Greek cultural adaption and validation of the Kujala anterior knee pain scale in patients with patellofemoral pain syndrome

Translation, cross-cultural adaptation, and psychometric properties of the Persian version of the Pain Severity Scale in patients with patellofemoral pain

PURPOSE

To translate the Pain Severity Scale (PSS) into Persian (PSS-Persian) and study its psychometric properties in patients with patellofemoral pain (PFP).

MATERIALS AND METHODS

The psychometric properties of 112 patients with PFP were evaluated using a questionnaire. The structural validity, construct validity, reliability, internal consistency, and floor and ceiling effects were evaluated. Convergent validity was examined using Pearson's correlation coefficient between the PSS-Persian, Oxford Knee Score (OKS), Kujala Anterior Knee Pain Scale (AKPS), and Knee Outcome Survey Activities for Daily Living (KOS-ADL).

RESULTS

Good internal consistency was found (Cronbach's alpha = 0.889), and if the item was deleted varied from 0.868 to 0.886. The intraclass correlation coefficient (ICC) for test-retest reliability was 0.784. The factor loading for each item was >0.55. The PSS-Persian score showed a moderate correlation with the AKPS (r = -0.315, p = 0.001). The PSS-Persian score was also significantly correlated with the OKS (r = -0.231, p = 0.004) and KOS-ADL (r = -0.226, p = 0.017).

CONCLUSION

The data showed that the cultural adaptation process was successful. The PSS-Persian has acceptable measurement properties and is suitable for use in epidemiological, rehabilitation, and clinical contexts of patients with PFP in the Persian population.

Reliability and Validity Measures of the Patellofemoral Subscale KOOS-PF in Greek Patients with Patellofemoral Pain

Background: Patellofemoral pain (PFP) is one of the most common multifactorial musculoskeletal pathologies affecting the knee joint. The prevalence of PFP in the general population ranges from 11% to 17%, with higher rates observed in specific groups such as females, runners, military personnel, and young athletes. To assess symptoms associated with PFP, the patellofemoral subscale (KOOS-PF) was developed, consisting of 11 questions that evaluate pain, stiffness, and quality of life. The KOOS-PF scale has already been validated and shown to be reliable in both its Spanish and Arabic versions. Objectives: The aim of this study was to assess the reliability and validity of the KOOS-PF scale in the Greek language among the Greek population with patellofemoral pain. Methods: Fifty-five participants aged 18-65 years who suffered from PFP were evaluated in two phases on the first and third days to determine the reliability and validity of the measures of KOOS-PF in the Greek language. Construct validity was assessed using the knee outcome survey scale-activities of daily living scale (KOS-ADLS). Reliability was measured through repeated measurements (test-retest) using intraclass coefficient correlation (ICC), standard error of measurement (SEM), and smallest detectable difference (SDD). Internal consistency was evaluated using Cronbach's coefficient a. The significance level was set at 5% (α = 0.05). Results: The KOOS-PF measures showed high internal consistency reliability (Cronbach's alpha 0.87, p = 0.05) and high test-retest reliability (ICC = 0.95, p = 0.05, SEM = 3.7, SDC = 13.57). Additionally, the Greek version of the KOOS-PF exhibited high construct validity when correlated with the KOS-ADLS scale (r = 0.72, p = 0.001). Conclusions: The KOOS-PF scale displayed high reliability and construct validity for measuring patellofemoral pain in the Greek population.

Anatomic physeal-sparing MPFL reconstruction in skeletally immature patients shows favourable outcomes at a minimum of 24-month follow-up

Purpose

Recurrent patellar dislocation is a prevalent orthopaedic issue among active paediatric and adolescent populations. Bony surgical procedures are not recommended in growing patients; therefore, the focus of surgery is on restoring the medial patellar ligaments, with different reconstructive techniques available. This retrospective case series focuses on the 2-year outcomes of medial patellofemoral ligament (MPFL) reconstruction in skeletally immature patients with open physis.

Methods

Twenty-four consecutive patients with patellofemoral instability and open growth plates underwent anatomic MPFL reconstruction with a physeal-sparing technique. All subjects have had more than three episodes of true patellar dislocations. Preoperative radiographic examination included anteroposterior and lateral views to assess patella alta and limb alignment. Magnetic resonance imaging was performed to evaluate trochlear dysplasia and tibial tubercle-trochlear groove (TT-TG) distance. The patients were questioned regarding complications and clinical outcomes using the visual analogue scale (VAS), Kujala and Paediatric International Knee Documentation Committee (Pedi-IKDC) score. Variables were evaluated using paired t test with significance at p < 0.05.

