# Adaptation and Validation of the Malay Version of the Osteoarthritis Knee and Hip Quality of Life Questionnaire among Knee Osteoarthritis Patients

Authors: Azidah Abdul Kadir; Mohd Faizal Mohd Arif; Azlina Ishak; Intan Idiana Hassan; Norhayati Mohd Noor
Journal: BioMed Research International
 (2018)

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## Abstract

Objective. To adapt and validate the Malay version of Osteoarthritis Knee and Hip Quality of Life (OAKHQOL) questionnaire.Design. The OAKHQOL was adapted into Malay version using forward-backward translation methodology. It was then validated in a cross-sectional study of 191 patients with knee osteoarthritis (OA). Patients completed the OAKHQOL and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire. Confirmatory analysis, reliability analysis, and Pearson correlation test were performed.Results. The new five-factor model of 28 items demonstrated an acceptable level of goodness of fit (comparative fit index = 0.915, Tucker-Lewis index = 0.905, incremental fit index = 0.916, chi-squared/degree of freedom = 1.953, and root mean square error of approximation = 0.071), signifying a fit model. The Cronbach’s alpha value and the composite reliability of each construct ranged from 0.865 to 0.933 and 0.819 to 0.921, respectively. The Pearson correlation coefficient between the OAKHQOL and the WOMAC showed adequate criterion validity. Known groups validity showed statistical difference in body mass index in physical activity, mental health, and pain construct. The pain domain was statistically different between the age groups.Conclusion. The Malay version OAKHQOL questionnaire is a valid and reliable instrument to assess health-related quality of life in knee OA patients.


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## Body

## 1. Introduction

Osteoarthritis (OA) is the most common disease of joints in adults around the world [1, 2]. Due to its chronicity in nature, it is the major cause of pain and disability. OA may affect not only physical functioning, but also mental health (anxiety and depression), sleep, work ability, interpersonal interactions, self-esteem, quality of life, sexuality, and participation [3, 4].There are few validated instruments used in studies to assess health-related QOL in patients with OA specifically. The Medical Outcomes Study Short-Form 36 (SF36), which has been widely applied to assess QOL, is not disease-specific to OA and was found to have low response rate in population more than 65 years of age [5]. The Lequesne index and Western Ontario and McMaster Universities Osteoarthritis (WOMAC) questionnaire, which are more disease-specific, are able to measure only pain and function but not the other domains of QOL such as mental, social, and sexual domains [6, 7]. It was suggested that the SF-36 and WOMAC should be used in combination [8]; however, they may still fail to capture specific QOL aspects related to hip or knee osteoarthritis. Knee Injury and Osteoarthritis Outcome Score (KOOS) is another questionnaire but its assessment is not limited to quality of life because it includes pain, other symptoms, activity of daily living, sports, and recreational activity measurements [9]. Thus, the Osteoarthritis Knee and Hip Quality of Life (OAKHQOL) scale questionnaire was developed and validated to measure the impact of specifically knee and hip osteoarthritis on the patient’s QOL.The OAKHQOL is a specific tool to measure QOL in knee and hip OA as it takes into account specific themes that are exclusive to the QOL of patients with knee and hip OA (social support, sleep, side effects of drugs, plans for the future, embarrassment to be seen by people, use of public transport, difficulty in moving after staying in the same position, and sexuality) [10]. It has 43 items which fall into five domains: physical activity, pain, mental health, social functioning, and social support. Evaluation of the OAKHQOL has shown the reliability of the five domains to be satisfactory (interclass correlation coefficients: 0.70–0.85), the construct validity to be adequate (Spearman correlation coefficients: 0.43–0.75), and the discrimination to be satisfactory [10].Confirmatory factor analysis (CFA) is a theory-testing model as opposed to exploratory factor analysis (EFA) which is a theory-generating method [11]. CFA is a type of structural equation modeling (SEM) that specifically deals with measurement models, that is, the relationships between observed measures or indicators and latent variables or factors [12, 13]. It is powerful because it provides explicit hypothesis testing for factor analytic problems.Assessing the QOL among knee OA patients is important to ensure holistic care for the patient. Despite this, the reliability and validity of the OAKHQOL in the Malaysian context have not been established. The need for a validated questionnaire suitable to the local population based on the language is very important as it is more accurate to illustrate the real impact of the disease on the patient’s QOL. Hence, this study aimed to determine the psychometric properties of the Malay version of the OAKHQOL among knee OA patients.


## 2. Materials and Methods

A cross-sectional study was conducted among 191 patients diagnosed with knee OA between February and August 2014 at the Outpatient Clinic, Universiti Sains Malaysia Hospital, a tertiary teaching hospital in Malaysia. A total of 210 patients were invited, and only 191 patients fulfilled the inclusion and exclusion criteria and were recruited in the study, which give the response rate of 90%. Patients with unilateral or bilateral knee osteoarthritis diagnosed according to the clinical and radiological criteria of the American College of Rheumatology (knee pain and radiographic osteophytes plus at least one of three symptoms/signs), aged more than 50 years, who experienced morning stiffness of less than 30 minutes and crepitus on active motion, and who were able to read in the Malay language were included.Convenience sampling was applied, and written informed consent was taken. Patients were asked to fill out the Malay version OAKHQOL (Table7) and the validated Malay Version WOMAC. Sociodemographic data (age, gender, education, and race) and knee OA history were taken. Body mass index (BMI) measurements and weight-bearing anterior-posterior view X-rays of both knees were taken. The participants took about 15 minutes to complete both questionnaires. They also did not have to pay for their participation in the study.Sample size was determined based on Hair et al. (2010). The minimum sample size required for five or less constructs was 100 samples [14].


### 2.1. OAKHQOL Questionnaire

This questionnaire was developed by Rat et al. to assess quality of life in knee and hip OA patients [10, 15], specifically to assess health-related quality of life (HRQOL) [10]. The concept of this questionnaire was based on the World Health Organization (WHO) definition of QOL. This is a self-administered questionnaire. The original questionnaire was developed in French and later in English [15]. It was shown to capture patients’ perceptions of their disease, and it possesses the necessary psychometric properties of validity and reliability for use in clinical trials and observational studies [10, 15].In the original validation study, four factors were identified in the exploratory factor analysis based on scree plot and Eigen values. These factors were physical activities (19 items), mental health (14 items), social support (four items), and social functioning (three items). The pain factor (four items) was found to have loaded on the physical and mental health factors. However, based on expert opinions, the pain factor was included as an individual dimension. Therefore, the final English version of OAKHQOL consists of 43 items divided into five dimensions: physical activity, mental health, pain, social support, and social functioning as well as three additional items [10]. The three additional items are relationship, sexual activity, and professional life. The five dimensions (40 items) (Table 8) and three additional items are intended to be used separately. The three additional items are independent items and were not included in the analysis. Each item in the five dimensions is measured on a numerical rating scale from 0 to 10. The final scores were the mean of scores of all the items in respective domains that ranged between 0 to 10 [10].


### 2.2. Adaptation of the OAKHQOL Questionnaire

Forward and backward translation was carried out by a group of panelists consisting of family medicine specialists, physicians, linguists, and bilingual laymen. Modifications were made, and content validity was checked. The revised version was tested on 20 patients for face validity. These patients were excluded from the psychometric analysis.


### 2.3. WOMAC

WOMAC is a disease-specific, self-administered health status measure that is widely used to assess the symptoms and physical disability for people with hip and/or knee OA [16, 17]. It is widely used in OA research especially to evaluate clinical outcome measures as a result of treatment intervention [18]. The WOMAC measures total pain score, total stiffness score, and total physical functioning score. The original index consists of 24 questions (five questions for pain, two questions for stiffness, and 17 questions for physical function). It has been validated in Bahasa, Malaysia [16]. This questionnaire is available in a Likert version rated on an ordinal scale of 0 to 4 and also as a visual analog scale (VAS) [16]. In this study, a VAS version was used.


