Validation of the Spanish Version of the WOMAC Questionnaire for Patients with Hip or Knee Osteoarthritis

1. Clin Rheumatol (2002) 21:466–471
ß 2002 Clinical Rheumatology
Clinical
Rheumatology
Original Article
Validation of the Spanish Version of the WOMAC Questionnaire for
Patients with Hip or Knee Osteoarthritis
A. Escobar1, J. M. Quintana2, A. Bilbao2, J. Azkarate3 and J. I. Guenaga4
´ ¨
1
Hospital of Basurto, Bilbao; 2Hospital of Galdakao, Vizcaya; 3Hospital of Mendaro, Mendaro; and 4Hospital of Santiago, Vitoria-
Gasteiz, Spain
Abstract: The aim of this study was to validate a OA ranged from 0.8 to 1.5. The Spanish version of
translated version of the Western Ontario and McMaster WOMAC is a valid, reliable and responsive instrument
Universities Osteoarthritis Index (WOMAC) question- in patients with hip or knee OA.
naire in Spanish patients with hip or knee osteoarthritis
(OA). The WOMAC questionnaire and the SF-36 were Keywords: Hip replacement; Knee replacement; Osteo-
administered to a sample of 269 patients on the waiting arthritis; Quality of life; WOMAC validation
list for hip or knee replacement. We studied the
convergent validity and the item-scale correlation using
Pearson’s correlation coefficient and Spearman’s p. For
the reliability study we used another sample of 58 Introduction
patients who received the WOMAC twice within 15
days. The Pearson’s, Spearman’s p, and intraclass
Despite the fact that health-related quality of life
correlation coefficients were calculated. Internal con-
(HRQoL) has long been the concern of healthcare
sistency was measured by Cronbach’s a. The respon-
clinicians and managers, over the last 30 years more
siveness study was carried out by resending the two
questionnaires to all patients 6 months after surgical publications have begun to appear on the subject in the
medical literature [1].
intervention; responsiveness was measured by means of
Although different types of outcome measures have
the paired t-test, the effect size I and the standardised
response mean. The Pearson’s coefficients for the been used to evaluate the effectiveness of both medical
and surgical interventions, the patient’s point of view is
convergent validity ranged from 70.52 to 70.63. The
now increasingly being considered. This is particularly
coefficients obtained for the item–scale correlation of the
pain area were 0.74 or higher, 0.91 or higher for true with regard to chronic pathologies that are basically
directed at improving or relieving symptoms. Instru-
stiffness, and 0.61 or higher for function. When
ments for measuring the HRQoL are one means to
measuring the test–retest reliability, the coefficients
evaluate the outcome based on patients’ opinions.
ranged from 0.66 to 0.81. Internal consistency yielded
a Cronbach’s a ranging from 0.81 to 0.93. The Various instruments have been created and validated
[2–5] to evaluate both the symptomatology and function
responsiveness showed an effect size I ranging from
on osteoarthritis (OA) of the hip or knee. However, the
1.5 to 2.2 in patients who underwent hip replacement;
for those who underwent knee replacement the range disease-specific questionnaire Western Ontario and
McMaster Universities (WOMAC) is the most widely
was 1 to 1.8. The standardised response mean ranged
used instrument for this purpose [6,7], and it has proved
from 1.3 to 1.9 for patients with hip OA; those with knee
to be the best for studies evaluating HRQoL after knee
replacement [8,9].
Correspondence and offprint requests to: Dr Antonio Escobar
Martınez, Unidad de Investigacion, Hospital de Basurto, Avenida de
´ ´ Considerable effort has been made to standardise the
Montevideo, 18, 48013 Bilbao, Spain. Tel: +34 944006000 ext. 5307; evaluation of the psychometric properties (validity,
Fax: +34 944006180; E-mail: aescobar@hbas.osakidetza.net reliability and responsiveness) of quality-of-life ques-

2. Validation of Spanish WOMAC 467
tionnaires to ensure that the versions of the questionnaire Statistical Analysis
that have been adapted for use in another language are
equivalent to the original questionnaire [10]. Descriptive data are expressed as percentages and
The goal of the present study was to evaluate the means, with a standard deviation for the population
validity, reliability and responsiveness of the Spanish studied.
version of the WOMAC questionnaire.
