1 3 Rheumatol Int (2016) 36:1455–1458 DOI 10.1007/s00296-016-3505-4 Rheumatology INTERNATIONAL VALIDATION STUDIES Cross-cultural adaptation and validation of the reliability of the Thai version of the Hip disability and Osteoarthritis Outcome Score (HOOS) Warayos Trathitiphan 1 · Permsak Paholpak 1 · Winai Sirichativapee 1 · Taweechok Wisanuyotin 1 · Pat Laupattarakasem 1 · Kamolsak Sukhonthamarn 1 · Polasak Jeeravipoolvarn 1 · Weerachai Kosuwon 1 Received: 7 January 2016 / Accepted: 25 May 2016 / Published online: 4 June 2016 © Springer-Verlag Berlin Heidelberg 2016 pain subscale of the Thai HOOS had a high correlation with the Vitality and Social Function subscales of the Thai SF-36 (r = 0.55 and 0.54)—with which the symptom subscale had a moderate correlation. The Thai version of HOOS had excellent internal consistency, excellent test–retest reliability, and good construct validity. It can be used as a reliable tool for assessing quality of life for patients with hip osteoarthritis in Thailand. Keywords HOOS · Thai · Reliability · Validity · Cross- cultural adaptation Introduction The Hip disability and Osteoarthritis Outcome Score (HOOS) questionnaire was developed for developed for measuring symptoms and functional limitations related to hip in patients with hip osteoarthritis [1]. The HOOS represents an improve- ment on the Western Ontario and McMaster Universities Oste- oarthritis Index (WOMAC) [2]; in terms of validity among young and active patients with high functional demand [1]. The HOOS questionnaire has been translated into French, Dutch, German, Chinese, Turkish, Japanese, and Korean [3–8]. It has not, however, been translated and tested for use in Southeast Asia, where the incidence of hip OA and socioeconomic and cultural factors are different. The aim of this study was to translate the HOOS into Thai— in accordance with international publishing recommenda- tions—and to test its reliability and validity in the Thai context. Methods This is a reliability and validity testing of Thai HOOS questionnaire. Abstract HOOS was developed as an extension of the West- ern Ontario and McMaster Universities’ Osteoarthritis Index questionnaire for measuring symptoms and functional limita- tions related to the hip(s) of patients with osteoarthritis. To determine the validity and reliability of the Thai version of the Hip disability and Osteoarthritis Outcome Score (HOOS) vis-à-vis hip osteoarthritis, the original HOOS was translated into a Thai version of HOOS, according to international recom- mendations. Patients with hip osteoarthritis (n = 57; 25 males) were asked to complete the Thai version of HOOS twice: once then again after a 3-week interval. The test–retest reli- ability was analyzed using the intraclass correlation coefficient (ICC). Internal consistencies were analyzed using Cronbach’s alpha, while the construct validity was tested by comparing the Thai HOOS with the Thai modified SF-36 and calculating the Spearman’s rank correlation coefficients. The Thai HOOS produced good reliability (i.e., the ICC was greater than 0.9 in all five subscales). All of the Cronbach’s alpha showed that the Thai HOOS had high internal consistency (Cronbach’s alpha greater than 0.8), especially for the pain and ADL subscales (0.89 and 0.90, respectively). The Spearman’s rank correlation for all five subscales of the Thai HOOS had moderate corre- lation with the Bodily Pain subscale of the Thai SF-36. The Warayos Trathitiphan and Permsak Paholpak are co-first authors and they contributed equally to this paper. Electronic supplementary material The online version of this article (doi:10.1007/s00296-016-3505-4) contains supplementary material, which is available to authorized users. * Weerachai Kosuwon weera_ko@kku.ac.th 1 Department of Orthopedics, Faculty of Medicine, Khon Kaen University, 123, Khon Kaen 40002, Thailand