|Year : 2018 | Volume
| Issue : 1 | Page : 8-15
Reliability and validity of modified western ontario and mcmaster universities osteoarthritis index gujarati version in participants with knee osteoarthritis
Ratan P Khuman1, Dhara Chavda2, Lourembam Surbala1, Urmi Bhatt2
1 Department of Musculoskeletal Physiotherapy and Neurophysiotherapy, Ashok & Rita Patel Institute of Physiotherapy, Anand, Gujarat, India
2 Department of Musculoskeletal Physiotherapy, C. U. Shah Physiotherapy College, Surendranagar, Gujarat, India
|Date of Submission||21-Aug-2017|
|Date of Acceptance||22-Dec-2017|
|Date of Web Publication||19-Jun-2018|
Dr. Ratan P Khuman
Ashok & Rita Patel Institute of Physiotherapy, CHARUSAT, Anand - 388 421, Gujarat
Source of Support: None, Conflict of Interest: None
BACKGROUND: Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) is the most widely used condition-specific self-reported multidimensional instrument for the assessment of hip or knee osteoarthritis (OA).
OBJECTIVE: The objective of this study is to translate and to investigate the reliability and validity of modified WOMAC (mWOMAC) Gujarati version in participants with knee OA.
MATERIALS AND METHODOLOGY: The Indian version mWOMAC English questionnaire was translated into Gujarati with forward and backward method, and its psychometric properties were analyzed on 230 Gujarati-speaking participants with knee OA (mean age = 58.4 years). The visual analog scale (VAS) for pain and handheld dynamometer (HHD) for isometric quadriceps strength along with mWOMAC was recorded twice within 2 days, and data were used to assess the reliability and convergent validity.
RESULTS: The mWOMAC Gujarati version questionnaire was internally consistent with Cronbach's alpha 0.936 (test), 0.940 (retest), respectively. Test-retest reliability was analyzed using mixed model intraclass correlation coefficient (ICC) and found satisfactory with ICCs of 0.986. Convergent validity was analyzed using Pearson's correlation coefficient between mWOMAC and VAS (P < 0.05, r = 0.716); mWOMAC and HHD (P < 0.05; r = −0.915) and significant correlation was found.
CONCLUSION: The mWOMAC Gujarati version is a reliable and valid self-rated clinical instrument for the assessment of symptoms and function in OA knee.
Keywords: Handheld dynamometer, knee osteoarthritis, modified Western Ontario and McMaster Universities Osteoarthritis Index Gujarati version, reliability, validity, visual analog scale
|How to cite this article:|
Khuman RP, Chavda D, Surbala L, Bhatt U. Reliability and validity of modified western ontario and mcmaster universities osteoarthritis index gujarati version in participants with knee osteoarthritis. Physiother - J Indian Assoc Physiother 2018;12:8-15
|How to cite this URL:|
Khuman RP, Chavda D, Surbala L, Bhatt U. Reliability and validity of modified western ontario and mcmaster universities osteoarthritis index gujarati version in participants with knee osteoarthritis. Physiother - J Indian Assoc Physiother [serial online] 2018 [cited 2018 Nov 16];12:8-15. Available from: http://www.pjiap.org/text.asp?2018/12/1/8/229112
| Introduction|| |
According to the American College of Rheumatology, osteoarthritis (OA) is “a group of conditions that lead to joint signs and symptoms which are associated with the defective integrity of articular cartilage in addition to, related changes in the underlying bone and articular margins.” Knee OA is divided into two groups either idiopathic (primary) or secondary. Idiopathic knee OA is classified by clinical, clinical, and laboratory and/or clinical and radiological criteria.
Multifactorial etiology of OA (including various predisposing factors) leads to changes at morphological, biochemical, and other levels in individuals. Clinical characteristics of knee OA primarily include pain, stiffness, and loss of movement or function with other features such as joint swelling, crepitation, soft-tissue contractures, and muscle weakness., Knee OA affects an individual's body structure, functions, activity, and participation as per the WHO classification International Classification of Functioning (ICF), hence, affecting the quality of life. The prevalence of knee OA is increasing worldwide in the last few decades. Various studies state the global age-matched prevalence of knee OA to be 3.8% and pooled prevalence of knee OA to be 7.9%., Whereas, in India, it is 13% and 8.1% in rural and urban population, respectively. Knee OA along with hip OA is also the 11th most common contributing factor to global disability  that places a significant burden on the health-care system.