Psychometric Properties
Patients and Methods Validity To evaluate differences in mean scores between
the different groups of clinical severity (slight, moderate,
The sample consisted of 269 patients who underwent hip and severe), a one-way analysis of variance was carried
replacement (142) or knee replacement (127) surgery at out in the three WOMAC dimensions. We used
the Department of Orthopedics, Hospital of Basurto, Scheffe’s test for multiple comparisons.
´
between March 1999 and February 2000. This is a To determine the convergent and divergent validities
tertiary hospital covering a population of approximately we calculated Pearson’s correlated coefficient and
350.000 inhabitants of the Bilbao area. All patients Spearman’s p between the WOMAC dimensions and
fulfilled clinical and radiographic criteria for the the SF-36 scales, when the questionnaire was adminis-
diagnosis of primary OA, with just one joint affected. tered before surgery. Likewise, we evaluated the
We excluded patients who were unable to complete the WOMAC item–scale correlation using Pearson’s corre-
questionnaires either because of languge difficulties, a lation coefficient and Spearman’s p.
psychiatric disorder or sensory impairment. All patients
received a disease-specific questionnaire, WOMAC, and Reliability The reliability of the internal consistency of
a generic one, SF-36, as well as another series of the dimensions was assessed using Cronbach’s a
demographic and clinical questions by mail. Patients had coefficient.
to complete both questionnaires while they were on the To study test–retest reliability, we enrolled a different
waiting list for surgery and 6 months after surgery. sample of 92 patients who received the WOMAC
The classification into groups of severity (slight, questionnaire while they were on the waiting list for
moderate and severe) was established through questions surgery, and then again 15 days later while they were
not included in the WOMAC questionnaire, concerning still on the waiting list. They were explicitly asked
pain and the type of daily activities the person could whether they had experienced any change in their health
carry out. status since completing the previous questionnaire, with
The WOMAC is a disease-specific self-administered no change being detected. We calculated Pearson’s
questionnaire developed to study patients with hip or correlation coefficient, Spearman’s p coefficient and the
knee OA and requires about 5 min to complete. It has a intraclass correlation coefficient.
multidimensional scale made up of 24 items grouped
into three dimensions: pain (five items), stiffness (two Responsiveness To evaluate the changes produced after
items) and physical function (17 items). We used the surgery, the WOMAC questionnaire was sent again 6
Likert version with five response levels for each item, months [18,19] after discharge to the patients who
representing different degrees of intensity (none, mild, underwent hip or knee replacement surgery. The changes
moderate, severe or extreme) that were scored from 0 to were evaluated by three methods: the paired t-test; the
4. The final score for the WOMAC was determined by effect size I, or standardised effect size, defined as the
adding the aggregate scores for pain, stiffness and difference between the mean baseline scores and follow-
function. up scores on the measure, divided by the standard
The higher the score, the worse the patient’s deviation of the baseline scores; and the effect size II or
condition; therefore, an improvement was achieved by the standardised response mean, defined as the mean
reducing the overall score. The data were standardised to score change divided by the standard deviation of that
a range of values from 0 to 100, where 0 represents the score change [20]. According to the literature [21,22],
best health status and 100 the worst possible status. The values higher than 0.8 are proposed to represent high
original questionnaire is reliable, valid and sensitive to responsiveness.
the changes in the health status of patients with hip or
knee OA [2,11]. Moreover, several international
organisations have recommended this questionnaire for Results
evaluating OA [12,13], and it has been translated into
Spanish and adapted for the population of Spain [14]. Of the 269 patients who received both questionnaire, 203
The SF-36 is a generic questionnaire on HRQoL that (75.5%) were included in the study because they
has been translated into Spanish and validated [15]. The completed both the WOMAC disease-specific ques-
questionnaire evaluates eight dimensions regarding both tionnaire and the generic SF-36 questionnaire (Table 1)
physical and mental health and is widely used in HRQoL and underwent knee replacement surgery (n = 103) or
studies [16,17]. hip replacement (n = 100). The reliability study was

3. 468 A. Escobar et al.