### 2.4. Statistical Analysis

Confirmatory factor analysis (CFA), reliability analysis, and Pearson correlation test were performed to assess the psychometric properties using SPSS version 22.0 and Analysis of Moment Structure (AMOS) software version 21.0. On preliminary data screening, cases with incomplete response were removed from data. Further assessment of normality and outliers was performed on the factor scores based on the critical ratio (i.e., for skewness and kurtosis to their standard error) and the Mahalanobis distance. Mahalanobis distance was used to identify the outliers by using AMOS software. It computes and tabulates the distance of every data from the center of all data distribution [19].The CFA was performed to examine the goodness of fit indices of the Malay OAKHQOL latent construct. Construct validity examines the degree to which a scale measures what it intends to measure [20]. Construct validity is achieved if the goodness of fit indices signify a model fit [20].The measurement of the model fit was checked with several goodness of fit indicators: comparative fit index (CFI), Tucker-Lewis index (TLI), incremental fit index (IFI), chi-squared/degree of freedom, and root mean square error of approximation (RMSEA) [12, 13, 21]. For approximate fit index, a value of more than 0.9 was taken for CFI, IFI, and TLI [21, 22]. Chi-squared/degree of freedom of less than 3 and RMSEA value of less than 0.08 were taken as indicators of an acceptable level [12, 13, 19].In addition to the overall evaluation of goodness of fit, the standardized factor loading (standardized regression weight) modification indices (MI) and squared multiple correlation (R2) were used as indicators to select which items should be removed in the model [12, 13]. MI suggested correlations between variables. A high MI value indicates redundancy in a pair of variables [12, 13]. Discriminant validity is also assessed by obtaining correlation values between the constructs. A correlation of more than 0.85 between constructs is considered to indicate poor discriminant validity [12, 13].Reliability analysis was measured using Cronbach’s alpha coefficient, composite reliability (CR), and average variance extracted (AVE). Reliability refers to the accuracy and precision of the measurement procedure. Cronbach’s alpha coefficient was measured using SPSS. Both CR and AVE were derived from CFA analysis and manually calculated based on published formula [19, 23]. A Cronbach’s alpha coefficient value of more than 0.7 and a CR equal to or greater than 0.6 represent a measure of satisfactory internal consistency [19, 24, 25]. AVE is the average percentage of variation explained by the variables in the construct or domain. The acceptable value for it was taken as more than 0.5 [19]. In this study, the test-retest reliability was not done due to time constraint and limited budget.The Pearson correlation test was performed to assess the criterion validity of the OAKHQOL. The test was done between the pain construct of the OAKHQOL and the pain construct of the WOMAC, as well as between the physical construct of the OAKHQOL and the functional construct of the WOMAC. The correlation coefficient of more than 0.5 but less than 0.8 was considered to be a good correlation [26].Known group validity is a method to support construct validity of a questionnaire. The method will evaluate the questionnaire ability to discriminate between the two groups known to differ on the variable of interest [27]. In this study, known group validity was assessed through gender, BMI, age groups of the patients, and Kellgren–Lawrence grading of the knee radiograph. We hypothesized that females, those aged more than 60 years [28], those having a BMI greater than 25 kg/m2, and those with more severe radiographic grading would have significant differences [10]. An independent t-test was used to analyze for gender, BMI, and age groups of the patients. One-way ANOVA test was used to analyze radiographic grading based on Kellgren–Lawrence classification. In the analysis for known group validity, the score for each domain was normalized to 0–100.


## 2.1. OAKHQOL Questionnaire

This questionnaire was developed by Rat et al. to assess quality of life in knee and hip OA patients [10, 15], specifically to assess health-related quality of life (HRQOL) [10]. The concept of this questionnaire was based on the World Health Organization (WHO) definition of QOL. This is a self-administered questionnaire. The original questionnaire was developed in French and later in English [15]. It was shown to capture patients’ perceptions of their disease, and it possesses the necessary psychometric properties of validity and reliability for use in clinical trials and observational studies [10, 15].In the original validation study, four factors were identified in the exploratory factor analysis based on scree plot and Eigen values. These factors were physical activities (19 items), mental health (14 items), social support (four items), and social functioning (three items). The pain factor (four items) was found to have loaded on the physical and mental health factors. However, based on expert opinions, the pain factor was included as an individual dimension. Therefore, the final English version of OAKHQOL consists of 43 items divided into five dimensions: physical activity, mental health, pain, social support, and social functioning as well as three additional items [10]. The three additional items are relationship, sexual activity, and professional life. The five dimensions (40 items) (Table 8) and three additional items are intended to be used separately. The three additional items are independent items and were not included in the analysis. Each item in the five dimensions is measured on a numerical rating scale from 0 to 10. The final scores were the mean of scores of all the items in respective domains that ranged between 0 to 10 [10].


## 2.2. Adaptation of the OAKHQOL Questionnaire

Forward and backward translation was carried out by a group of panelists consisting of family medicine specialists, physicians, linguists, and bilingual laymen. Modifications were made, and content validity was checked. The revised version was tested on 20 patients for face validity. These patients were excluded from the psychometric analysis.


## 2.3. WOMAC

WOMAC is a disease-specific, self-administered health status measure that is widely used to assess the symptoms and physical disability for people with hip and/or knee OA [16, 17]. It is widely used in OA research especially to evaluate clinical outcome measures as a result of treatment intervention [18]. The WOMAC measures total pain score, total stiffness score, and total physical functioning score. The original index consists of 24 questions (five questions for pain, two questions for stiffness, and 17 questions for physical function). It has been validated in Bahasa, Malaysia [16]. This questionnaire is available in a Likert version rated on an ordinal scale of 0 to 4 and also as a visual analog scale (VAS) [16]. In this study, a VAS version was used.


## 2.4. Statistical Analysis

Confirmatory factor analysis (CFA), reliability analysis, and Pearson correlation test were performed to assess the psychometric properties using SPSS version 22.0 and Analysis of Moment Structure (AMOS) software version 21.0. On preliminary data screening, cases with incomplete response were removed from data. Further assessment of normality and outliers was performed on the factor scores based on the critical ratio (i.e., for skewness and kurtosis to their standard error) and the Mahalanobis distance. Mahalanobis distance was used to identify the outliers by using AMOS software. It computes and tabulates the distance of every data from the center of all data distribution [19].The CFA was performed to examine the goodness of fit indices of the Malay OAKHQOL latent construct. Construct validity examines the degree to which a scale measures what it intends to measure [20]. Construct validity is achieved if the goodness of fit indices signify a model fit [20].The measurement of the model fit was checked with several goodness of fit indicators: comparative fit index (CFI), Tucker-Lewis index (TLI), incremental fit index (IFI), chi-squared/degree of freedom, and root mean square error of approximation (RMSEA) [12, 13, 21]. For approximate fit index, a value of more than 0.9 was taken for CFI, IFI, and TLI [21, 22]. Chi-squared/degree of freedom of less than 3 and RMSEA value of less than 0.08 were taken as indicators of an acceptable level [12, 13, 19].In addition to the overall evaluation of goodness of fit, the standardized factor loading (standardized regression weight) modification indices (MI) and squared multiple correlation (R2) were used as indicators to select which items should be removed in the model [12, 13]. MI suggested correlations between variables. A high MI value indicates redundancy in a pair of variables [12, 13]. Discriminant validity is also assessed by obtaining correlation values between the constructs. A correlation of more than 0.85 between constructs is considered to indicate poor discriminant validity [12, 13].Reliability analysis was measured using Cronbach’s alpha coefficient, composite reliability (CR), and average variance extracted (AVE). Reliability refers to the accuracy and precision of the measurement procedure. Cronbach’s alpha coefficient was measured using SPSS. Both CR and AVE were derived from CFA analysis and manually calculated based on published formula [19, 23]. A Cronbach’s alpha coefficient value of more than 0.7 and a CR equal to or greater than 0.6 represent a measure of satisfactory internal consistency [19, 24, 25]. AVE is the average percentage of variation explained by the variables in the construct or domain. The acceptable value for it was taken as more than 0.5 [19]. In this study, the test-retest reliability was not done due to time constraint and limited budget.The Pearson correlation test was performed to assess the criterion validity of the OAKHQOL. The test was done between the pain construct of the OAKHQOL and the pain construct of the WOMAC, as well as between the physical construct of the OAKHQOL and the functional construct of the WOMAC. The correlation coefficient of more than 0.5 but less than 0.8 was considered to be a good correlation [26].Known group validity is a method to support construct validity of a questionnaire. The method will evaluate the questionnaire ability to discriminate between the two groups known to differ on the variable of interest [27]. In this study, known group validity was assessed through gender, BMI, age groups of the patients, and Kellgren–Lawrence grading of the knee radiograph. We hypothesized that females, those aged more than 60 years [28], those having a BMI greater than 25 kg/m2, and those with more severe radiographic grading would have significant differences [10]. An independent t-test was used to analyze for gender, BMI, and age groups of the patients. One-way ANOVA test was used to analyze radiographic grading based on Kellgren–Lawrence classification. In the analysis for known group validity, the score for each domain was normalized to 0–100.


## 3. Results

### 3.1. Translation and Cultural Adaptation

We found that all the items in the Malay version questionnaire are relevant and appropriate to the Malaysian population. All the items were found to be acceptable, clear, and easy to understand in the face validity.