Results

The mean age at the time of operation was 13.04 years (9-16 years). The cohort was followed for a mean duration of 38.66 months (24-86 months). The mean time from injury to surgery was 50.45 days (16-80 days). No growth arrest, limb-length discrepancies or angular deformities were observed post-operatively during the whole follow-up period. No patellar re-dislocations were recorded throughout the study period. The VAS score improved significantly from 5.67 (4-8) to 1.88 (0-4) (p < 0.01). The Kujala score improved significantly from 64.67 (44-81) preoperatively to 87.58 (77-100) post-operatively (p < 0.01). The Pedi-IKDC also increased significantly from 58.81 (34.80-77.70) preoperatively to 90.64 (70.70-100) post-operatively (p < 0.01). The vast majority of patients (87.5%) returned to their pre-injury activity level. Boys scored better than girls in VAS, Pedi-IKDC and Kujala score post-operatively, but these differences were not statistically significant.

Conclusion

Physeal-sparing MPFL reconstruction in children and adolescents yields excellent midterm results and allows patients to return to sports without redislocation of the patella. Boys scored better than girls in VAS, Pedi-IKDC and Kujala score post-operatively, but these differences were not statistically significant.

Level of Evidence

IV: case series with no comparative group.

Anterior Knee Pain Scale (AKPS): structural and criterion validity in Brazilian population with patellofemoral pain

PURPOSE

To identify the best internal structure of the Brazilian version of the Anterior Knee Pain Scale (AKPS), comparing different instrument structures (structural validity) and correlating the scores of the versions (criterion validity).

METHODS

We included Brazilian volunteers, aged ≥ 18 years, with patellofemoral pain (PFP) for at least 3 months. We used the confirmatory factor analysis and considered the following fit indices: chi-square/degrees of freedom (DF), comparative fit index (CFI), Tucker-Lewis index (TLI), root mean square error of approximation (RMSEA). We considered the structure with the lowest values of the Akaike information criterion (AIC), sample size adjusted Bayesian information criterion (SABIC), and assessed criterion validity using Pearson correlation coefficient (r) to correlate the long and short versions.

RESULTS

The study included 101 participants, mostly women (65.3%), young adults (~ 31 years old), overweight (BMI > 25 kg/m2), incomplete higher education (37.6%), and physically active (64.4%). The original 1-domain, 13-item structure showed adequate fit indices (chi-square/GL < 3.00, TLI and CFI > 0.90, and RMSEA < 0, 08). However, items 11 and 12 had a factorial load of less than 0.23. Therefore, we excluded items 11 and 12 and found adequate fit indices (chi-square/GL < 3.00, TLI and CFI > 0.90, and RMSEA < 0, 08) and lower AIC and SABIC values. We observed a correlation coefficient above the acceptable cutoff of 0.70 (r = 0.966, p-value < 0.001) between the versions.

CONCLUSION

The 11-item AKPS (without items 11 and 12) is the version with the most adequate internal structure and correlates satisfactorily with the long version of the instrument.

Patient-Reported Outcome Measures for Adults and Adolescents With Patellofemoral Pain: A Systematic Review of Construct Validity, Reliability, Responsiveness, and Interpretability Using the COSMIN Methodology

