Introduction: Hip osteoarthritis manifests itself with pain, limitation of the range of motion, weaker muscles and pathological gait pattern. Total hip arthroplasty is a treatment of choice which leads to pain relief and improvement in patients' functioning. The aim of the work was to assess the influence of total hip arthroplasty on the reduction in patients' disability. Material and methods: The study group included 30 patients aged 62.53 ± 12.79. Mean body height was 168.03 ± 8.83 cm, while mean body mass was 78.47 ± 12.86 kg. Patients were examined twice, i.e. before the surgery and three months post surgery. In order to assess disability levels, two scales were applied, i.e. Western Ontario and McMaster Universities Arthritis Index (WOMAC) and modified Harris Hip Score (HHS). Results: Total hip arthroplasty significantly reduced the patients' disability. Prior to the surgery, the mean results of HHS were at the level of 37.07 ± 14.47 points. After the surgery, the patients scored 74.93 ± 24.12 points. In WOMAC, the study participants scored an average of 61.7 ± 20.82 points before the surgery and 19.78 ± 26.31 points after the surgery. No correlations of the respondents' BMI and the duration of pain with the level of improvement resulting from the surgical treatment were noted either in HHS or in WOMAC. A positive correlation was found between the age of the respondents and the level of improvement in HHS. Conclusions: Total hip arthroplasty significantly reduced the patients' disability three months after the surgery. No correlations of the respondents' BMI and the duration of pain with the level of improvement in their physical fitness were noted.