Table 1. Baseline characteristics of the study population Table 2. Quality-of-life measure (mean + SD) using the WOMAC
scale, ordered by anatomic location and severity
Hip replacement Knee replacement
(n = 100) (n = 103) Pain Function Stiffness n
Mean age (yr) (SD) 68.6 (10.3) 70.9 (6) Hip*
Gender (%) Severity
Men 44 (44) 30 (29.1) Slight 32.9 (17.2) 44.2 (18.8) 34.4 (20) 12
Women 56 (56) 73 (70.9) Moderate 36.7 (9.4) 53.6 (12) 40.6 (17) 12
Severity (%) Severe 60.1 (16.9) 70.7 (14.6) 64.8 (22.7) 76
Slight 12 (12) 8 (7.8) Knee
Moderate 12 (12) 25 (24.3) Severity
Severe 76 (76) 70 (67.9) Slight 29.4 (15.4){ 35.8 (15.1){ 34.4 (21.9){ 8
WOMAC* Moderate 50.2 (17.3){ 54.8 (17){ 49.5 (18.6) 25
Pain 53.9 (19.4) 57 (18) Severe 62.6 (14.7){ 5.3 (15.4){ 61.8 (23.2){ 70
Function 65.4 (17.5) 60.5 (17.7)
Stiffness 58.3 (24.5) 56.7 (23.4) *.P<0.05 for differences between the severe–slight and severe–
moderate groups.
{
*.Standardised data from 0 to 100. Mean score + standard deviation. .P<0.0001 for differences between the three groups, except for
A higher score indicates a worse state. stiffness, where the difference is between slight and severe (P<0.05).
conducted based on a different sample of 58 patients out The WOMAC pain dimension correlated best with the
of 92 to whom were sent the WOMAC questionnaire SF-36 bodily pain scale (r = 70.6, p = 70.55)
while on the waiting list (63%). compared with the rest of the scales (Tables 3). The
function dimension of the WOMAC questionnaire
achieved the highest Pearson correlation coefficient of
Validity 70.63 (p = 70.59) with the SF-36 pain scale, whereas
this coefficient was 70.52 (p = 70.59) with the
The descriptive data for the mean score, as well as the physical function scale of the same questionnaire. The
standard deviation for each of the WOMAC dimensions stiffness dimension obtained coefficients of r = 70.5
ordered by anatomic location of the illness and its (p = 70.48) with the bodily pain scale of the SF-36. The
severity, are shown in Table 2. The results showed an coefficients are negative, given the fact that for the
increase in the score for each domain as the severity of the WOMAC questionnaire, compared with the SF-36, the
illness increased for both anatomic locations. For patients scores decrease with improvements in the HRQoL. All
with knee OA, the differences were statistically sig- correlations were significant (P<0.0001).
nificant between all levels of severity, except for the Regarding the item–domain correlation, the five items
group classified as moderate on the stiffness dimension. in the pain dimension obtained coefficients of more than
In patients with hip OA, statistically significant differ- 0.74 (P<0.0001) with their dimension, which was lower
ences were observed between the severe and slight groups with the other two dimensions (stiffness and function).
and the severe and moderate groups; no differences were The two items on stiffness obtained coefficients of more
seen between the moderate and slight groups. than 0.91 (P<0.0001) with their own dimension, which
Table 3. Convergent and divergent validities: Pearson’s correlation coefficient (Spearman’s p)
WOMAC SF-36
Pain Function Stiffness BP PF RP GH VT SF RE MH
WOMAC
Pain 71
Function 70.79 71
Stiffness 70.57 70.71 71
SF-36
BP 70.6 (70.55) 70.63 (70.59) 70.5 1
PF 70.4 70.52 (70.59) 70.38 0.39 1
RP 70.35 70.43 70.33 0.45 0.27 1
GH 70.33 70.34 70.22 0.35 0.28 0.26 1
VT 70.47 70.5 70.37 0.61 0.37 0.38 0.5 1
SF 70.45 70.52 70.4 0.54 0.34 0.41 0.37 0.57 1
RE 70.31 70.31 70.27 0.28 0.12 0.25 0.37 0.37 0.43 1
MH 70.41 70.43 70.33 0.43 0.3 0.4 0.5 0.64 0.57 0.57 1
All the correlations were significant (P<0.0001).