OBJECTIVE: We aimed to appraise the construct validity, reliability, responsiveness, and interpretability of patient-reported outcome measures (PROMs) used to assess function and pain in adults and adolescents with patellofemoral pain (PFP). DESIGN: Systematic review of measurement properties LITERATURE SEARCH: We searched the PubMed, CINAHL, Scopus, SPORTDiscus, and Cochrane Library databases from inception to January 6, 2022. STUDY SELECTION CRITERIA: We included studies that assessed the measurement properties of English-language PROMs for PFP and their cultural adaptations and translations. DATA SYNTHESIS: Using the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) methodology, we determined overall ratings and quality of evidence for construct validity, internal consistency, reliability, measurement error, and responsiveness. We extracted data related to interpretability for clinical use. RESULTS: After screening 7066 titles, 61 studies for 33 PROMs were included. Only 2 PROMs had evidence of "sufficient" or "indeterminate" quality for all measurement properties. The Knee injury and Osteoarthritis Outcome Score patellofemoral subscale (KOOS-PF) had "low" to "high" quality evidence for a rating of "sufficient" for 4 measurement properties. The Lower Extremity Functional Scale (LEFS) had very low-quality evidence for a "sufficient" rating for 4 measurement properties. The KOOS-PF and LEFS were rated "indeterminate" for structural validity and internal consistency. The KOOS-PF had the best interpretability with reported minimal important change and 0% ceiling and floor effects. No studies examined cross-cultural validity. CONCLUSION: The KOOS-PF and LEFS had the strongest measurement properties among PROMs used for PFP. More research is needed, particularly regarding structural validity and interpretability of PROMs. J Orthop Sports Phys Ther 2023;53(8):1-20. Epub: 20 June 2023. doi:10.2519/jospt.2023.11730.

Patient-reported outcome measures for patellofemoral disorders: a systematic review

INTRODUCTION

Patellofemoral conditions include, but are not limited to, anterior knee pain syndrome and patellar instability. Patients and surgeons may find it difficult to identify the specific source of the symptoms and clinical scenarios, so patient-reported outcome measures (PROMs) may be a useful diagnostic aid. There are a number of available PROMs for patellofemoral conditions, which are often used indistinctly. This systematic review explores the available PROMs for patellofemoral conditions, their use and methodological quality.

METHODS

A systematic review was conducted, searching for scientific articles relating to PROMs in patellofemoral conditions, from inception to July 2022. Scoring systems including physician-directed or imagining assessment were not included. All types of conditions in the patellofemoral joint were considered.

RESULTS

Twenty-two relevant PROMs were encountered, divided into four categories: eight PROMs for anterior knee pain syndrome, five for patellar instability, four for other patellofemoral conditions and five for non-specific PROMs.

CONCLUSIONS

While many PROMs have been found used in patellofemoral research, only few of them have showed sufficient methodological quality. In addition, PROMs employed in PF literature are often inaccurately chosen. This review may help authors to better understand the characteristics of specific patellofemoral PROMs, in order to select the more appropriate and recommended ones.

LEVEL OF EVIDENCE

Level II.

Cross-Culturally Adapted Versions of Patient Reported Outcome Measures for the Lower Extremity

Background

A large number of patient reported outcome measures (PROMs) have been developed in the English language for various lower extremity orthopaedic pathologies. Twenty different PROMs were recommended for 15 specific musculoskeletal lower extremity pathologies or surgeries. However, the availability of cross-culturally adapted versions of these recommended PROMs is unknown.

Purpose

The purpose of this study was to identify the cross-culturally adapted versions of recommended PROMs for individuals experiencing orthopedic lower extremity pathologies or undergoing surgeries, and to identify the psychometric evidence that supports their utilization.

Study design

Literature Review.

Methods

PubMed, Embase, Medline, Cochrane, CINAHL, SPORTDisucs and Scopus were searched for cross-culturally adapted translated studies through May 2022. The search strategy included the names of the 20 recommended PROMs from previous umbrella review along with the following terms: reliability, validity, responsiveness, psychometric properties and cross-cultural adaptation. Studies that presented a non-English language version of the PROM with evidence in at least one psychometric property to support its use were included. Two authors independently evaluated the studies for inclusion and independently extracted data.

Results

Nineteen PROMS had cross-culturally adapted and translated language versions. The KOOS, WOMAC, ACL-RSL, FAAM, ATRS, HOOS, OHS, MOXFQ and OKS were available in over 10 different language versions. Turkish, Dutch, German, Chinese and French were the most common languages, with each language having more than 10 PROMs with psychometric properties supporting their use. The WOMAC and KOOS were both available in 10 languages and had all three psychometric properties of reliability, validity, and responsiveness supporting their use.

Conclusion

Nineteen of the 20 recommended instruments were available in multiple languages. The PROM most frequently cross-culturally adapted and translated were the KOOS and WOMAC. PROMs were most frequently cross-culturally adapted and translated into Turkish. International researchers and clinicians may use this information to more consistently implement PROMs with the most appropriate psychometric evidence available to support their use.

