BACKGROUND: The mediopatellar synovial fold (MPSF) of the knee joint is normally a thin and elastic structure, but under the influence of various factors, the MPSF thickens and turns into a fibrous cord, which injures nearby structures and clinically manifests with pain. One of the effective methods of treating MPSF in pediatric patients is an arthroscopic excision of the fold. AIM: Evaluation of long-term results of arthroscopic treatment of patients with pathologically thickened MPSF of the knee joint. MATERIALS AND METHODS: There was conducted an analysis of primary medical documentation, which included the study of hospital records and case histories of 73 patients. The survey questionnaires (based on VAS and WOMAC scales) were sent to these patients. Responses were received from 35 patients who were included in the study. RESULTS: When evaluating the long-term results of surgical intervention in 35 operated patients in 29 (82.1%) patients, it was found out that there were no exacerbations in postoperative period and, at the time of the data collecting, there weer no complaints for the pain syndrome. Dysplasia of the femoral condyle of type A and B was diagnosed in these patients. At the time of the evaluation, 6 (18.9%) patients had pain syndrome with decreased function of the knee joint. In these patients, dysplasia of the femoral condyle corresponded to type C in 4 cases, types D and B in 1 case. CONCLUSION: At the early stages of the disease, it is necessary to carry out a detailed differential diagnosis to identify the pathology of the knee joint. Attention should be paid to the combination of a pathologically thickened MPSS with dysplasia of the femoral condyle, which can lead not only to complications of conservative therapy and ineffectiveness of surgery, but also to the development of patellofemoral arthrosis.