### 3.2. Psychometric Properties

A total of 191 patients participated in the study. The sociodemographic and knee OA disease characteristics of the participants are shown in Table1. The mean age was 57.8 (6.8) years and the majority were female. The Kellgren–Lawrence classification ranged from grade 0 to 4.Table 1
Sociodemographic and clinical characteristics of knee OA patients.
Variables Mean (SD) N (%) Age (year) 57.8 6.8 Gender: Male   63 (33) Female   128 (67) Education: Primary   30 (15.7) Secondary   132 (69.1) Tertiary   29 (15.2) Race: Malay   186 (97.4) Chinese   5 (2.6) BMI (kg/m2) 28.5 5.1 Duration of knee OA (year) 3.7 3.7 Knee joint affected Left   43 (22.5) Right   34 (17.8) Both   114 (59.7) Kellgren–Lawrence classification: 0   59 (30.9) 1   68 (35.6) 2   33 (17.3) 3   27 (14.1) 4   4 (2.1)


### 3.3. Descriptive Statistics of the Items

The items in the five constructs of OAKHQOL had missing data ranging from 0 to 3 values (0%–1.5%). However, the individual items concerning professional life, relationships, and sexual activities had 10 to 13 missing values. The missing values were replaced with the mean scores for the domain during the CFA. Normality assessment was done for the 40 items in the five constructs using histogram, box-plot, and measurement of skewness, which showed normal distribution. The absolute and percentage frequencies of the score for all the items were calculated and illustrated in Table2.Table 2
Absolute and percentage frequencies of score for all items.
Score item 0 1 2 3 4 5 6 7 8 9 10 Total Py1 Freq 11 24 20 24 26 38 12 20 7 3 6 191 % 5.8 12.6 10.5 12.6 13.6 19.9 6.3 10.5 3.7 1.6 3.1 100 Py2 Freq 9 14 25 23 15 37 17 21 13 10 7 191 % 4.7 7.3 13.1 12.0 7.9 19.4 8.9 11.0 6.8 5.2 3.7 100 Py3 Freq 11 15 16 12 23 32 25 19 16 15 7 191 % 5.8 7.9 8.4 6.3 12.0 16.8 13.1 9.9 8.4 7.9 3.7 100 Py4 Freq 8 10 11 21 22 45 20 23 15 12 4 191 % 4.2 5.2 5.8 11.0 11.5 23.6 10.5 12.0 7.9 6.3 2.1 100 Py5 Freq 7 8 12 15 20 23 32 33 20 15 6 191 % 3.7 4.2 6.3 7.9 10.5 12.0 16.8 17.3 10.5 7.9 3.1 100 Py6 Freq 49 32 25 23 14 22 9 7 4 4 2 191 % 25.7 16.8 13.1 12.0 7.3 11.5 4.7 3.7 2.1 2.1 1.0 100 Py7 Freq 35 22 21 16 20 26 22 11 10 7 1 191 % 18.3 11.5 11.0 8.4 10.5 13.6 11.5 5.8 5.2 3.7 0.5 100 Py8 Freq 35 24 18 16 14 28 16 11 15 9 5 191 % 18.3 12.6 9.4 8.4 7.3 14.7 8.4 5.8 7.9 4.7 2.6 100 Py9 Freq 2 13 17 11 20 32 28 21 17 23 7 191 % 1.0 6.8 8.9 5.8 10.5 16.8 14.7 11.0 8.9 12.0 3.7 100 Py10 Freq 18 14 19 16 17 36 27 16 12 10 6 191 % 9.4 7.3 9.9 8.4 8.9 18.8 14.1 8.4 6.3 5.2 3.1 100 Py11 Freq 33 15 14 14 31 25 14 12 12 7 4 191 % 17.3 7.9 7.3 7.3 16.2 13.1 7.3 6.3 6.3 3.7 7.3 100 Py13 Freq 45 24 23 18 17 27 17 13 2 2 3 191 % 23.6 12.6 12.0 9.4 8.9 14.1 8.9 6.8 1.1 1.1 1.6 100 Py14 Freq 31 17 22 20 21 32 16 15 11 3 3 191 % 16.2 8.9 11.5 10.5 11.0 16.8 8.4 7.9 5.8 1.6 1.6 100 M15 Freq 25 19 21 19 22 29 23 13 8 9 3 191 % 13.1 9.9 11.0 9.9 11.5 15.2 12.0 6.8 4.2 4.7 1.6 100 M16 Freq 20 21 19 18 14 27 25 20 13 7 7 191 % 10.5 11.0 9.9 9.4 7.3 14.1 13.1 10.5 6.8 3.7 3.7 100 M17 Freq 18 26 21 16 17 26 20 18 16 8 5 191 % 9.4 13.6 11.0 8.4 8.9 13.6 10.5 9.4 8.4 4.2 2.6 100 M18 Freq 40 20 18 20 17 22 16 12 15 7 4 191 % 20.9 10.5 9.4 10.5 8.9 11.5 8.4 6.3 7.9 3.7 2.1 100 M19 Freq 36 28 18 15 18 29 17 12 8 7 3 191 % 18.8 14.7 9.4 7.9 9.4 15.2 8.9 6.3 4.2 3.7 1.6 100 M20 Freq 33 27 22 17 16 34 15 9 6 9 3 191 % 17.3 14.1 11.5 8.9 8.4 17.8 7.9 4.7 3.1 4.7 1.6 100 M21 Freq 51 27 13 22 7 29 11 13 9 7 2 191 % 26.7 14.1 6.8 11.5 3.7 15.2 5.8 6.8 4.7 3.7 1.0 100 Py24 Freq 6 11 19 19 18 27 27 19 22 15 8 191 % 3.1 5.8 9.9 9.9 9.4 14.1 14.1 9.9 11.5 7.9 4.2 100 Py25 Freq 100 21 16 10 6 14 4 5 3 4 8 191 % 52.4 11.0 8.4 5.2 3.1 7.3 2.1 2.6 1.6 2.1 4.2 100 Pn26 Freq 9 16 23 24 20 30 13 21 15 12 8 191 % 4.7 8.4 12.0 12.6 10.5 15.7 6.8 11.0 7.9 6.3 4.2 100 Pn27 Freq 20 14 25 25 16 31 18 16 14 6 6 191 % 10.5 7.3 13.1 13.1 8.4 16.2 9.4 8.4 7.3 3.1 3.1 100 Py28 Freq 46 31 15 18 12 27 13 12 7 7 3 191 % 24.1 16.2 7.9 9.4 6.3 14.1 6.8 6.3 3.7 3.7 1.6 100 M29 Freq 39 24 18 17 18 30 22 4 9 8 2 191 % 20.4 12.6 9.4 8.9 9.4 15.7 11.5 2.1 4.7 4.2 1.0 100 Sf30 Freq 20 8 24 17 14 34 15 8 14 16 21 191 % 10.5 4.2 12.6 8.9 7.3 17.8 7.9 4.2 7.3 8.4 11.0 100 Sf31 Freq 17 12 18 20 14 36 18 6 7 19 24 191 % 8.9 6.3 9.4 10.5 7.3 18.8 9.4 3.1 3.7 9.9 12.6 100 Sf32 Freq 12 12 12 19 24 28 16 9 15 18 26 191 % 6.3 6.3 6.3 9.9 12.6 14.7 8.4 4.7 7.9 9.4 13.6 100 Pn33 Freq 44 24 21 13 12 32 16 9 14 4 2 191 % 23.0 12.6 11.0 6.8 6.3 16.8 8.4 4.7 7.3 2.1 1.0 100 Pn34 Freq 51 24 21 11 17 27 13 10 13 3 1 191 % 26.7 12.6 11.0 5.8 8.9 14.1 6.8 5.2 6.8 1.6 0.5 100 M35 Freq 19 33 30 17 13 37 11 12 8 6 5 191 % 9.9 17.3 15.7 8.9 6.8 19.4 5.8 6.3 4.2 3.1 2.6 100 M36 Freq 40 29 23 17 20 30 11 7 9 4 1 191 % 20.9 15.2 12.0 8.9 10.5 15.7 5.8 3.7 4.7 2.1 0.5 100 M37 Freq 68 29 19 15 15 26 7 4 3 5 0 191 % 35.6 15.2 9.9 7.9 7.9 13.6 3.7 2.1 1.6 2.6 0 100 M38 Freq 37 28 20 18 17 34 12 9 9 6 1 191 % 19.4 14.7 10.5 9.4 8.9 17.8 6.3 4.7 4.7 3.1 5 100 Sp39 Freq 9 11 12 16 14 23 17 23 16 16 34 191 % 4.7 5.8 6.3 8.4 7.3 12.0 8.9 12.0 8.4 8.4 17.8 100 Sp40 Freq 9 9 15 11 13 39 14 12 26 21 22 191 % 4.7 4.7 7.9 5.8 6.8 20.4 7.3 6.3 13.6 11.0 11.5 100 M41 Freq 45 24 22 17 11 37 13 6 6 7 3 191 % 23.6 12.6 11.5 8.9 5.8 19.4 6.8 3.1 3.1 3.7 1.6 100 sp42 Freq 10 6 16 12 9 23 13 16 14 20 52 191 % 5.2 3.1 8.4 6.3 4.7 12.0 6.8 8.4 7.3 10.5 27.2 100 sp43 Freq 11 10 13 15 12 28 16 15 19 18 34 191 % 5.8 5.2 6.8 7.9 6.3 14.7 8.4 7.9 9.9 9.4 17.8 100 Py: physical activity; m: mental health; pn: pain; sf: social functioning; sp: social support.


