Evaluation of health-related quality of life is an established criterion for the evaluation of therapeutic outcome. Specifically, while there are a great number of different questionnaires, in English, for this purpose, there is a lack of comparable questionnaires in Thai. The objectives of the present study were twofold: (1) to translate the original, English-language, 12-item Oxford (Oxford-12) outcome questionnaire and Short Form 36 (SF-36) general health questionnaire into a standard Thai version, and (2) to assess reliability of these two questionnaires and correlation between them among 100 patients having total knee replacement (TKR). Patients’ mean age was 63 years and 86% were female.
Oxford-12 revealed that patients had mild problems in terms of function and pain with the average function and pain score of 15.0 and 8.8 compared to maximum possible score of 35 and 25 respectively.
Oxford-12 was very reliable with Cronbach’s alpha for function, pain and total score of 0.819, 0.874 and 0.918 respectively.
For 8 health domains of SF-36 including physical functioning (PF), role physical (RP), bodily pain (BP), general health (GH), vitality (VT), social functioning (SF), role emotional (RE), and mental health (MH), patients had the highest score (i.e., good health) for VT, followed by MH, but lowest for PF. This resulted
in a higher score for mental component summary (MCS) than physical component summary (PCS). Cronbach’s alpha for 8 health domains varied from 0.651 (VT) to 0.996 (RP). Since a low score of Oxford-12 indicates a better state of health compared to high score for SF-36, negative correlation between them was expected. PF of SF-36 had the highest negative correlation with both Oxford function and pain with Pearson’s correlation coefficient (r) of -0.69 and -0.72 respectively. PCS was correlated well with both Oxford function and pain with r of -0.73 and -0.76 respectively whereas correlation between MCS and Oxford function and pain were only -0.60 and -0.58 respectively. Thai versions of Oxford-12 and SF-36 retain their original characteristics and are reliable for assessing the quality of life after TKR in Thai speaking patients.

Keywords: Validation, Thai translation, TKA (Total Knee Arthroscopy), Reliability of translation, Oxford knee score, SF 36 (Short from 36 general health outcome), Quality of life questionnaire, General health questionnaire, Cronbach’s alpha coefficient