Numerous patient-based subjective instruments have been developed to quantify the health status of patients with knee OA in the recent decade. Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) is the most widely used multidimensional self-reported questionnaire with well-known psychometric properties for patients with hip and knee OA. It consists of three domains: five questions for pain, two questions for stiffness, and seventeen questions for functional activities. WOMAC has been translated, validated, and modified in numerous version to match cross-cultural variations since its presentation by Bellamy et al. in 1986.,, Modified WOMAC (mWOMAC) (also known as Pune version of modified Stanford WOMAC) was adapted and validated from original WOMAC for Indian population to suit cultural modifications and claimed to be translated in different regional languages., To the best of our knowledge and through extensive literature search, the validity and reliability study for mWOMAC Gujarati version have not yet been conducted in Gujarati-speaking participants with knee OA. Hence, the aim of this study was to translate mWOMAC into Gujarati language, analyze its linguistic reliability and validity and to present data in metric properties. We hypothesized that mWOMAC Gujarati version would be reliable and valid clinical instrument for the assessment of symptoms and physical function in OA knee.
| Materials and Methodology|| |
In this cross-sectional study, 312 individuals [Figure 1] who came for the treatment of OA knee to institutional-based musculoskeletal outpatient physiotherapy department were screened to participate in the study. The physical examination was not a part of screening as the participants were already receiving treatment. For inclusion in the study, participants should have knee OA (tibiofemoral/patellofemoral/both, primary/secondary) as the only source of pain or disability in the lower extremity, age above 35 years, both genders, no previous surgery for knee OA and should be able to read and understand Gujarati. They were excluded if associated with concurrent systemic inflammatory rheumatic disease, medical comorbidities that would disturb participation, neurological disorders affecting lower extremity, psychiatric disorders, visual or hearing impairments, and planned knee arthroplasty within 1 week. In all the included participants, Gujarati was the mother tongue. The institutional scientific committee reviewed and approved this study. We explained all the participants about the study procedure and took their informed consent.
Process of translation and adaptation of instruments
The translation of mWOMAC in Gujarati format was done as per the WHO guidelines of translation and adaptation of the instrument.
Two bilingual health-care professional researchers who were aware of the objectives of the questionnaire did the forward translation. Both the translators had the knowledge of the English-speaking culture, whose native language is Gujarati and fluent in English. Both the translators were instructed to emphasize on conceptual rather than literal translations, avoid any medical terms or jargons, and keep it simple and easy to understand.
A bilingual expert panel consisting of five health-care professional researchers, including the original translator, reviewed the translated version to identify and resolve the inadequate expressions or concepts. The panel also reviewed for any discrepancies between the forward translations with the existing version of the questions. After implicating the suggestions from the expert panel, a translated Gujarati version of the questionnaire was ready for backward translation.
Using the same approach as step one, two bilingual nonhealth-care professionals who had no prior knowledge of the tool performed the backward translation of the Gujarati version questionnaire to English. Then, a group discussion evaluated the similarities and dissimilarities of translations with the English mWOMAC questionnaire. No significant differences were found between English mWOMAC and translated mWOMAC Gujarati questionnaire.
A pretesting of the questionnaire was performed on 15 samples (8 females and 7 males) aged 45 years and above and belonging to different sociodemographics. The participants were asked to express their understanding of each question or any difficulty faced in understanding the questions. The participants reported none and hence we approved the final questionnaire for the study.