### 3.4. Confirmatory Analysis

Confirmatory factor analysis was performed with one-step strategy. Confirmatory analysis showed that the original five-factor model of the OAKHQOL (40 items) was not fit (Table3). Five items (py25, m36, m37, m38, and m16) were removed one by one due to low factor loadings, as shown in Model A. Eight items were set as free parameter estimates, one pair at a time (py1-py2, py7-py8, py4-py5, and pn34-pn33), based on high MI (greater than 15) as shown in Model C. Further item deletion was done based on MI and factor loadings (py3, py9, m29, py24, sp39, py14, and py13) until the final model, which consists of a five factors with 28 items, signified a model fit (Table 3). The final model consists of five constructs: physical activity (10 items), mental health (eight items), social functioning (three items), social support (three items), and pain (four items). Six items in the physical activity, five items in the mental health, and one item in the social support were removed. The goodness of fit indices indicated that the model had a good construct (CFI = 0.915, TLI = 0.905, IFI = 0.916, chi-squared/degree of freedom = 1.953, and RMSEA = 0.071) (Table 3).Table 3
Fitness level of models.
5-factor model RMSEA CFI IFI TLI ChiSquare/df Actions taken Original:(40 item) 0.100 0.770 0.772 0.754 2.908  Model A:35 items 0.094 0.826 0.827 0.811 2.680 Delete py25, m36, m37, m38 m16  Model B:35 items 0.094 0.843 0.844 0.829 2.680 Correlate between the errors py7-py8 py4-py5 py1-py2 pn33-pn34  Model C30 items 0.090 0.901 0.902 0.890 2.061 Delete: py3, py9, m29, py24, sp 39  Final model:28 items 0.071 0.915 0.916 0.905 1.953 Delete py14 and py13 CFI: comparative fit index; TLI: Tucker-Lewis index; IFI: incremental fit index; RMSEA: root mean squared error of approximation.The initial model before fit was shown in Figure1. The correlation between factors was illustrated in Figure 2. The standardized factor loadings were from 0.5 to 0.9, indicating that all items contributed highly to the construct measures. The MI values were less than 10, and the correlation between each pair of latent constructs was less than 0.85, which is acceptable (Figure 2) [19].Figure 1
The initial AMOS graphic shows the goodness of fit indexes, respective path coefficient, factor loading, andR2. PHY: physical activity, SOCF: social functioning, SOCP: social support, MEN: mental health, PAN: pain.Figure 2
The AMOS graphic shows the goodness of fit indexes, respective path coefficient, factor loading, andR2. The final model shows 5 constructs and 28 items. PHY: physical activity, SOCF: social functioning, SOCP: social support, MEN: mental health, PAN: pain.


### 3.5. Reliability

The reliability analysis showed that the Cronbach’s alpha coefficient value for each construct was greater than 0.7 (Table4). The CR and AVE of each construct also showed that the final construct had a good measure of reliability. The result was achieved by using one-step estimation strategy.Table 4
Reliability and confirmatory factor analysis of the Malay version OAKHQOL.
Construct Item Factor loading Cronbach alpha CR AVE Physical activity py1 0.774 0.933 0.915 0.743 py2 0.736 py4 0.653 py5 0.646 py6 0.672 py7 0.771 py8 0.716 py10 0.804 py11 0.679 py28 0.742  Mental m15 0.773 0.919 0.921 0.796 m17 0.754 m18 0.726 m19 0.899 m20 0.910 m21 0.798 m35 0.656 m41 0.608  Social functioning sf30 0.756 0.865 0.867 0.867 sf31 0.851 sf32 0.871  Social support sp40 0.786 0.888 0.890 0.686 sp42 0.871 sp43 0.901  Pain pn34 0.538 0.809 0.819 0.540 pn33 0.657 pn27 0.834 pn26 0.847 CR: construct reliability; AVE: average variance extracted.Table5 shows the Pearson’s correlation coefficients between the physical activity construct of the OAKHQOL and the functional construct of the WOMAC (r = 0.72) and between the pain construct of the OAKHQOL and pain construct of the WOMAC (r = 0.55). These results indicated that the OAKHQOL had acceptable criterion validity.Table 5
Pearson correlation coefficient.
r p value Physical activity domain OAKHQOL and functional domain WOMAC 0.72 <0.001 Pain domain WOMAC and pain domain OAKHQOL 0.55 <0.001 Correlation is significant at the 0.05 level (2-tailed).