BP, bodily pain; PF, physical functioning; RP, role-physical; GH, general health; VT, vitality; SF, social functioning; RE, role-emotional; MH,
mental health.

4. Validation of Spanish WOMAC 469
were lower with the other two dimensions. Finally, for Internal consistency, evaluating using Cronbach’s a
the 17 items in the function dimension, all but two coefficient, gave values of 0.82 for pain, 0.93 for
obtained coefficients of more than 0.61 (P<0.0001). The function, and 0.81 for stiffness.
two items were: What degree of difficulty do you have
descending stairs? and What degree of difficulty do you
have standing? and obtained 0.54 and 0.55, respectively,
although they correlated better with the pain dimension Responsiveness
(r = 0.59 and r = 0.63, respectively). The data for
Spearman’s correlation coefficient gave the same results.
All patients underwent either hip or knee replacement
surgery. Six months after surgery they again received
Reliability both the WOMAC and SF-36. A significant statistical
improvement was observed (P<0.001) in the three
To assess the test–retest reliability of the WOMAC WOMAC dimensions and in the SF-36 in patients who
questionnaire in the sample of 58 patients, we used underwent hip replacement (Table 5) and those who
Pearson’s correlation coefficient, Spearman’s p coeffi- underwent knee replacement (Table 6). The effect size I
cient and the intraclass correlation coefficient. The values for patients with a hip replacement were 1.9 for
descriptive data for the pre and post scores, as well as pain, 2.2 for function and 1.5 for stiffness. For those who
the corresponding coefficients, are given in Table 4. The underwent knee replacement surgery, the values were
coefficients ranged from 0.66 to 0.81, with the lower 1.8, 1.5 and 1, respectively. The effect size II values, or
ones corresponding to stiffness and the higher ones to the standardised response means, for patients who
function. All coefficients were statistically significant underwent hip replacement were 1.8 for pain, 1.9 for
(P<0.0001). function and 1.3 for stiffness. For patients who under-
Table 4. Analysis of WOMAC’s test–retest reliability
WOMAC Test Retest Correlation coefficient
¯
X (D.E.) ¯
X (D.E.)
Pearson p Intraclass Cronbach’s a
Pain 53 (18.4) 51.7 (20) 0.78 0.79 0.78 0.82
Function 62.1 (16.4) 62.6 (17.6) 0.81 0.81 0.81 0.93
Stiffness 63.4 (24) 62.1 (21.2) 0.67 0.66 0.67 0.81
All coefficients were statistically significant (P<0.0001).
Table 5. Changes in the HRQoL measured by WOMAC in patients who underwent hip replacement
Variable Pre intervention Post intervention Difference P SRM* Effect size I
¯
X (D.E.) ¯
X (D.E.) ¯
X (D.E.)
WOMAC
Pain 53.9 (19.4) 16.2 (16) 37.7 (20.5) <0.0001 1.8 1.9
Function 65.3 (17.5) 27.4 (17.7) 37.9 (19.9) <0.0001 1.9 2.2
Stiffness 58.3 (24.5) 22.4 (18.4) 35.9 (26.8) <0.0001 1.3 1.5
SE-36
Bodily pain 30.7 (27.1) 58.4 (28.4) 27.3 (30.3) <0.0001 0.9 1
Physical functioning 19.8 (19.1) 48.7 (22.4) 28.9 (25.7) <0.0001 1.1 1.5
Table 6. Changes in HRQoL measured by WOMAC in patients who underwent knee replacement
Variable Pre intervention Post intervention Difference P SRM* Effect size I
¯
X (D.E.) ¯
X (D.E.) ¯
X (D.E.)