Western Ontario and McMaster Universities Osteoarthritis Index
The WOMAC is a self-report disease-specific multidimensional questionnaire assessing pain (5 questions), stiffness (2 questions), and physical functional disability (17 questions) of hip and knee OA. Since its development in 1986, the index is widely used and popularized among the researchers globally in studies of OA of hip or knee joint. Reporting of symptoms in original WOMAC can be made using either of 5-point-Likert type scale or of visual analog scale (VAS) (10 cm/100 mm)., To meet the demands of various populations worldwide, scale has been modified and analyzed by numerous researchers.,,,,,,,,,,,,, In this current study, mWOMAC (5-point-Likert type scale) developed by the Center for Rheumatic Diseases, Pune, that has been modified to adapt with Indian culture  was used to translate into the Gujarati language [Table 1]. The subscale of pain carries 20 points, stiffness 8 points, and physical functional disability 68 points where 96 points represent an overall score of WOMAC, which indicates the worst possible score. Each of the 24 questions was rated 0–4 Likert scale where “0” represents “none” and “4” representing “extreme.” The participants were handed a copy of the mWOMAC Gujarati version questionnaire [Table 1] and were asked to fill up the same in the department during their visits.
|Table 1: Twenty-for items Modified Western Ontario and McMaster Universities Osteoarthritis Index English and Gujarati Version|
Click here to view
Visual analog scale
VAS is a widely used unidimensional tool for clinical assessment of adult pain intensity. VAS has been studied and proven a reliable and valid measure of chronic pain intensity.,, In this study, we have used a 10 cm horizontal line  marking from score “0” representing “no pain” and score “10” representing “worst imaginable pain” for recording pain related to OA knee. The participants were instructed to mark a point on the 10 cm line, which represents their knee pain, and the obtained values were used for comparative analysis. They were also instructed to avoid marking preferred number, value, or any other verbal descriptions.,
Handheld dynamometer (HHD) is a portable and relatively inexpensive device which can be a practical alternative to isokinetic dynamometry for muscle strength assessment. Higher the score (pound or kilogram) indicates the greater isometric strength of the testing muscles and vice versa. Reliability of HHD in the assessment of quadriceps strength has been tested and proven in various population.,,,, The HHD is a reliable tool for isometric muscle strength testing and recommended being an integral part of the routine clinical assessment of musculoskeletal conditions around hip and knee joints. The testing procedure was adopted as described by the previous study, which has been tested in elderly OA patients. Volunteers were asked to perform three trials, and the best performance was recorded in pounds which was used for the comparative analysis.
Demographic data collection [Table 2], recording of pain (VAS), isometric quadriceps strength (HHD), and mWOMAC Gujarati version was made on the first visit, and measurements were repeated within the next 2 days. A single researcher recorded the HHD values for isometric quadriceps strength for all the participants on all occasions who was unaware of VAS and mWOMAC Gujarati version scores.
A total 230 participants completed the test and retest of mWOMAC Gujarati version along with pain assessment using VAS and isometric quadriceps strength evaluation using HHD. All statistical analysis of the obtained data was performed using IBM SPSS Statistics 22 version (Armonk, NY: IBM Corp). Demographic data (age, height, weight, body mass index (BMI), and duration of the condition) were descriptively analyzed to calculate mean and standard deviation (SD) and other demographic data (gender, Kellgren-Lawrence grading score, affected side, affected joint, type of OA, and deformity) were analyzed for frequencies. Normality and uniformity of data were verified with Kolmogorov–Smirnov Test which was always present, and therefore, parametric tests were adapted to estimate statistical values.
Internal consistency of the mWOMAC Gujarati version was determined using Cronbach's alpha to estimate correlations between the items of mWOMAC Gujarati version. The alpha value of 0.7 was regarded as acceptable (Steiner and Norman, 2008). Test-retest reliability of the mWOMAC Gujarati version was analyzed using mixed model intraclass correlation (ICC) coefficients at 95% confidence interval (CI). Values of ICC thus vary from 1 (perfect correlation) to 0 (no correlation).
Criterion validity in terms of convergence between VAS (which measured pain) and HHD (which measured isometric quadriceps strength) was examined. Correlations were made between measures using Pearson's correlation coefficients method at 95% CI.
| Results|| |
[Table 2] shows the demographic characteristics (age, gender, height, weight, BMI, duration of condition, Kellgren–Lawrence rating score, affected side, affected joint, type of OA, and deformity) of the participants. Mean age of participants was 58.73 ± 9.82. Out of 230 participants, 117 (50.9%) were female; mean BMI 27.34 ± 5.00 and mean duration (months) of knee OA were 16.28 ± 13.25. Among the different grades of knee OA, 48.3% were Grade-2, 23.9% were Grade-3, 22.6% were Grade-1, and 5.2% were Grade-4.