### 3.6. Known Group Validity

The results for the known group validity of the OAKHQOL are shown in Table6. We found significant differences among the BMI groups (BMI ≤ 25 kg/m2 and >25 kg/m2) in the physical activity (p = 0.009), mental (p = 0.040), and pain domains (p = 0.009). We also found significant differences among the groups based on OA severity according to radiographic grading in the physical activity (p = 0.002) and pain domains (p = 0.043). Thus, groups who had greater disease severity based on radiography had worse scores. The scores of the pain domain for the age groups (age ≤ 60 years compared to those age > 60 years) were also significant. There were no differences observed for the social support and social function domains.Table 6
Known group validity of the Malay version OAKHQOL.
Variables  Physical Mental Pain Social functioning Social support N Mean SD p value Mean SD p value Mean SD p value Mean SD p value Mean SD p value Gender:    0.208   0.370   0.890   0.761   0.328 Male 63 37.5 17.7  33.8 22.4  37.7 20.9  49.9 29.2  57.4 27.4 Female 128 41.8 21.5  36.7 22.2  38.2 23.5  51.2 27.4  61.5 28.3 Age:    0.321   0.208   0.025   0.767   0.929 ≤60 years 161 39.7 19.9  34.8 22.2  36.7 21.9  51.1 28.2  60.3 27.9 >60 years 30 43.6 22.2  40.1 22.5  45.1 25.5  49.2 26.9  59.8 29.2 BMI    0.009   0.040   0.009   0.434   0.940 <25 50 32.5   30.2   30.9 20.2  53.5 29.3  59.9 28.6 ≥25 141 42.3   37.7   40.5 22.9  49.9 27.4  60.2 27.9 KL grading    0.002   0.125   0.043   0.527   0.424 0 59 37.8 18.1  33.6 22.4  38.4 22.9  47.6 30.1  58.1 27.9 1 68 36.4 19.2  32.0 20.7  32.6 21.1  51.2 29.3  59.9 29.5 2 33 42.7 21.1  41.2 21.1  39.3 20.8  57.5 21.9  64.9 24.9 3 27 50.0 22.6  41.7 26.0  47.5 24.7  47.7 26.4  56.7 28.9 4 4 69.3 13.5  46.3 13.3  50.0 29.8  56.7 24.6  80.9 13.4 BMI: body mass index (kg/m2), KL: Kellgren–Lawrence grading of knee X-ray.Table 7
Prevalidation of Malay version of OAKHQOL questionnaire (40 items).
Domain 1 Saya mengalami kesusahan untuk berjalan py1 2 Saya mengalami kesusahan untuk tunduk atau meluruskan badan/bangun semula py2 3 Saya mengalami kesusahan untuk membawa barang yang berat py3 4 Saya mengalami kesusahan untuk menuruni tangga py4 5 Saya mengalami kesusahan untuk menaiki tangga py5 6 Saya mengalami kesusahan untuk mandi py6 7 Saya mengalami kesusahan untuk berpakaian lengkap (seperti memakai stoking, kasut, seluar dan sebagainya) py7 8 Saya mengalami kesusahan untuk memotong kuku kaki py8 9 Saya mengalami kesusahan untuk bergerak selepas lama berada dalam kedudukan yang sama py9 10 Saya mengalami kesusahan untuk masuk dan keluar daripada kereta py10 11 Saya mengalami kesusahan untuk menggunakan kenderaan awam (bas, teksi dsb) py11 12 Saya perlukan masa untuk bersendiri/saya perlu bersendiri py13 13 Saya memerlukan masa yang lebih lama untuk melakukan sesuatu perkara py14 14 Saya kurang bersemangat disebabkan sakit m15 15 Saya risau jika saya perlu bergantung kepada orang lain m16 16 Saya risau menjadi tidak berkemampuan m17 17 Saya merasa malu apabila orang melihat saya m18 18 Saya berasa gelisah m19 19 Saya berasa tertekan m20 20 Saya merasakan kehidupan keluarga saya terjejas m21 21 Saya mengalami kesusahan untuk berada dikedudukan yang sama untuk jangkamasa yang lama (duduk, berdiri, tidak bergerak dsb) py24 22 Saya memerlukan tongkat atau alat bantu untuk berjalan py25 23 Saya mengalami kesakitan (kekerapan) pn26 24 Saya mengalami kesakitan (keterukan) pn27 25 Saya memerlukan pertolongan untuk membuat sesuatu seperti kerja rumah dan membeli belah py28 26 Saya rasa lebih tua daripada umur saya m29 27 Saya mampu/boleh merancang projek/program untuk jangkamasa yang panjang sf30 28 Saya keluar rumah sekerap mana yang saya suka sf31 29 Saya melayan tetamu di rumah sebanyak mana yang saya suka sf32 30 Saya mengalami kesukaran untuk tidur atau tidur semula kerana sakit pn33 31 Saya terjaga disebabkan sakit pn34 32 Saya tertanya-tanya apa yang bakal berlaku/kan terjadi kepada saya m35 33 Saya pemarah/mudah marah atau agresif m36 34 Saya rasa saya menyakiti hati mereka yang rapat dengan saya m37 35 Saya merasa risau tentang kesan sampingan rawatan saya m38 36 Saya boleh berkongsi dengan orang lain tentang kesukaran yang saya alami disebabkan penyakit sendi (arthritis) sebanyak mana yang saya suka sp39 37 Saya merasakan orang lain faham tentang kesusahan yang saya alami disebabkan penyakit sendi (arthritis) saya sp40 38 Saya merasa malu untuk meminta bantuan/pertolongan jika perlu m41 39 Saya rasa saya diberi sokongan oleh orang yang rapat dengan saya (pasangan dan keluarga) sp42 40 Saya rasa saya diberi sokongan oleh orang yang berada di sekeliling saya (kawan dan jiran) sp43 Py: physical activity; m: mental; pn: pain; sf: social functioning; sp: social support.Table 8
Prevalidation of English version of OAKHQOL questionnaire (40 items).
Domain 1 I have difficulty walking py1 2 I have difficulty bending down or straightening up py2 3 I have difficulty carrying heavy things py3 4 I have difficulty going down stairs py4 5 I have difficulty climbing stairs py5 6 I have difficulty taking a bath py6 7 I have difficulty getting dressed py7 8 I have difficulty cutting my toe-nails py8 9 I have difficulty getting going again after staying in the same position for a long time py9 10 I have difficulty getting in and out of a car py10 11 I have difficulty using public transport py11 12 I have to pace myself py13 13 I take more time to do things py14 14 My spirits are low because of the pain m15 15 I worry about being dependent on others m16 16 I worry about being disabled m17 17 I feel embarrassed when people look at me m18 18 I am anxious m19 19 I am depressed m20 20 I feel my family life is being affected m21 21 I have difficulty staying in the same position for a long time py24 22 I need a walking stick/cane or crutches to walk py25 23 I have pain (describe frequency) pn26 24 I have pain (describe intensity) pn27 25 I need help for things like housework and shopping py28 26 I feel older than my age m29 27 I am able to plan projects for the long term sf30 28 I get out of the house as much as I like sf31 29 I entertain at home as much as I like sf32 30 I have difficulty getting to sleep or getting back to sleep because of pain pn33 31 I wake up because of pain pn34 32 I wonder what will become of me m35 33 I am irritable or aggressive m36 34 I feel I annoy those close to me m37 35 I am worried about the side effects of my treatment m38 36 I can talk to others about the difficulties I have due to my arthritis as much as I like sp39 37 I feel others understand the difficulties I have because of my arthritis sp40 38 I am embarrassed to ask for help if I need it m41 39 I feel supported by people close to me sp42 40 I feel supported by those around me sp43 Py: physical activity; m: mental; pn: pain; sf: social functioning; sp: social support.


## 3.1. Translation and Cultural Adaptation

We found that all the items in the Malay version questionnaire are relevant and appropriate to the Malaysian population. All the items were found to be acceptable, clear, and easy to understand in the face validity.


## 3.2. Psychometric Properties

A total of 191 patients participated in the study. The sociodemographic and knee OA disease characteristics of the participants are shown in Table1. The mean age was 57.8 (6.8) years and the majority were female. The Kellgren–Lawrence classification ranged from grade 0 to 4.Table 1
Sociodemographic and clinical characteristics of knee OA patients.
Variables Mean (SD) N (%) Age (year) 57.8 6.8 Gender: Male   63 (33) Female   128 (67) Education: Primary   30 (15.7) Secondary   132 (69.1) Tertiary   29 (15.2) Race: Malay   186 (97.4) Chinese   5 (2.6) BMI (kg/m2) 28.5 5.1 Duration of knee OA (year) 3.7 3.7 Knee joint affected Left   43 (22.5) Right   34 (17.8) Both   114 (59.7) Kellgren–Lawrence classification: 0   59 (30.9) 1   68 (35.6) 2   33 (17.3) 3   27 (14.1) 4   4 (2.1)


