Objectives: The goal of this work is to analyze the issue of return to professional activity by working-age patients who have been treated surgically with total knee arthroplasty (TKA) due to gonarthrosis. Material and Methods: Overall, 88 working-age patients were examined, with a total of 91 TKA procedures performed due to advanced gonarthrosis. The average age of the patients was 54.2 years for women and 58.1 years for men. A modified Knee Society Score scale was used to compile the results of the clinical trial. The Kellgren-Lawrence classification was used to assess preoperative radiographs. Postoperative radiographs evaluated the position of the endoprosthesis of both the femoral and tibial components in the anteriorposterior and lateral upright projections. The obtained results were subjected to statistical analysis. Results: In the preoperative assessment, both the clinical and radiological results obtained were unfavorable in all cases. Throughout the observation period of approximately over 3.8 years, a very good result was noted in 65 cases (71.4%), a good result in 20 cases (22%), and a satisfactory result in 6 cases. There were no bad results. The average improvement on the Visual Analogue Scale was 6.5 pts. The radiological assessment did not reveal any radiological symptoms of the aseptic loosening of the endoprosthesis, simultaneously concluding that each time the endoprosthesis components were properly seated. Only 53 (58.3%) of the examined patients were professionally active before the surgery. After completing the treatment, 46 (50.5%) of all patients returned to work, in favor of intellectual workers. The average duration of sick leave was 136.2 days, and rehabilitation allowance was granted in 19 cases. Conclusions: Firstly, in working-age patients, TKA is a valuable method for surgical treatment of advanced gonarthrosis of varying etiology. Secondly, most of the patients who worked before the surgery returned to performing work in the position held and on the same full-time equivalent basis. Int J Occup Med Environ Health. 2021;34(5):617–28