Reliability (internal consistency)
We assessed the internal consistency of mWOMAC Gujarati version with inter-item correlation after translation. Averaged Cronbach's alpha of inter-item correlation was 0.936 for test and 0.940 for retest, which suggests an excellent inter-item correlation of the mWOMAC Gujarati version to act as a reliable and an internally consistent tool. [Table 3] demonstrates the further details of the alpha test.
|Table 3: Inter-item analysis to test the internal consistency of Modified Western Ontario and McMaster Universities Osteoarthritis Index Gujarati version using Cronbach's alpha (α)|
Click here to view
Reliability (test-retest reliability)
To check the repeatability of mWOMAC Gujarati version, we carried out inter-class coefficient (ICC). Averaged measure ICC of the mWOMAC Gujarati version was 0.986, suggesting excellent test-retest reliability. Furthermore, also obtained ICC for HHD and VAS with an average value of 0.977 and 0.854, respectively, suggesting VAS as a reliable tool for pain measurement and HHD for isometric strength testing of the quadriceps muscle in OA knee participants. [Table 4] demonstrated the further details of ICC testing of mWOMAC, VAS, and HHD.
|Table 4: Test-retest reliability testing with intraclass correlation coefficient|
Click here to view
Validity (convergent validity)
We checked the convergent validity using Pearson's correlation test to find the relationship among mWOMAC Gujarati Version, VAS, and HHD. As shown in [Table 5], there were significant correlations among the scores of mWOMAC Gujarati version, VAS, and HHD. However, the strength of correlations among the measures was not symmetrical.
The correlation between mWOMAC Gujarati version and HHD revealed a stronger correlation (r = (-)0.915, P < 0.05) than that of mWOMAC Gujarati Version and VAS (r = 0.716, P < 0.05).
| Discussion|| |
The prevalence of OA increases with age, which is associated with a decrease in physiological function and leads to major health consequences., In both clinical research and clinical practice, evaluation of the therapeutic benefits of interventions are of key importance. WOMAC and mWOMAC are established self-reported outcome measures of health status in subjects with hip or knee OA.,,,,, Reliability, validity, and responsiveness are essential attributes of health status measurement tools. Various lingual translations of mWOMAC are validated and tested for reliability to promote the effectiveness of interventions in OA knee population., In the present study, we report on the linguistic reliability and validation of Gujarati version mWOMAC and present data in metric properties.
Reliability concerns the degree to which results of measurements are consistent across repeated measurements. In the current study, the reliability of Gujarati version mWOMAC was evaluated in terms of internal consistency and test-retest reliability yielding excellent reliability values. Internal consistency of mWOMAC was found to be excellent (Cronbach's alpha >0.9) with excellent test-retest reliability (ICC > 0.9). A significantly strong correlation was found between the Gujarati version of mWOMAC and isometric quadriceps strength (r > 0.9, P < 0.05) and pain (r > 0.7, P < 0.05). These findings of our present study are similar to those of other translated versions, as well as the original WOMAC.,,,,,,,,,,,,,,,
Construct validity is concerned with the degree that a particular measurement confirms to predicted correlation with other theoretical propositions or measures. As OA knee has been found to be a major public health problem in elderly population and major cause of disability,, much of research work has been carried out to conclude the determinants of disability in OA knee. Many variables including quadriceps strength, pain, age, duration of symptoms, radiological grading, and types of deformities have been analyzed for their association with disability and progression of disease in OA knee. Among these variables, quadriceps strength and knee pain have been found to be an important and consistent determinants of functional impairments in OA knee population.,, In the present study, construct validity was examined in terms of the convergence between similar dimensions of the self-reported Gujarati version mWOMAC, isometric quadriceps strength, and pain.
