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Table 2 Factor loadings, eigenvalues, percentage of explained variance and Cronbach’s alpha for the final TOA questionnaire

From: Development of the “Treatment beliefs in knee and hip OsteoArthritis (TOA)” questionnaire

Module 1: Physical activities
Items Factor loadings
 M1 = Module 1, Q = Question number (see Additional file 1 ) Factor I Factor II
 M1Q32: I learn to deal with my symptoms better by doing physical activities .77  
 M1Q19: I can do household chores better by doing physical activities .72  
 M1Q22: Doing physical activities produces good results at my age .71  
 M1Q33: I can do my job better by doing physical activities .70  
 M1Q39: I can tailor doing physical activities to my goals .63  
 M1Q10: I can postpone surgery by doing physical activities .53  
 M1Q14: I can do physical activities together with others .48  
 M1Q8: The only way to reduce my OA symptoms is by doing physical activities .47  
 M1Q20: I enjoy doing physical activities .45  
 M1Q24: By doing physical activities I will overload my knee/hip   .72
 M1Q23: I think that doing physical activities causes pain   .66
 M1Q7: I think that doing physical activities involves risks   .65
 M1Q28: I am scared to do physical activities   .55
 Eigenvalue 4.03 1.06
 Percentage of variance 31% 8%
 Cronbach’s Alpha .84 .79
 Correlation between factors −.51
Module 2: Pain medication
Items Factor loadings
 M2 = Module 2, Q = Question number (see Additional file 1 ) Factor I Factor II
 M2Q10: I can move more freely by using painkillers .80  
 M2Q18: I can do household chores better by using painkillers .76  
 M2Q2: My quality of life increases by using painkillers .74  
 M2Q20: Using painkillers produces good results at my age .73  
 M2Q9: I can postpone surgery by using painkillers .50  
 M2Q15: Using painkillers is harmful to my health   .70
 M2Q6: I think that using painkillers involves risks   .67
 M2Q11: I think that painkillers have side-effects   .64
 M2Q28: I think that using painkillers is invasive   .52
 M2Q25: I am scared to use painkillers   .47
 M2Q19: I think that using painkillers leads to habituation   .38
 M2Q22: By using painkillers I will overload my knee/hip   .35
 Eigenvalue 2.74 2.00
 Percentage of variance 23% 17%
 Cronbach’s Alpha .82 .72
 Correlation between factors −.14
Module 3: Physiotherapy
Items Factor loadings
 M3 = Module 3, Q = Question number (see Additional file 1 ) Factor I Factor II
 M3Q23: Doing physiotherapy produces good results at my age .86  
 M3Q20: I can do household chores better by physiotherapy .85  
 M3Q34: I can do my job better by physiotherapy .76  
 M3Q3: My quality of life increases by physiotherapy .71  
 M3Q22: I need to actively get going with physiotherapy myself .60  
 M3Q10: I can postpone surgery by physiotherapy .52  
 M3Q25: By physiotherapy I will overload my knee/hip   .71
 M3Q24: I think that physiotherapy causes pain   .70
 M3Q7: I think that physiotherapy involves risks   .62
 Eigenvalue 3.49 1.09
 Percentage of variance 39% 12%
 Cronbach’s Alpha .86 .74
 Correlation between factors −.36
Module 4: Injections
Items Factor loadings
 M4 = Module 4, Q = Question number (see Additional file 1 ) Factor I Factor II
 M4Q33: I can do my job better by an injection .89  
 M4Q20: I can do household chores better by an injection .88  
 M4Q3: My quality of life increases by an injection .76  
 M4Q30: An injection gives quick results .76  
 M4Q10: I can postpone surgery by an injection .62  
 M4Q31: I think that an injection can be repeated .47  
 M4Q24: By an injection I will overload my knee/hip   .62
 M4Q15: I am becoming dependent on an injection   .61
 M4Q34: An injection damages my knee/hip   .60
 M4Q32: I think that an injection is invasive   .54
 M4Q7: I think that an injection involves risks   .48
 M4Q40: An injection takes a lot of my time   .38
 Eigenvalue 3.54 1.78
 Percentage of variance 30% 15%
 Cronbach’s Alpha .87 .72
 Correlation between factors −.11
Module 5: Arthroplasty
Items Factor loadings
 M5 = Module 5, Q = Question number (see Additional file 1 ) Factor I Factor II
 M5Q4: My pain increases by a joint replacement −.61  
 M5Q9: My knee/hip deteriorates faster by a joint replacement −.51  
 M5Q10: I can move more freely after a joint replacement .78  
 M5Q17: I can do household chores better after a joint replacement .77  
 M5Q18: A joint replacement produces good results at my age .81  
 M5Q21: More people with OA choose to do a joint replacement .43  
 M5Q29: I think that a joint replacement can be repeated .45  
 M5Q38: I think that an artificial joint lasts a long time .44  
 M5Q1: I think a joint replacement is painful   .51
 M5Q23: I think an artificial joint carries the chance of an infection   .57
 M5Q24: I think a joint replacement carries the chance of an infection   .67
 M5Q27: A joint replacement takes up my energy   .53
 M5Q30: I think that a joint replacement is invasive   .62
 M5Q37: A joint replacement takes a lot of my time   .60
 Eigenvalue 3.13 2.14
 Percentage of variance 22% 15%
 Cronbach’s Alpha .81 .75
 Correlation between factors −.03