WOMAC
Pain 53.0 (18.0) 24.4 (17.6) 32.6 (21.9) <0.0001 1.5 1.8
Function 60.3 (17.7) 32.7 (18.7) 27.6 (21.8) <0.0001 1.3 1.5
Stiffness 56.7 (23.4) 33.0 (22.2) 23.7 (31.1) <0.0001 0.8 1
SE-36
Bodily pain 34.7 (28.2) 51.1 (28.9) 15.6 (34.1) <0.0001 0.5 0.5
Physical functioning 25.0 (21.6) 50.2 (24.5) 25.2 (27.1) <0.0001 0.9 1.2
*.Standardised response mean or effect size II.

5. 470 A. Escobar et al.
went knee replacement, the values were 1.5, 1.3 and 0.8, both cases. This could be a result of the fact that the data
respectively. The results for the SF-36 were lower for all do not have a normal distribution and are similar to those
indicators. described [24].
The divergent validity was studied according to levels
of severity. Regarding the patients who underwent hip
replacement surgery, no statistically significant differ-
Discussion ences were found between slight and moderate severity,
which could be the result of the small number of patients
in both groups.
Hip and knee OA is a chronic illness that, despite being Reliability is another psychometric characteristic to be
non-life-threatening, does cause morbidity: it has an evaluated in a questionnaire. A reliable measurement is
important social impact, and in many cases it leads to a one that produces the same results when it is
hip or knee replacement to improve the patient’s quality administered two or more times under the same
of life [23]. conditions. In the present study the questionnaire was
Various instruments have been used to measure
sent to the patients a second time, 15 days after they had
HRQoL in these orthopaedic patients [22,24]; however,
the WOMAC questionnaire is the disease-specific replied to the first one. They were asked whether they
instrument most widely used in clinical practice for had experienced any change that could affect their
outcome measurement [6,7]. health; a negative response was obtained from all
The advantages of disease-specific questionnaires patients. The values of all the reliability coefficients
such as the WOMAC are derived from the fact that indicate that the dimensions are coherent, they are
they are more closely focused on the illness or similar to those obtained for the Swedish version of the
impairment under study (in this case OA) and should questionnaire [28], and are slightly lower than those
be better at detecting the changes resulting from obtained for the Hebrew version with regard to internal
treatment than questionnaires that are not disease consistency [29].
specific. The disadvantge is that they cannot detect The instrument’s responsiveness presents more diffi-
other types of impairment or complications in areas or culties regarding both its concept and the way in which
organs that are not specifically related to the illness to measure or quantify it. In our study we measured the
under study [24] that could be important to the patient. so-called internal responsiveness, defined as the ability
To adequately compare the studies carried out in of a measure to change over a specific period [20]. All
different countries, the versions of the questionnaires the results of the WOMAC questionnaire showed good
should be adapted and validated. Although the WOMAC responsiveness and therefore a significant improvement
questionnaire has been translated and adapted for a in the patients’ health states after knee or hip
Spanish population [14] its psychometric properties have replacement surgery, with values higher than those
not been studied, and this was the goal of this present shown by other authors [27]. As observed in Tables 5
study. and 6, these changes were greater than those for the SF-
The psychometric properties of the questionnaires 36. This confirms that the disease-specific instrument is
measuring the HRQoL are established by studying their more sensitive to changes experienced by patients than
validity, reliability and responsiveness. the generic questionnaire for the corresponding scales.
There are various ways of determining the validity of These data confirm the data obtained in other studies that
a questionnaire, one of which is convergent and have used the same questionnaires to make a comparison
divergent validity. This is generally done by comparing [9,24].
the instrument under study with other instruments that A possible limitation in the use of the WOMAC
have already been validated. The SF-36 is a widely used questionnaire is the age of the population to which it was
instrument [25,26] and has been validated in Spanish
directed, particularly in the case of patients who
[14]. Our data on validity present moderate correlations
underwent hip or knee replacement, as age does not
when the dimensions of both questionnaires were
compared, with correlation coefficients ranging from limit the indication for surgery [6,30], and for older
70.4 to 70.6, which agrees with other studies [27,28]. people it is possible to limit both the number of
As expected, for both Pearson’s coefficient and responses as well as the interpretation of some items.