The lower limb muscle strength decreases with age, the decline generally beginning in the fifth decade.,, As shown by O'Reilly et al., a strong association lies between quadriceps strength with knee pain and disability in the community. Several other cross-sectional studies have highlighted the association between reduced knee extensor strength in people with OA knee with increased pain and poor physical function.,, Hence, considering isometric quadriceps strengths as a good reflector of physical function and pain in OA knee population, we examined the convergence between the Gujarati version of mWOMAC and isometric quadriceps strength as measured by handheld dynamometer. A strong negative correlation between the two measures (r< (-)0.9, P < 0.05) has been found in the present study, which is in accordance with other researchers.,, It indicates that the Gujarati version of mWOMAC is a valid measure of OA knee symptoms and physical function assessment.
Knee pain is one of the major concerns seeking treatment, which is also an important determinant of severity and disability in OA knee., Knee pain has an adverse effect on quadriceps strength, proprioception, and physical function., Thus, considering pain as the core component in OA knee that can have an effect on all dimensions, we examined the convergence between the Gujarati version of mWOMAC and pain, as measured by VAS. The results of correlation are in accordance with the previous studies ,,,,,, and a strong correlation (r > 0.7, P < 0.05) has been found between two measures that conclude Gujarati version of mWOMAC to be a valid measure of OA knee symptoms and function.
The findings of this study will be of help in the future researchers that target Gujarati population with OA knee. This study proves the reliability and validity of the Gujarati version of mWOMAC; yet, further research is recommended to study the responsiveness of the Gujarati version of mWOMAC.
| Conclusion|| |
The results reported in this study shows the reliability and validity of self-reported Gujarati version of mWOMAC for assessing the consequences of OA knee among Gujarati-speaking OA knee participants and its psychometric properties are in agreement with the widely used original version. In addition, none of the participants reported difficulty or any objection in completing the mWOMAC questionnaire.
We are thankful to all the valuable volunteers of this study for their cooperation during the study. We would like to extend our sincere thanks to Mrs. Anjana Chavda (M.A., M. Phil) for helping in translation of mWOMAC into Gujarati dialect. We extend our hearty thanks to C.U. Shah Physiotherapy College management team for allowing and boosting us to conduct the research work.
Financial support and sponsorship
Equipment Support for this study was provided by C. U. Shah Physiotherapy College.
Conflicts of interest
There are no conflicts of interest.
| References|| |
Altman R, Alarcón G, Appelrouth D, Bloch D, Borenstein D, Brandt K, et al
. The American College of Rheumatology criteria for the classification and reporting of osteoarthritis of the knee. Arthritis Rheum 1991;34:505-14.
Firestein GS, Budd RC, Harris ED Jr., McInnes IB, Ruddy S, Sergeant JS. Kelley's Textbook of Rheumatology. 8th
ed. Canada: Sunders Elsevier; 2008.
Arden N, Blanco F, Cooper C, Guermazi A, Hayashi D, Hunter D. Atlas of Osteoarthritis, UK: Springer Healthcare; 2014.
Cross M, Smith E, Hoy D, Nolte S, Ackerman I, Fransen M, et al.
The global burden of hip and knee osteoarthritis: Estimates from the global burden of disease 2010 study. Ann Rheum Dis 2014;73:1323-30.
Haq SA, Davatchi F. Osteoarthritis of the knees in the COPCORD world. Int J Rheum Dis 2011;14:122-9.
Sharma R, editor. Epidemiology of Musculoskeletal Conditions in India. New Delhi, India: Indian Council of Medical Research (ICMR); 2012.
Bellamy N, Buchanan WW, Goldsmith CH, Campbell J, Stitt LW. Validation study of WOMAC: A health status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug therapy in patients with osteoarthritis of the hip or knee. J Rheumatol 1988;15:1833-40.
Bellamy N, Buchanan WW, Goldmith CH, Campbell J, Stitt L. Validation study of WOMAC: A health status instrument for measuring clinically-important patient relevant outcomes following total hip or knee arthroplasty in osteoarthritis. J Orthop Rheumatol 1988;1:95-108.
McConnell S, Kolopack P, Davis AM. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC): A review of its utility and measurement properties. Arthritis Care Res 2001;45:453-61.
Chopra A, Lavin P, Patwardhan B, Chitre D. A 32-week randomized, placebo-controlled clinical evaluation of RA-11, an ayurvedic drug, on osteoarthritis of the knees. J Clin Rheumatol 2004;10:236-45.
