The aim of the study was to analyze our own experience of using the lateral approach in knee joint arthroplasty in children with oncopathology. Materials and methods of research: the results of a retrospective nonrandomized uncontrolled single-center study are analyzed, within the framework of which 97 endoprosthetics of the knee joint were performed in children and adolescents with oncological pathology over 7 years (2012–2018). Lateral approach was used in 28 patients. The functional results were assessed using the MSTS rating scale 6 and 12 months after the surgery. Postoperative complications were analyzed according to the Henderson classification (modified by the ISOLS committee). Results: when comparing the functional outcome depending on the surgical approach, no statistically significant difference was found either after 6 months (p=0,124) or after 12 months (p=0,755). There is no more frequent development of complications detected (p=0,551). The access used also did not affect overall survival in osteosarcoma (p=0,577), in Ewing's sarcoma (p=0,493), as well as on event-free survival in osteosarcoma (p=0,829) and in Ewing's sarcoma (p=0,886). Conclusion: the use of the lateral surgical approach for knee arthroplasty in children with oncopathology does not affect the treatment results, however, it provides the surgeon with greater variability of actions during preoperative planning. This is especially true for patients whose biopsy tract is located on the lateral side.