Level of evidence

3a.

Patient-Reported Outcome Measures for Adults and Adolescents with Patellofemoral Pain: A Systematic Review of Content Validity and Feasibility Using the COSMIN Methodology

OBJECTIVE: To assess the content validity and feasibility of patient-reported outcome measures (PROMs) used to assess pain and function in adults and adolescents with patellofemoral pain (PFP). DESIGN: Systematic review. LITERATURE SEARCH: We searched the databases PubMed, CINAHL, Scopus, SPORTDiscus, and the Cochrane Library from inception to January 6, 2022. STUDY SELECTION CRITERIA: We included studies that described the development or evaluation of the content validity of English-language PROMs for PFP, as well as their translations and cultural adaptations to different languages. DATA SYNTHESIS: Using the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) methodology, we determined overall ratings and quality of evidence for the relevance, comprehensiveness, and comprehensibility of PROMs. We extracted data related to feasibility for clinical use (eg, administration time and scoring ease). RESULTS: Forty-three studies for 33 PROMs were included. The overall quality of most studies was "inadequate" due to failure to engage stakeholders and/or ensure adherence to rigorous qualitative research procedures. Of all PROMs evaluated, the Knee injury and Osteoarthritis Outcome Score-Patellofemoral subscale (KOOS-PF), was the only PROM with sufficient content validity components. Quality of evidence for content validity of the KOOS-PF was low. Most PROMs were rated feasible for clinical and research purposes. CONCLUSION: Most PROMs used to measure pain and function in patients with PFP have inadequate content validity. The KOOS-PF had the highest overall content validity. We recommend the KOOS-PF for evaluating pain and function (in research and clinical practice) in adults and adolescents with PFP. J Orthop Sports Phys Ther 2023;53(1):23-39. Epub: 18 October 2022. doi:10.2519/jospt.2022.11317.

Comparing hip and knee focused exercises versus hip and knee focused exercises with the use of blood flow restriction training in adults with patellofemoral pain

BACKGROUND

Hip and knee strengthening exercises are implemented in rehabilitation of patellofemoral pain patients, but typically use high loads (70% of 1 repetition maximum). This may lead to increased patellofemoral joint stress. Low load training (20-30% of 1 repetition maximum) with blood flow restriction could allow for exercise strength benefits to proximal and distal muscles with reduced joint stress and by promoting hypoalgesia.

AIM

The aim of this study was to compare hip and knee focused exercises with and without blood flow restriction in adults with patellofemoral pain for short term effectiveness.

DESIGN

A randomized observed-blind controlled trial.

SETTING

Musculoskeletal laboratories of the European University Cyprus, Nicosia, Cyprus.

POPULATION

60 volunteer patients, 18-40 years of age with patellofemoral pain.

METHODS

Participants were randomly assigned to (1 reference group) hip and knee strengthening at (70% of 1 repetition maximum) or (2 experimental group) Strengthening with blood flow restriction at (30% of 1 repetition maximum at 70% of limb occlution pressure). Treatments took place 3 times per week for 4weeks and outcomes were assessed at baseline, end of treatment and at 2-month follow-up. The primary outcome was the Kujala Anterior Knee Pain Scale and secondary outcomes were worst and usual pain, pain with Single leg Squats, the maximum pain free flexion angle, the Tampa Scale of kinesiophobia, the Pain Catastrophizing Scale and isometric strength of knee extensors, hip extensors and hip abductors.

RESULTS

No difference were found for the main outcome of this study between groups. There was a significant effect of time for all outcome measures in both groups. Between group differences showed a significant difference for isometric strength of Knee extensor values at 2 month follow-up F(1,58)=5.56, P=0.02, partial η2=0.09, 459.4 (412.13, 506.64) vs. 380.68 (333.42, 427.93) and in worst pain post-treatment F(1,58)=5.27, P=0.02, partial η2=0.08, 0.76 (0.48, 1.04) vs. reference group 1.30 (0.91, 1.68) with significantly better scores in the blood flow restriction group.

CONCLUSIONS

Blood flow restriction exercises of the hip and knee musculature used in this study were as effective as usual exercises of Hip and knee musculature in reducing symptoms in the short term. They also indicated greater increases in strength and reduction of worst pain post-treatment.

CLINICAL REHABILITATION IMPACT

Further research is needed to investigate the dose response relationship with longer follow-ups.