Spearman’s p the WOMAC pain dimension obtained A further limitation is that the responses may be
the best correlation with the SF-36 bodily pain scale influenced by another type of problem, such as back
compared with the rest of the scales. For the stiffness pain [31], which is common in our practice.
dimension, the highest coefficient values were found in In conclusion, the Spanish version of the WOMAC
the bodily pain scale with both coefficients. When disease-specific questionnaire offers psychometric prop-
analysing the data for the function dimension, we erties that make it a valid, reliable and responsive
oberved that it correlated best with the bodily pain and instrument for patients with hip or knee OA who have
function scales of the SF-36 (r = 70.63 and r = 70.52, undergone a hip or knee replacement. A generic
respectively), although with Spearman’s coefficient this instrument that measures different but complementary
relation changed slightly, with coefficients of 70.59 in health areas should accompany it.

6. Validation of Spanish WOMAC 471
References 17. Kosinski M, Keller SD, Hatoum HT, Kong SX, Ware JE Jr. The
SF-36 Health Survey as a genereic outcome measure in clinical
1. Alonso J. La medida de la calidad de vida relacionada con la trials of patients with osteoarthritis and rheumatoid arthritis: tests
salud en la investigacio y la practica clınica. Gac Sanit
´n ´ ´ of data quality, scaling assumptions and score reliability. Med
2000;14:163–7. Care 1999;37(5 Suppl):MS10–MS22.
2. Bellamy N, Buchanan WW, Goldsmith CH, Campbell J, Stitt 18. Jones CA, Voaklander DC, Johnston DW, Suarez-Almazor ME.
LW. Validation study of WOMAC: a health status instrument for Health related quality of life outcomes after total hip and knee
measuring clinically important patient relevant outcomes to arthroplasties in a community based population. J Rheumatol
antirheumatic drug therapy in patients with osteoarthritis of the 2000;27:1745–52.
hip or knee. J Rheumatol 1988;15:1833–40. 19. Brazier JE, Harper R, Munro J, Walters SJ, Snaith ML. Generic
3. Lequesne MG, Mery C, Samson M, Gerard P. Indexes of severity and condition-specific outcome measures for people with
for osteoarthritis of the hip and knee. Scand J Rheumatol osteoarthritis of the knee. Rheumatology (Oxford) 1999;38:870–
1987;65(Suppl):85–9. 7.
4. Wright JG, Young NL. The patient-specific index: asking patients 20. Husted JA, Cook RJ, Farewell VT, Gladman DD. Methods for
what they want. J Bone Joint Surg [Am] 1997;79:974–83. assessing responsiveness: a critical review and recommendations.
5. Meenan RF, Gertman MP, Mason JH. Measuring health status in J Clin Epidemiol 2000;53:459–68.
arthritis. The Arthritis Impact Measurement Scales. Arthritis 21. Garratt AM, Ruta DA, Abdalla MI, Russell IT. SF 36 health
Rheum 1980;23:146–52. survey questionnaire: II. Responsiveness to changes in health
6. Anderson JG, Wixson RL, Tsai D, Stulberg SD, Chang RW. status in four common clinical conditions. Qual Health Care
Functional outcome and patient satisfaction in total knee patients 1994;3:186–92.
over the age of 75. J Arthroplasty 1996;11:831–40. 22. Beaton DE, Hogg-Johnson S, Bombardier C. Evaluating changes
7. Hawker G, Wright J, Coyte P et al. Health-related quality of life in health status: reliability and responsiveness of five generic
after knee replacement. J Bone Joint Surg [Am] 1998;80:163–73.
health status measures in workers with musculoskeletal disorders.