## 3.3. Descriptive Statistics of the Items

The items in the five constructs of OAKHQOL had missing data ranging from 0 to 3 values (0%–1.5%). However, the individual items concerning professional life, relationships, and sexual activities had 10 to 13 missing values. The missing values were replaced with the mean scores for the domain during the CFA. Normality assessment was done for the 40 items in the five constructs using histogram, box-plot, and measurement of skewness, which showed normal distribution. The absolute and percentage frequencies of the score for all the items were calculated and illustrated in Table2.Table 2
Absolute and percentage frequencies of score for all items.
Score item 0 1 2 3 4 5 6 7 8 9 10 Total Py1 Freq 11 24 20 24 26 38 12 20 7 3 6 191 % 5.8 12.6 10.5 12.6 13.6 19.9 6.3 10.5 3.7 1.6 3.1 100 Py2 Freq 9 14 25 23 15 37 17 21 13 10 7 191 % 4.7 7.3 13.1 12.0 7.9 19.4 8.9 11.0 6.8 5.2 3.7 100 Py3 Freq 11 15 16 12 23 32 25 19 16 15 7 191 % 5.8 7.9 8.4 6.3 12.0 16.8 13.1 9.9 8.4 7.9 3.7 100 Py4 Freq 8 10 11 21 22 45 20 23 15 12 4 191 % 4.2 5.2 5.8 11.0 11.5 23.6 10.5 12.0 7.9 6.3 2.1 100 Py5 Freq 7 8 12 15 20 23 32 33 20 15 6 191 % 3.7 4.2 6.3 7.9 10.5 12.0 16.8 17.3 10.5 7.9 3.1 100 Py6 Freq 49 32 25 23 14 22 9 7 4 4 2 191 % 25.7 16.8 13.1 12.0 7.3 11.5 4.7 3.7 2.1 2.1 1.0 100 Py7 Freq 35 22 21 16 20 26 22 11 10 7 1 191 % 18.3 11.5 11.0 8.4 10.5 13.6 11.5 5.8 5.2 3.7 0.5 100 Py8 Freq 35 24 18 16 14 28 16 11 15 9 5 191 % 18.3 12.6 9.4 8.4 7.3 14.7 8.4 5.8 7.9 4.7 2.6 100 Py9 Freq 2 13 17 11 20 32 28 21 17 23 7 191 % 1.0 6.8 8.9 5.8 10.5 16.8 14.7 11.0 8.9 12.0 3.7 100 Py10 Freq 18 14 19 16 17 36 27 16 12 10 6 191 % 9.4 7.3 9.9 8.4 8.9 18.8 14.1 8.4 6.3 5.2 3.1 100 Py11 Freq 33 15 14 14 31 25 14 12 12 7 4 191 % 17.3 7.9 7.3 7.3 16.2 13.1 7.3 6.3 6.3 3.7 7.3 100 Py13 Freq 45 24 23 18 17 27 17 13 2 2 3 191 % 23.6 12.6 12.0 9.4 8.9 14.1 8.9 6.8 1.1 1.1 1.6 100 Py14 Freq 31 17 22 20 21 32 16 15 11 3 3 191 % 16.2 8.9 11.5 10.5 11.0 16.8 8.4 7.9 5.8 1.6 1.6 100 M15 Freq 25 19 21 19 22 29 23 13 8 9 3 191 % 13.1 9.9 11.0 9.9 11.5 15.2 12.0 6.8 4.2 4.7 1.6 100 M16 Freq 20 21 19 18 14 27 25 20 13 7 7 191 % 10.5 11.0 9.9 9.4 7.3 14.1 13.1 10.5 6.8 3.7 3.7 100 M17 Freq 18 26 21 16 17 26 20 18 16 8 5 191 % 9.4 13.6 11.0 8.4 8.9 13.6 10.5 9.4 8.4 4.2 2.6 100 M18 Freq 40 20 18 20 17 22 16 12 15 7 4 191 % 20.9 10.5 9.4 10.5 8.9 11.5 8.4 6.3 7.9 3.7 2.1 100 M19 Freq 36 28 18 15 18 29 17 12 8 7 3 191 % 18.8 14.7 9.4 7.9 9.4 15.2 8.9 6.3 4.2 3.7 1.6 100 M20 Freq 33 27 22 17 16 34 15 9 6 9 3 191 % 17.3 14.1 11.5 8.9 8.4 17.8 7.9 4.7 3.1 4.7 1.6 100 M21 Freq 51 27 13 22 7 29 11 13 9 7 2 191 % 26.7 14.1 6.8 11.5 3.7 15.2 5.8 6.8 4.7 3.7 1.0 100 Py24 Freq 6 11 19 19 18 27 27 19 22 15 8 191 % 3.1 5.8 9.9 9.9 9.4 14.1 14.1 9.9 11.5 7.9 4.2 100 Py25 Freq 100 21 16 10 6 14 4 5 3 4 8 191 % 52.4 11.0 8.4 5.2 3.1 7.3 2.1 2.6 1.6 2.1 4.2 100 Pn26 Freq 9 16 23 24 20 30 13 21 15 12 8 191 % 4.7 8.4 12.0 12.6 10.5 15.7 6.8 11.0 7.9 6.3 4.2 100 Pn27 Freq 20 14 25 25 16 31 18 16 14 6 6 191 % 10.5 7.3 13.1 13.1 8.4 16.2 9.4 8.4 7.3 3.1 3.1 100 Py28 Freq 46 31 15 18 12 27 13 12 7 7 3 191 % 24.1 16.2 7.9 9.4 6.3 14.1 6.8 6.3 3.7 3.7 1.6 100 M29 Freq 39 24 18 17 18 30 22 4 9 8 2 191 % 20.4 12.6 9.4 8.9 9.4 15.7 11.5 2.1 4.7 4.2 1.0 100 Sf30 Freq 20 8 24 17 14 34 15 8 14 16 21 191 % 10.5 4.2 12.6 8.9 7.3 17.8 7.9 4.2 7.3 8.4 11.0 100 Sf31 Freq 17 12 18 20 14 36 18 6 7 19 24 191 % 8.9 6.3 9.4 10.5 7.3 18.8 9.4 3.1 3.7 9.9 12.6 100 Sf32 Freq 12 12 12 19 24 28 16 9 15 18 26 191 % 6.3 6.3 6.3 9.9 12.6 14.7 8.4 4.7 7.9 9.4 13.6 100 Pn33 Freq 44 24 21 13 12 32 16 9 14 4 2 191 % 23.0 12.6 11.0 6.8 6.3 16.8 8.4 4.7 7.3 2.1 1.0 100 Pn34 Freq 51 24 21 11 17 27 13 10 13 3 1 191 % 26.7 12.6 11.0 5.8 8.9 14.1 6.8 5.2 6.8 1.6 0.5 100 M35 Freq 19 33 30 17 13 37 11 12 8 6 5 191 % 9.9 17.3 15.7 8.9 6.8 19.4 5.8 6.3 4.2 3.1 2.6 100 M36 Freq 40 29 23 17 20 30 11 7 9 4 1 191 % 20.9 15.2 12.0 8.9 10.5 15.7 5.8 3.7 4.7 2.1 0.5 100 M37 Freq 68 29 19 15 15 26 7 4 3 5 0 191 % 35.6 15.2 9.9 7.9 7.9 13.6 3.7 2.1 1.6 2.6 0 100 M38 Freq 37 28 20 18 17 34 12 9 9 6 1 191 % 19.4 14.7 10.5 9.4 8.9 17.8 6.3 4.7 4.7 3.1 5 100 Sp39 Freq 9 11 12 16 14 23 17 23 16 16 34 191 % 4.7 5.8 6.3 8.4 7.3 12.0 8.9 12.0 8.4 8.4 17.8 100 Sp40 Freq 9 9 15 11 13 39 14 12 26 21 22 191 % 4.7 4.7 7.9 5.8 6.8 20.4 7.3 6.3 13.6 11.0 11.5 100 M41 Freq 45 24 22 17 11 37 13 6 6 7 3 191 % 23.6 12.6 11.5 8.9 5.8 19.4 6.8 3.1 3.1 3.7 1.6 100 sp42 Freq 10 6 16 12 9 23 13 16 14 20 52 191 % 5.2 3.1 8.4 6.3 4.7 12.0 6.8 8.4 7.3 10.5 27.2 100 sp43 Freq 11 10 13 15 12 28 16 15 19 18 34 191 % 5.8 5.2 6.8 7.9 6.3 14.7 8.4 7.9 9.9 9.4 17.8 100 Py: physical activity; m: mental health; pn: pain; sf: social functioning; sp: social support.


## 3.4. Confirmatory Analysis

Confirmatory factor analysis was performed with one-step strategy. Confirmatory analysis showed that the original five-factor model of the OAKHQOL (40 items) was not fit (Table3). Five items (py25, m36, m37, m38, and m16) were removed one by one due to low factor loadings, as shown in Model A. Eight items were set as free parameter estimates, one pair at a time (py1-py2, py7-py8, py4-py5, and pn34-pn33), based on high MI (greater than 15) as shown in Model C. Further item deletion was done based on MI and factor loadings (py3, py9, m29, py24, sp39, py14, and py13) until the final model, which consists of a five factors with 28 items, signified a model fit (Table 3). The final model consists of five constructs: physical activity (10 items), mental health (eight items), social functioning (three items), social support (three items), and pain (four items). Six items in the physical activity, five items in the mental health, and one item in the social support were removed. The goodness of fit indices indicated that the model had a good construct (CFI = 0.915, TLI = 0.905, IFI = 0.916, chi-squared/degree of freedom = 1.953, and RMSEA = 0.071) (Table 3).Table 3
Fitness level of models.
5-factor model RMSEA CFI IFI TLI ChiSquare/df Actions taken Original:(40 item) 0.100 0.770 0.772 0.754 2.908  Model A:35 items 0.094 0.826 0.827 0.811 2.680 Delete py25, m36, m37, m38 m16  Model B:35 items 0.094 0.843 0.844 0.829 2.680 Correlate between the errors py7-py8 py4-py5 py1-py2 pn33-pn34  Model C30 items 0.090 0.901 0.902 0.890 2.061 Delete: py3, py9, m29, py24, sp 39  Final model:28 items 0.071 0.915 0.916 0.905 1.953 Delete py14 and py13 CFI: comparative fit index; TLI: Tucker-Lewis index; IFI: incremental fit index; RMSEA: root mean squared error of approximation.The initial model before fit was shown in Figure1. The correlation between factors was illustrated in Figure 2. The standardized factor loadings were from 0.5 to 0.9, indicating that all items contributed highly to the construct measures. The MI values were less than 10, and the correlation between each pair of latent constructs was less than 0.85, which is acceptable (Figure 2) [19].Figure 1
The initial AMOS graphic shows the goodness of fit indexes, respective path coefficient, factor loading, andR2. PHY: physical activity, SOCF: social functioning, SOCP: social support, MEN: mental health, PAN: pain.Figure 2
The AMOS graphic shows the goodness of fit indexes, respective path coefficient, factor loading, andR2. The final model shows 5 constructs and 28 items. PHY: physical activity, SOCF: social functioning, SOCP: social support, MEN: mental health, PAN: pain.