Patient-Reported Outcome Measures (PROMs) Relevant to Musculoskeletal Conditions Translated and Validated in the Greek Language: A COSMIN-Based Systematic Review of Measurement Properties

BACKGROUND

The use of patient-reported outcome measures (PROMs) constitutes a valuable tool in evaluating the quality of care offered in orthopaedic surgery. The aim of this review is to identify the PROMs that have been translated into and validated in the Greek language, summarise their measurement properties, and evaluate their methodological quality according to the COSMIN Risk of Bias Checklist.

METHODS

A structured literature search was conducted using the databases PubMED/MEDLINE, Embase, Scopus, and the Cochrane Library in order to identify PROMs relevant to musculoskeletal conditions translated and validated in the Greek language. The methodological quality of the studies was assessed according to the COSMIN Risk of Bias Checklist, and the quality of measurement properties according to the COMSIN criteria.

RESULTS

Literature search yielded 6743 articles. After removal of duplicates and screening of the articles, 32 studies including PROMs related to musculoskeletal conditions were identified. The studies included 31 PROMs and reported 171 measurement properties. Methodological quality was adequate for 81 of them (47.3%). The most commonly reported measurement properties were internal consistency, reliability, construct validity and responsiveness.

CONCLUSION

The majority of PROMs translated into Greek involves the lower extremity and especially knee pathologies. The search revealed that there are areas of Musculoskeletal Medicine such as skeletal trauma, musculoskeletal oncology, and paediatric orthopaedics in which patient reported-outcome measures have not been translated into Greek. Translation and validation of new outcome measures is encouraged, using studies designed in compliance with the COSMIN guidelines, and further validation of the translated instruments.

The reliability, validity, interpretability, and responsiveness of the Norwegian version of the Anterior Knee Pain Scale in patellofemoral pain

PURPOSE

To determine the reliability, validity, responsiveness, and interpretability of the Norwegian Anterior Knee Pain Scale (AKPS) in patients with patellofemoral pain (PFP).

METHODS

The AKPS was translated into Norwegian. One hundred and twelve patients with PFP participated in a randomized controlled trial. Fifty stable patients completed the AKPS at a one-week interval for test-retest reliability. Smallest detectable change (SDC) and floor/ceiling effects were evaluated. Validity and responsiveness were assessed using hypothesis testing for correlations with other scores and known-group validity. Minimal important change (MIC) and responsiveness were evaluated at three months.

RESULTS

Intraclass correlation coefficient (ICC_agreement) for sum score was 0.83. Smallest detectable change was 13. No floor/ceiling effects were found for total score, but ceiling effects were found on eight of 13 individual items. Hypothesis testing for construct validity and responsiveness was largely confirmed but correlations were moderate to low. The MIC was 11. Area under receiver operating characteristic curve was 0.66 (95% CI 0.56-0.77) indicating moderate responsiveness.

CONCLUSIONS

The Norwegian AKPS had comparable measurement properties to other versions, with acceptable reliability and construct validity. We found moderate responsiveness which may be related to ceiling effects on several items.Implications for rehabilitationThe Anterior Knee Pain Scale (AKPS) is a commonly used outcome measure in patellofemoral pain, having acceptable reliability and moderate responsiveness.A change in AKPS total score of 11 points would be considered important by the patient, although changes up to 13 points may be due to measurement error.The AKPS has limitations including ceiling effects on most individual items in this patient population, and low correlation between pain and AKPS that questions the validity of the score. A revision of the score should be considered.

Patellofemoral Pain

Patellofemoral pain (PFP) is a common musculoskeletal-related condition that is characterized by insidious onset of poorly defined pain, localized to the anterior retropatellar and/or peripatellar region of the knee. The onset of symptoms can be slow or acutely develop with a worsening of pain accompanying lower-limb loading activities (eg, squatting, prolonged sitting, ascending/descending stairs, jumping, or running). Symptoms can restrict participation in physical activity, sports, and work, as well as recur and persist for years. This clinical practice guideline will allow physical therapists and other rehabilitation specialists to stay up to date with evolving PFP knowledge and practices, and help them to make evidence-based treatment decisions. J Orthop Sports Phys Ther. 2019;49(9):CPG1-CPG95. doi:10.2519/jospt.2019.0302.

