Osteoarthritis (OA) is a degenerative, progressive, inflammatory disease of the musculoskeletal system with a rheumatic factor characterized by pain, loss of mobility, reduction of functional activities, muscle atrophy and stiffness of the affected joint. Knee and/or hip OA is the biggest cause of functional limitations and physical disability in adults compared to other chronic diseases. The treatment of OA includes a multidisciplinary approach with a combination of pharmacological and non-pharmacological therapy consisting of lifestyle changes and the implementation of physiotherapy interventions. It strives for timely detection of diseases, reduction of pain, prevention of joint contractures and maintenance of mobility, strength and mobility of muscles. The thesis includes research that was carried out at the Dubrava Clinical Hospital in the Department for Osteoarthritis. The aim of the research was to compare the quality of functional activities and the level of pain before and after physiotherapy interventions. Based on that, two hypotheses were put forward. The first is that physiotherapy intervention has a positive effect on functional activities in patients with hip and knee osteoarthritis. The second hypothesis states that physiotherapy intervention reduces the level of pain in the same patients. In the period between April and May 2023, 40 respondents participated in the research, with whom physiotherapy intervention was carried out. It included medical exercises for breathing, mobilization, strength and balance and 2 physical procedures: magnetotherapy and electrotherapy. The daily intervention lasted a total of 45 minutes, and the patients came to therapy 5 times a week for a period of two weeks. The first and final measurements were examined with WOMAC questionnaires and the VAS scale for the variables of functional activities and pain levels upon arrival of the patients before and after the intervention. The results of the statistical processing confirmed both hypotheses: functional activity is better after the physiotherapy interventions p = 0.001 (p<0.05), and the pain level is lower compared to the initial measurement p = 0.001 (p<0.05). Physiotherapy intervention significantly improves functional activity and reduces pain levels in patients with hip and knee osteoarthritis.