8. Brazier JE, Harper R, Munro J, Walters SJ. Snaith ML. Generic
and condition-specific outcome measures for people with J Clin Epidemiol 1997;50:79–93.
osteoarthritis of the knee. Rheumatology (Oxford) 1999;38:870– 23. Rissanen P, Aro S, Sintonen H, Slatis P, Paavolainen P. Quality of
7. life and functional ability in hip and knee replacements: a
9. Hawker G, Melfi C, Paul J, Green R, Bombardier C. Comparison prospective study. Qual Life Res 1996;5:56–64.
of a generic (SF-36) and a disease specific (WOMAC) (Western 24. Bombardier C, Melfi CA, Paul J et al. Comparison of a generic
Ontario and McMaster Universities Osteoarthritis Index) instru- and a disease-specific measure of pain and physical function after
ment in the measurement of outcomes after knee replacement knee replacement surgery. Med Care 1995;33(4 Suppl):AS131–
surgery. J Rheumatol 1995;22:1193–6. AS144.
10. Lamarca R, Alonso J, Santed R, Prieto L. Performance of a 25. Boardman DL, Dorey F, Thomas BJ, Lieberman JR. The
perceived health measure in different groups of the population: a accuracy of assessing total hip arthroplasty outcomes: a
comprehensive stuy in Spain. J Clin Epidemiol 2001;54:127–35. prospective correlation study of walking ability and 2 validated
11. Bellamy N. Pain assessment in osteoarthritis: experience with the measurement devices. J Arthroplasty 2000;15:200–4.
WOMAC osteoarthritis index. Semin Arthritis Rheum 1989;18(4 26. Quintana JM, Arostegui I, Azkarate J et al. Evaluation of explicit
Suppl 2):14–17 criteria for total hip joint replacement. J Clin Epidemiol
12. Recommendations for the registration of drugs used in the 2000;53:1200–8.
treatment of osteoarthritis. Group for the respect of ethics and 27. Roos EM, Klassbo M, Lohmander LS. WOMAC osteoarthritis
excellence in science (GREES): osteoarthritis section. Ann index. Reliability, validity, and responsiveness in patients with
Rheum Dis 1996;55:552–7. arthroscopically assessed osteoarthritis. Western Ontario and
13. Altman R, Brandt K, Hochberg M et al. Design and conduct of MacMaster Universities. Scand J Rheumatol 1999;28:210–15.
clinical trials in patients with osteoarthritis: recommendations 28. Soderman P, Malchau H. Validity and reliability of Swedish
from a task force of the Osteoarthritis Research Society. Results WOMAC osteoarthritis index: a self-administered disease-
from a workshop. Osteoarthritis Cartilage 1996;4:217–43.
specific questionnaire (WOMAC) versus generic instruments
14. Batlle-Gualda E, Esteve-Vives J, Piera MC, Hargreaves R, Cutts
(SF-36 and NHP). Acta Orthop Scand 2000;71:39–46.
´ ´ ˜ol
J. Traducion y adaptacion al espan del cuestionario WOMAC
especıfico para artrosis de rodilla y cadera. Rev Esp Reumatol
´ 29. Wigler I, Neumann L, Yaron M. Validation study of a Hebrew
1999;26:38–45. version of WOMAC in patients with osteoarthritis of the knee.
˜
15. Alonso J, Prieto L, Anto JM. La version espanola del SF-36
´ Clin Rheumatol 1999;18:402–5.
Health Survey (Cuestionario de Salud SF-36): un instrumento 30. Dalury DF, Ewald FC, Christie MJ, Scott RD. Total knee
para la medida de los resultados clınicos. Med Clin (Barc)
´ arthroplasty in a group of patients less than 45 years of age. J
1995;104:771–6. Arthroplasty 1995;10:598–602
16. Kiebzak GM, Vain PA, Gregory AM, Mokris JG, Mauerhan DR. 31. Wolfe F. Determinants of WOMAC function, pain and stiffness
SF-36 general health status survey to determine patient scores: evidence for the role of low back pain, symptom counts,
satisfaction at short-term follow-up after total hip and knee fatigue and depression in osteoarthritis, rheumatoid arthritis and
arthroplasty. J South Orthop Assoc 1997;6:169–72. fibromyalgia. Rheumatology (Oxford) 1999;38:355–61.
Received for publication 12 November 2001
Accepted in revised form 21 May 2002