## 3.5. Reliability

The reliability analysis showed that the Cronbach’s alpha coefficient value for each construct was greater than 0.7 (Table4). The CR and AVE of each construct also showed that the final construct had a good measure of reliability. The result was achieved by using one-step estimation strategy.Table 4
Reliability and confirmatory factor analysis of the Malay version OAKHQOL.
Construct Item Factor loading Cronbach alpha CR AVE Physical activity py1 0.774 0.933 0.915 0.743 py2 0.736 py4 0.653 py5 0.646 py6 0.672 py7 0.771 py8 0.716 py10 0.804 py11 0.679 py28 0.742  Mental m15 0.773 0.919 0.921 0.796 m17 0.754 m18 0.726 m19 0.899 m20 0.910 m21 0.798 m35 0.656 m41 0.608  Social functioning sf30 0.756 0.865 0.867 0.867 sf31 0.851 sf32 0.871  Social support sp40 0.786 0.888 0.890 0.686 sp42 0.871 sp43 0.901  Pain pn34 0.538 0.809 0.819 0.540 pn33 0.657 pn27 0.834 pn26 0.847 CR: construct reliability; AVE: average variance extracted.Table5 shows the Pearson’s correlation coefficients between the physical activity construct of the OAKHQOL and the functional construct of the WOMAC (r = 0.72) and between the pain construct of the OAKHQOL and pain construct of the WOMAC (r = 0.55). These results indicated that the OAKHQOL had acceptable criterion validity.Table 5
Pearson correlation coefficient.
r p value Physical activity domain OAKHQOL and functional domain WOMAC 0.72 <0.001 Pain domain WOMAC and pain domain OAKHQOL 0.55 <0.001 Correlation is significant at the 0.05 level (2-tailed).


## 3.6. Known Group Validity

The results for the known group validity of the OAKHQOL are shown in Table6. We found significant differences among the BMI groups (BMI ≤ 25 kg/m2 and >25 kg/m2) in the physical activity (p = 0.009), mental (p = 0.040), and pain domains (p = 0.009). We also found significant differences among the groups based on OA severity according to radiographic grading in the physical activity (p = 0.002) and pain domains (p = 0.043). Thus, groups who had greater disease severity based on radiography had worse scores. The scores of the pain domain for the age groups (age ≤ 60 years compared to those age > 60 years) were also significant. There were no differences observed for the social support and social function domains.Table 6
Known group validity of the Malay version OAKHQOL.
Variables  Physical Mental Pain Social functioning Social support N Mean SD p value Mean SD p value Mean SD p value Mean SD p value Mean SD p value Gender:    0.208   0.370   0.890   0.761   0.328 Male 63 37.5 17.7  33.8 22.4  37.7 20.9  49.9 29.2  57.4 27.4 Female 128 41.8 21.5  36.7 22.2  38.2 23.5  51.2 27.4  61.5 28.3 Age:    0.321   0.208   0.025   0.767   0.929 ≤60 years 161 39.7 19.9  34.8 22.2  36.7 21.9  51.1 28.2  60.3 27.9 >60 years 30 43.6 22.2  40.1 22.5  45.1 25.5  49.2 26.9  59.8 29.2 BMI    0.009   0.040   0.009   0.434   0.940 <25 50 32.5   30.2   30.9 20.2  53.5 29.3  59.9 28.6 ≥25 141 42.3   37.7   40.5 22.9  49.9 27.4  60.2 27.9 KL grading    0.002   0.125   0.043   0.527   0.424 0 59 37.8 18.1  33.6 22.4  38.4 22.9  47.6 30.1  58.1 27.9 1 68 36.4 19.2  32.0 20.7  32.6 21.1  51.2 29.3  59.9 29.5 2 33 42.7 21.1  41.2 21.1  39.3 20.8  57.5 21.9  64.9 24.9 3 27 50.0 22.6  41.7 26.0  47.5 24.7  47.7 26.4  56.7 28.9 4 4 69.3 13.5  46.3 13.3  50.0 29.8  56.7 24.6  80.9 13.4 BMI: body mass index (kg/m2), KL: Kellgren–Lawrence grading of knee X-ray.Table 7
Prevalidation of Malay version of OAKHQOL questionnaire (40 items).
Domain 1 Saya mengalami kesusahan untuk berjalan py1 2 Saya mengalami kesusahan untuk tunduk atau meluruskan badan/bangun semula py2 3 Saya mengalami kesusahan untuk membawa barang yang berat py3 4 Saya mengalami kesusahan untuk menuruni tangga py4 5 Saya mengalami kesusahan untuk menaiki tangga py5 6 Saya mengalami kesusahan untuk mandi py6 7 Saya mengalami kesusahan untuk berpakaian lengkap (seperti memakai stoking, kasut, seluar dan sebagainya) py7 8 Saya mengalami kesusahan untuk memotong kuku kaki py8 9 Saya mengalami kesusahan untuk bergerak selepas lama berada dalam kedudukan yang sama py9 10 Saya mengalami kesusahan untuk masuk dan keluar daripada kereta py10 11 Saya mengalami kesusahan untuk menggunakan kenderaan awam (bas, teksi dsb) py11 12 Saya perlukan masa untuk bersendiri/saya perlu bersendiri py13 13 Saya memerlukan masa yang lebih lama untuk melakukan sesuatu perkara py14 14 Saya kurang bersemangat disebabkan sakit m15 15 Saya risau jika saya perlu bergantung kepada orang lain m16 16 Saya risau menjadi tidak berkemampuan m17 17 Saya merasa malu apabila orang melihat saya m18 18 Saya berasa gelisah m19 19 Saya berasa tertekan m20 20 Saya merasakan kehidupan keluarga saya terjejas m21 21 Saya mengalami kesusahan untuk berada dikedudukan yang sama untuk jangkamasa yang lama (duduk, berdiri, tidak bergerak dsb) py24 22 Saya memerlukan tongkat atau alat bantu untuk berjalan py25 23 Saya mengalami kesakitan (kekerapan) pn26 24 Saya mengalami kesakitan (keterukan) pn27 25 Saya memerlukan pertolongan untuk membuat sesuatu seperti kerja rumah dan membeli belah py28 26 Saya rasa lebih tua daripada umur saya m29 27 Saya mampu/boleh merancang projek/program untuk jangkamasa yang panjang sf30 28 Saya keluar rumah sekerap mana yang saya suka sf31 29 Saya melayan tetamu di rumah sebanyak mana yang saya suka sf32 30 Saya mengalami kesukaran untuk tidur atau tidur semula kerana sakit pn33 31 Saya terjaga disebabkan sakit pn34 32 Saya tertanya-tanya apa yang bakal berlaku/kan terjadi kepada saya m35 33 Saya pemarah/mudah marah atau agresif m36 34 Saya rasa saya menyakiti hati mereka yang rapat dengan saya m37 35 Saya merasa risau tentang kesan sampingan rawatan saya m38 36 Saya boleh berkongsi dengan orang lain tentang kesukaran yang saya alami disebabkan penyakit sendi (arthritis) sebanyak mana yang saya suka sp39 37 Saya merasakan orang lain faham tentang kesusahan yang saya alami disebabkan penyakit sendi (arthritis) saya sp40 38 Saya merasa malu untuk meminta bantuan/pertolongan jika perlu m41 39 Saya rasa saya diberi sokongan oleh orang yang rapat dengan saya (pasangan dan keluarga) sp42 40 Saya rasa saya diberi sokongan oleh orang yang berada di sekeliling saya (kawan dan jiran) sp43 Py: physical activity; m: mental; pn: pain; sf: social functioning; sp: social support.Table 8
Prevalidation of English version of OAKHQOL questionnaire (40 items).
Domain 1 I have difficulty walking py1 2 I have difficulty bending down or straightening up py2 3 I have difficulty carrying heavy things py3 4 I have difficulty going down stairs py4 5 I have difficulty climbing stairs py5 6 I have difficulty taking a bath py6 7 I have difficulty getting dressed py7 8 I have difficulty cutting my toe-nails py8 9 I have difficulty getting going again after staying in the same position for a long time py9 10 I have difficulty getting in and out of a car py10 11 I have difficulty using public transport py11 12 I have to pace myself py13 13 I take more time to do things py14 14 My spirits are low because of the pain m15 15 I worry about being dependent on others m16 16 I worry about being disabled m17 17 I feel embarrassed when people look at me m18 18 I am anxious m19 19 I am depressed m20 20 I feel my family life is being affected m21 21 I have difficulty staying in the same position for a long time py24 22 I need a walking stick/cane or crutches to walk py25 23 I have pain (describe frequency) pn26 24 I have pain (describe intensity) pn27 25 I need help for things like housework and shopping py28 26 I feel older than my age m29 27 I am able to plan projects for the long term sf30 28 I get out of the house as much as I like sf31 29 I entertain at home as much as I like sf32 30 I have difficulty getting to sleep or getting back to sleep because of pain pn33 31 I wake up because of pain pn34 32 I wonder what will become of me m35 33 I am irritable or aggressive m36 34 I feel I annoy those close to me m37 35 I am worried about the side effects of my treatment m38 36 I can talk to others about the difficulties I have due to my arthritis as much as I like sp39 37 I feel others understand the difficulties I have because of my arthritis sp40 38 I am embarrassed to ask for help if I need it m41 39 I feel supported by people close to me sp42 40 I feel supported by those around me sp43 Py: physical activity; m: mental; pn: pain; sf: social functioning; sp: social support.


