Contemporary health care practice emphasizes the importance of patient self-reported outcome measures. In order to assess the postoperative results of hip operations and to evaluate various pathological conditions of the hip in adult patients, a questionnaire known as the Harris Hip Score (HHS) was developed. The Modified Harris Hip Score (mHHS) was developed in 2000 for the long-term assessment of patients who underwent hip arthroscopy and can be filled in by a physician or physiotherapist. Thus, it becomes the preferred choice for evaluating the results of hip surgery, including arthroscopy and arthroplasty. The questionnaire was translated from the original English language, adapted linguistically and finally validated in several world languages, such as Italian, Spanish, Portuguese, Turkish, Arabic and Slovenian. The paper describes the localization process of the mHHS questionnaire into the Croatian language with cultural adaptations, and the existence of a connection between the total number of points of the patient's self-assessment of gait and activity with physiotherapy measurements of range of motion and muscle strength was investigated. After analyzing the collected data using descriptive statistics methods, it was concluded that there is a consistent connection between the total score of the mHHS questionnaire for the hip and physiotherapy measurements. This is shown by the achievement of a higher number of points in the questionnaire, which proportionally results in better results of measuring the range of motion and muscle strength.