Salaffi F, Leardini G, Canesi B, Mannoni A, Fioravanti A, Caporali R, et al.
Reliability and validity of the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index in Italian patients with osteoarthritis of the knee. Osteoarthritis Cartilage 2003;11:551-60.
Roorda LD, Jones CA, Waltz M, Lankhorst GJ, Bouter LM, van der Eijken JW, et al.
Satisfactory cross cultural equivalence of the Dutch WOMAC in patients with hip osteoarthritis waiting for arthroplasty. Ann Rheum Dis 2004;63:36-42.
Nadrian H, Moghimi N, Nadrian E, Moradzadeh R, Bahmanpour K, Iranpour A, et al.
Validity and reliability of the Persian versions of WOMAC osteoarthritis index and lequesne algofunctional index. Clin Rheumatol 2012;31:1097-102.
Faucher M, Poiraudeau S, Lefevre-Colau MM, Rannou F, Fermanian J, Revel M, et al.
Assessment of the test-retest reliability and construct validity of a modified WOMAC index in knee osteoarthritis. Joint Bone Spine 2004;71:121-7.
Stucki G, Meier D, Stucki S, Michel BA, Tyndall AG, Dick W, et al.
Evaluation of a German version of WOMAC (Western Ontario and McMaster universities) arthrosis index. Z Rheumatol 1996;55:40-9.
Roos EM, Klässbo M, Lohmander LS. WOMAC osteoarthritis index. Reliability, validity, and responsiveness in patients with arthroscopically assessed osteoarthritis. Western Ontario and McMaster universities. Scand J Rheumatol 1999;28:210-5.
Wigler I, Neumann L, Yaron M. Validation study of a Hebrew version of WOMAC in patients with osteoarthritis of the knee. Clin Rheumatol 1999;18:402-5.
Thumboo J, Chew LH, Soh CH. Validation of the western Ontario and McMaster university osteoarthritis index in Asians with osteoarthritis in Singapore. Osteoarthritis Cartilage 2001;9:440-6.
Bae SC, Lee HS, Yun HR, Kim TH, Yoo DH, Kim SY, et al.
Cross-cultural adaptation and validation of Korean western Ontario and McMaster universities (WOMAC) and lequesne osteoarthritis indices for clinical research. Osteoarthritis Cartilage 2001;9:746-50.
Escobar A, Quintana JM, Bilbao A, Azkárate J, Güenaga JI. Validation of the Spanish version of the WOMAC questionnaire for patients with hip or knee osteoarthritis. Western Ontario and McMaster universities osteoarthritis index. Clin Rheumatol 2002;21:466-71.
Guermazi M, Poiraudeau S, Yahia M, Mezganni M, Fermanian J, Habib Elleuch M, et al.
Translation, adaptation and validation of the western Ontario and McMaster universities osteoarthritis index (WOMAC) for an Arab population: The Sfax modified WOMAC. Osteoarthritis Cartilage 2004;12:459-68.
Tüzün EH, Eker L, Aytar A, Daşkapan A, Bayramoğlu M. Acceptability, reliability, validity and responsiveness of the Turkish version of WOMAC osteoarthritis index. Osteoarthritis Cartilage 2005;13:28-33.
Scott J, Huskisson EC. Vertical or horizontal visual analogue scales. Ann Rheum Dis 1979;38:560.
McCormack HM, Horne DJ, Sheather S. Clinical applications of visual analogue scales: A critical review. Psychol Med 1988;18:1007-19.
Gaston-Johansson F. Measurement of pain: The psychometric properties of the pain-O-meter, a simple, inexpensive pain assessment tool that could change health care practices. J Pain Symptom Manage 1996;12:172-81.
Huskisson EC, Wojtulewski JA, Berry H, Scott J, Hart FD, Balme HW, et al.
Treatment of rheumatoid arthritis with fenoprofen: Comparison with aspirin. Br Med J 1974;1:176-80.
Scott J, Huskisson EC. Graphic representation of pain. Pain 1976;2:175-84.
Koblbauer IF, Lambrecht Y, van der Hulst ML, Neeter C, Engelbert RH, Poolman RW, et al.