## 4. Discussion

Recently, validated health-related quality of life that accurately reflects a patient’s experience with respect to specific disease has been an important outcome recommended for interventional study. Health-related quality of life is a broad concept representing individual responses to physical, mental, and social effects on daily living. Therefore, the need to assess conceptual relevance and psychometric properties in various cultures or countries is increasing [15].The present study indicated that the shortened Malay version of the OAKHQOL had good validity and reliability and is culturally acceptable. EFA of the original OAKHQOL using principle component analysis with orthogonal varimax rotation revealed four factors: physical activities, mental health, social support, and social functioning with the pain factor as an individual dimension [10, 15]. The OAKHQOL has also been validated in Spanish and Persian [2, 29]. However, to our knowledge, this is the first study that used confirmatory analysis in the validation analysis. CFA is used to verify the factor structure of a measurement instrument. CFA has become more commonly used for construct validation and to provide evidence for convergent and discriminant validity of the theoretical construct [30]. Furthermore, CFA is a theory-testing model and it starts with a hypothesis prior to the analysis which is based on strong theoretical and/or empirical foundation [31]. On the other hand, EFA is used to explore the possible underlying factor structure of a measurement instrument [32].The panel in this study decided to keep the original five-factor model in the initial analysis, although the EFA of the original study did not support this. EFA of the original study was done in other language; thus the result was different. The decision to keep the pain construct in the final model was made because we found the pain factor to be an important domain that is also available in and consistent with other health-related QOL for OA measures and the items were also culturally acceptable [16, 17].We made the decision to remove six items from the physical activity construct (py3, py9, py13, py14, py24, and py25), five items in the mental health construct (m16, m29, m36, m37, and m38), and one item in the social support construct (sp39) because other items in the construct reflected similar functions. Most of the items were removed because of significant overlapping (high modification indices) and lack of discrimination within the items. Removal of these items was shown to improve the fit indices of the model, indicating that perhaps they poorly represented the construct being measured. However, the panel of this study had also revisited and reviewed the items before they were removed because they might represent important and meaningful construct as mentioned in a previous validation study.The reliability analysis showed that internal consistency of the Malay version OAKHQOL was acceptable. Other than that, the CR and AVE for each construct were also acceptable, indicating that they had good levels of internal consistency. As for the criterion validity, the analysis showed that the physical and pain constructs of the Malay version of OAKHQOL had good correlations with the functional and pain constructs of the WOMAC. In Malay version of OAKHQOL, physical activity construct has 10 items whereas WOMAC has 17 items in functional construct [16]. In physical activity and functional construct of both questionnaires, daily activities such as difficulty in walking, bending, going up and down the stairs, and getting in and out of a car or a bus were assessed. Physical activity on self-care such as taking bath, getting dressed, and cutting toe-nails was assessed in OAKHQOL, whereas WOMAC assessed other aspects of daily activities such as difficulty in sitting, standing, lying on bed, getting up from sitting or from bed, shopping, and also doing house chores [16]. Perhaps future research can examine the criterion validity for the mental construct, social functioning, and social support of the Malay version of OAKHQOL. The SF36 is one questionnaire that has been used to assess health-related QOL for people with knee OA, although it is not disease-specific. This questionnaire has been validated in the Malay language. We suggest correlating the OAKHQOL scores with the SF36 in a future study.For the known group validity, we found that the Malay version of OAKHQOL discriminates well for the BMI groups and the severity of disease based on plain radiograph for the physical activity, pain, and mental domains. However, for the social domains, it was not discriminative based on disease severity. This finding was similar to the findings of De Tejada et al., who conducted the validation study in Spanish [2]. Both Malay and English versions after validation are shown in Tables 9 and 10.Table 9
Postvalidation of English version of OAKHQOL questionnaire (28 items).
Domain 1 I have difficulty walking py1 2 I have difficulty bending down or straightening up py2 3 I have difficulty going down stairs py4 4 I have difficulty climbing stairs py5 5 I have difficulty taking a bath py6 6 I have difficulty getting dressed py7 7 I have difficulty cutting my toe-nails py8 8 I have difficulty getting in and out of a car py10 9 I have difficulty using public transport py11 10 My spirits are low because of the pain m15 11 I worry about being disabled m17 12 I feel embarrassed when people look at me m18 13 I am anxious m19 14 I am depressed m20 15 I feel my family life is being affected m21 16 I have pain (describe frequency) pn26 17 I have pain (describe intensity) pn27 18 I need help for things like housework and shopping py28 19 I am able to plan projects for the long term sf30 20 I get out of the house as much as I like sf31 21 I entertain at home as much as I like sf32 22 I have difficulty getting to sleep or getting back to sleep because of pain pn33 23 I wake up because of pain pn34 24 I wonder what will become of me m35 25 I feel others understand the difficulties I have because of my arthritis sp40 26 I am embarrassed to ask for help if I need it m41 27 I feel supported by people close to me sp42 28 I feel supported by those around me sp43 Py: physical activity; m: mental; pn: pain; sf: social functioning; sp: social support.Table 10
Postvalidation of Malay version of OAKHQOL questionnaire (28 items).
Domain 1 Saya mengalami kesusahan untuk berjalan py1 2 Saya mengalami kesusahan untuk tunduk atau meluruskan badan/bangun semula py2 3 Saya mengalami kesusahan untuk menuruni tangga py4 4 Saya mengalami kesusahan untuk menaiki tangga py5 5 Saya mengalami kesusahan untuk mandi py6 6 Saya mengalami kesusahan untuk berpakaian lengkap (seperti memakai stoking, kasut, seluar dan sebagainya) py7 7 Saya mengalami kesusahan untuk memotong kuku kaki py8 8 Saya mengalami kesusahan untuk masuk dan keluar daripada kereta py10 9 Saya mengalami kesusahan untuk menggunakan kenderaan awam (bas, teksi dsb) py11 10 Saya kurang bersemangat disebabkan sakit m15 11 Saya risau menjadi tidak berkemampuan m17 12 Saya merasa malu apabila orang melihat saya m18 13 Saya berasa gelisah m19 14 Saya berasa tertekan m20 15 Saya merasakan kehidupan keluarga saya terjejas m21 16 Saya mengalami kesakitan (kekerapan) pn26 17 Saya mengalami kesakitan (keterukan) pn27 18 Saya memerlukan pertolongan untuk membuat sesuatu seperti kerja rumah dan membeli belah py28 19 Saya mampu/boleh merancang projek/program untuk jangkamasa yang panjang sf30 20 Saya keluar rumah sekerap mana yang saya suka sf31 21 Saya melayan tetamu di rumah sebanyak mana yang saya suka sf32 22 Saya mengalami kesukaran untuk tidur atau tidur semula kerana sakit pn33 23 Saya terjaga disebabkan sakit pn34 24 Saya tertanya-tanya apa yang bakal berlaku/kan terjadi kepada saya m35 25 Saya merasakan orang lain faham tentang kesusahan yang saya alami disebabkan penyakit sendi (arthritis) saya sp40 26 Saya merasa malu untuk meminta bantuan/pertolongan jika perlu m41 27 Saya rasa saya diberi sokongan oleh orang yang rapat dengan saya (pasangan dan keluarga) sp42 28 Saya rasa saya diberi sokongan oleh orang yang berada di sekeliling saya (kawan dan jiran) sp43 Py: physical activity; m: mental; pn: pain; sf: social functioning; sp: social support.This study is not without limitation. First, this study involved only people with knee OA; therefore, the findings may not be generalized to patients with hip OA. In addition, the convenient sampling was applied. Thus, it may not represent the true knee OA population in the community. It is also good to measure the responsiveness of this questionnaire in a clinical trial where it can be used to evaluate changes in patient status following therapeutic intervention.


## 5. Conclusion

The Malay version of OAKHQOL consisting of five factors assessed through 28 items was valid, reliable, and acceptable to measure quality of life in Malaysian population with knee OA.



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*Source: 4329751-2018-05-31.xml*