Patient-Reported Outcome Measures for Patellofemoral Instability: a Critical Review

PURPOSE OF REVIEW

The purpose of this paper was to review the current psychometric properties of patient-reported outcome measures that are commonly used for patients with patellofemoral instability. This review provides evidence to guide the selection of subjective outcome measures for assessing outcomes in clinical care and research studies.

RECENT FINDINGS

At the present time, there are two patient-reported outcome measures that have been designed for, and tested on, large cohorts of patellofemoral instability patients, the Banff Patella Instability Instrument (BPII) and the Norwich Patellar Instability Score (NPI). The BPII is a wholistic quality of life outcome measure and the NPI is a symptom score. The use of disease-specific outcome measures such as the BPII and NPI, in combination with generic knee, functional activity, and/or psychological outcome measures that have been proven to be valid and reliable for the patellofemoral instability population, is most likely to provide a well-rounded evaluation of treatment outcomes.

Validation of the Arabic version of the Kujala patellofemoral pain scoring system

BACKGROUND

Patellofemoral knee pain is a common cause of anterior knee pain. The Kujala anterior knee pain score is a scoring system for the clinical assessment of disease severity. The purpose of this cross-sectional study was to validate an Arabic translation of the original Kujala anterior knee pain score to assess Arabic-speaking patients with patellofemoral pain syndrome.

METHODS

The Kujala anterior knee pain score was translated into Arabic by a group of native Arabic and native English speakers including orthopedic surgeons, residents, and a medical student. Questionnaires were filled by 127 patients visiting our outpatient department complaining of anterior knee pain diagnosed clinically and after exclusion of other pathologies. Questionnaires were re-filled at least 2 weeks later via phone contact from a member of our team. After exclusions, 97 questionnaires were analyzed for reliability using Cronbach's alpha for the scoring system's internal consistency and intraclass correlation coefficient for test-retest analysis.

RESULTS

The mean score of the questionnaire before the follow-up was 62.38 (±17.78) and 64.02 (±18.47) after the follow-up. The scoring system's internal consistency measured via Cronbach's alpha was 0.824. Average ICC for the scoring system was 0.948 (CI: 0.923-0.965) and for single measures, 0.902 (CI: 0.856-0.933). Further, 94.8% of patients were contacted before initiating physiotherapy. Forty-six of the patients (47.4%) showed improvement in their scores when contacted, 44 patients (45.4%) showed a slight worsening of their scores and seven patients' (7.2%) scores were unchanged.

CONCLUSIONS

The Arabic translation of the Kujala anterior knee pain score is a valid, reliable, useful, and easy-to-interpret scoring system to assess Arabic-speaking patients with patellofemoral pain syndrome.

Validation of the German version of the Kujala score in patients with patellofemoral instability: a prospective multi-centre study

INTRODUCTION

The Kujala score is the most frequently used questionnaire for patellofemoral disorders like pain, instability or osteoarthritis. Unfortunately, we are not aware of a validated German version of the Kujala score. The aim of our study was the translation and linguistic validation of the Kujala score in German-speaking patients with patella instability and the assessment of its measurement characteristics.

MATERIALS AND METHODS

The German Kujala score was developed in several steps of translation. In addition to healthy controls, the Kujala German was assessed in consecutive patients undergoing reconstruction of the medial patellofemoral ligament for recurrent patellar dislocations. Pre-op, 6 and 12 months postop the patients completed the Kujala German score, the KOOS, the Lysholm score, a VAS Pain, and the SF-12v2 scores. In addition, there was a Kujala German Score retest preop after a 1-week interval.

RESULTS

We found high reliability in terms of internal consistency for the Kujala score (Cronbach's alpha = 0.87). Convergent validity with the KOOS (symptom r = 0.65, pain r = 0.78, ADL r = 0.74, sports/recreation r = 0.84, quality of life r = 0.70), the Lysholm score (r = 0.88) and the SF-12 physical component summary score (r = 0.79) and VAS pain (r = - 0.71) was also very high. Discriminant validity in terms of correlation with the SF-12 mental component summary Score was satisfactory (r = 0.14).

CONCLUSIONS

In conclusion, the German version of the Kujala score proved to be a reliable and valid instrument in the setting of a typical patellofemoral disease treated with a standard patellofemoral procedure.