Osteoarthritis is one of the main causes of pain and functional disorders in society, one that often affects the performance of everyday activities. The treatment usually consist of physiotherapy and pharmacotherapy, while in advanced stages, surgical treatment is required. The common method to assess the effectiveness of treatment is the physical examination by standardized scales of quality of life, assessment of pain and functioning. More recently, advances in objective assessment tools have been included such as DIERS formetric III 4D, myotometry or bioimpedance. The aim of the study is to evaluate the functional assessment of patients after hip and knee arthroplasty performed due to osteoarthritis. Hip and knee arthroplasty clearly improves the functioning of patients, reduces the intensity of pain and the risk of falls. In addition, changes in muscle tone and stiffness were demonstrated before and after the arthroplasty of the lower limbs.