Tenosynovial giant cell tumor (TGCT) is a rare, benign monoarticular disease that affects the synovial lining of joint, tendon or bursa. We distinguish two forms of the disease, localized and diffuse forms, both of which are histologically identical. The incidence rate of the localized form of TGCT (LTGCT) is 10 cases per million people, of which about 5% of all cases occur in the ankle. We present a rare case of LTGCT in the anterior part of the ankle in an adolescent, which was manifested by swelling and occasional pain, especially during sports activities. On the magnetic resonance imaging (MRI) a heterogeneously structured, well encapsulated tumor was visible in the anterior part of the ankle. In addition to the painless swelling in the anterior part of the ankle, the physical examination revealed a deficit of dorsiflexion of the foot. The operation was performed arthroscopically but the tumor could not be removed in a single piece due to its size, so it was removed in multiple pieces. Histopathological analysis confirmed that the tumor was TGCT. During the two-year follow-up period, the patient did not have problems with the operated ankle and no recurrence of the disease was observed on control MRIs. TGCT should be considered as a possible differential diagnosis, especially when pain and swelling of the ankle occur without injury. Arthroscopic surgery is a safe and effective method of treatment if it is performed by an experienced surgeon backed by a welltrained team. The choice of the type of surgical treatment should be determined depending on the anatomical position of the formation in the joint and the surgeon’s assessment and preference.

The goal of the study is to investigate posterior ankle impingement syndrome (PAIS) in the adolescent population and the differ- ences in delay periods for diagnosis. Furthermore, the intention is to present the results for arthroscopic treatment of PAIS in adoles- cents and compare them to the results found in published literature. A total of 16 adolescent patients (≤19 years old) included in the study were operated on solely for PAIS. A search was done on avail- able medical documentation primarily for the causes and length of the PAIS symptoms, and any reported complications. The Amer- ican Orthopaedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot score was used to evaluate ankle function, while patient satisfac- tion was measured using the Abdelatif questionnaire. The average age of the patients at the time of the procedure was 16.8 years. The median period from the appearance of the first symptoms until the diagnosis was 8.5 months. No perioperative complications were recorded in the median follow-up period of 75 months. An increase in AOFAS score was noted, ranging from an average of 70.9 preoperatively to 97.0 postoperatively. All of the patients were very satisfied with the results of the procedure, emphasizing postoperative improvement in everyday ankle use. This study confirms the presence of a diagnosis delay for PAIS in the adolescent population, which is in line with the results published in the literature. Additionally, it has been shown that arthroscopic surgery is highly efficient for treating PAIS in the adolescent popu- lation.