the first MKQ and third MKQ

showed a range from 0.49 to 0.71 for the pain, work and ADL, SRA, and physical function and knee-related QOL subscales, indicating high responsiveness. In contrast, the SCC of 0.41 for the symptoms subscale implies poorer responsiveness. Because the GPE score contains only a single question, subjective clinical changes in knee function may have been influenced considerably by persisting symptoms (e.g., stiffness of the knee joint) even though other symptoms changed considerably, thus possibly resulting in a supposed minor responsiveness, requiring a multi-item instrument.35 In the current literature various statistics to determine responsiveness are available; however, the method of choice remains unknown.36 Thorborg et al.18 showed the determination of effect size and standardized response mean in addition to the GPE score as a considerable amendment to assess responsiveness. Correlations of Scores Condensing items that measure the same construct into a single question is a common method to avoid redundancy of content.37 In a similar study previously published, a PRO shoulder questionnaire, the Munich Shoulder Questionnaire, was developed and validated, allowing for the assessment of 3 of the most commonly used outcome instruments in shoulder surgery (Constant score; Shoulder Pain and Disability Index; and Disabilities of the Arm, Shoulder and Hand score).38 This questionnaire is suitable for outcomes research in large collectives of patients with shoulder disorders and is currently in use at our outpatient clinic.39 High correlations between the original scores (KOOS, IKDC score, Lysholm knee score, WOMET score, and Tegner score) and the calculated scores led to the conclusion that the MKQ can be applied in further follow-up studies to compare different therapeutic approaches in patients with knee disorders. Because the items on the MKQ were developed as a combination of scores focusing on different knee disordersdfor example, the Lysholm score focusing on ligament injury or the WOMET score focusing on meniscal pathologydthe different aspects of knee function can be evaluated.

MUNICH KNEE QUESTIONNAIRE

Limitations To avoid financial and logistic burdens on the participating patients, the evaluations of test-retest reliability and responsiveness were conducted using questionnaires completed by patients at home. An influence of the change in setting cannot be excluded, but we consider it irrelevant regarding the test results because the initial assessment in our clinic, as well as the second and third assessments at home, were accomplished by self-administration. Furthermore, a time interval of 3 to 28 days seems not precise in the assessment of test-retest reliability. However, patients’ completion of the retest cannot be enforced within an exact interval of 7 days. Responsiveness was assessed by correlating a GPE score with the single subscales of the MKQ. Because the GPE score contained only a single question and the subscales of the MKQ contained between 5 and 9 questions, the GPE score could be less reliable than a multi-item instrument,35 resulting in reduced interpretability of responsiveness. Patient selection constitutes a further limitation that can be complicated by the presence of degenerative joint diseases. In addition, the heterogeneity of the patient collective regarding diagnosis may reduce the power of the questionnaire to address the specific injuries. Several authors prefer a heterogeneous patient collective combining different clinical entities to achieve a broad applicability of the measurement tool.40,41 However, this universal applicability of the MKQ may result in difficulties regarding the assessment of patients whose condition is deemed borderline, such as highly trained athletes or frail persons being in need of care. However, given that most patients can potentially be evaluated by this tool, these drawbacks might be negligible. Another limitation is that the MKQ has only been tested in Germany, and a cross-cultural adaptation into other languages and determination of the questionnaire’s clinimetric properties have to be conducted before the MKQ can be used worldwide.

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Conclusions The MKQ is a reliable and valid PRO questionnaire for assessing knee function. It seems to enable the calculation of the original items of the KOOS, IKDC score, Lysholm knee score, WOMET score, and Tegner score.

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