BackgroundHealth-related quality of life (HRQoL) following total hip and knee arthroplasty (THA/TKA) may decline more in Asian countries due to lifestyle and housing factors compared with patients in Western countries. AimsTo evaluate the psychometric properties of the Japanese version of 15D and clarify the characteristics of HRQoL in Japanese patients who underwent THA/TKA compared with Finnish patients. MethodsThis longitudinal study included 182 patients between 2019 and 2021. Patients' HRQoL was measured using the 15D preoperatively and 3 months postoperatively. Student's t-tests were used to compare lifestyles between Japan and Finland. ResultsThe Japanese version of the 15D showed good internal consistency, reliability, construct validity, and responsiveness. Patients with many steps inside their house had worse HRQoL in the dimensions of mobility, distress, and vitality in Japan. There were significant differences in mobility, distress, vitality, and sexual activity dimensions between Japan and Finland 3 months postoperatively. ConclusionsThe lower HRQoL in Japan in the dimensions of mobility, distress, and vitality is likely due to Japan's traditional housing structure with many steps. Identifying differences in cultural and psychological characteristics, as well as by residential setting, will enable health care providers to help patients improve their HRQoL.