Reliability of maximal isometric knee strength testing with modified hand-held dynamometry in patients awaiting total knee arthroplasty: Useful in research and individual patient settings? A reliability study. BMC Musculoskelet Disord 2011;12:249.
Oldham JA, Howe TE. Reliability of isometric quadriceps muscle strength testing in young subjects and elderly osteoarthritic subjects. Physiotherapy 1995;81:399-404.
Kelln BM, McKeon PO, Gontkof LM, Hertel J. Hand-held dynamometry: Reliability of lower extremity muscle testing in healthy, physically active, young adults. J Sport Rehabil 2008;17:160-70.
Katz-Leurer M, Rottem H, Meyer S. Hand-held dynamometry in children with traumatic brain injury: Within-session reliability. Pediatr Phys Ther 2008;20:259-63.
Mercer VS, Lewis CL. Hip abductor and knee extensor muscle strength of children with and without Down syndrome. Pediatr Phys Ther 2001;13:18-26.
Martin HJ, Yule V, Syddall HE, Dennison EM, Cooper C, Aihie Sayer A. Is handheld dynamometry useful for the measurement of quadriceps strength in older people? A comparison with the gold standard Bodex dynamometry. Gerontology 2006;52:154-9.
Maffiuletti NA. Assessment of hip and knee muscle function in orthopaedic practice and research. J Bone Joint Surg Am 2010;92:220-9.
O'Reilly SC, Jones A, Muir KR, Doherty M. Quadriceps weakness in knee osteoarthritis: The effect on pain and disability. Ann Rheum Dis 1998;57:588-94.
Hamerman D. Clinical implications of osteoarthritis and ageing. Ann Rheum Dis 1995;54:82-5.
WOMAC Osteoarthritis Index. WOMAC ®
3.1 Index Knee and Hip Osteoarthritis Index; 03 August, 2017. Available from: http://www.womac.org/womac/
. [Last updated on 2017 Aug 03].
Bellamy N. The WOMAC knee and hip osteoarthritis indices: Development, validation, globalization and influence on the development of the AUSCAN hand osteoarthritis indices. Clin Exp Rheumatol 2005;23:S148-53.
Turk DC, Dworkin RH, Allen RR, Bellamy N, Brandenburg N, Carr DB, et al.
Core outcome domains for chronic pain clinical trials: IMMPACT recommendations. Pain 2003;106:337-45.
Carmines EG, Zeller RA. Reliability and Validity Assessment. Beverly Hills: Sage Publications; 1979.
Hassan BS, Doherty SA, Mockett S, Doherty M. Effect of pain reduction on postural sway, proprioception, and quadriceps strength in subjects with knee osteoarthritis. Ann Rheum Dis 2002;61:422-8.
McAlindon TE, Cooper C, Kirwan JR, Dieppe PA. Determinants of disability in OA knee. Ann Rheum Dis 1993;52: 258-62.
Sharma L, Cahue S, Song J, Hayes K, Pai YC, Dunlop D, et al.
Physical functioning over three years in knee osteoarthritis: Role of psychosocial, local mechanical, and neuromuscular factors. Arthritis Rheum 2003;48:3359-70.
Skelton DA, Greig CA, Davies JM, Young A. Strength, power and related functional ability of healthy people aged 65-89 years. Age Ageing 1994;23:371-7.
Murray MP, Duthie EH Jr., Gambert SR, Sepic SB, Mollinger LA. Age-related differences in knee muscle strength in normal women. J Gerontol 1985;40:275-80.
Murray MP, Gardner GM, Mollinger LA, Sepic SB. Strength of isometric and isokinetic contractions: Knee muscles of men aged 20 to 86. Phys Ther 1980;60:412-9.
Fransen M, Crosbie J, Edmonds J. Isometric muscle force measurement for clinicians treating patients with osteoarthritis of the knee. Arthritis Rheum 2003;49:29-35.
Slemenda C, Brandt KD, Heilman DK, Mazzuca S, Braunstein EM, Katz BP, et al.
Quadriceps weakness and osteoarthritis of the knee. Ann Intern Med 1997;127:97-104.
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]