Primary epiphyseal aneurysmal bone cyst with an unusual presentation

A 12-year-old female child presented with knee pain and restricted range of motion (ROM). Investigations revealed a bony lytic lesion confined to the epiphysis, which was found to be an aneurysmal bone cyst (ABC) on histopathologic examination. She underwent open curettage, and the cavity was filled with bone graft substitute. On long-term follow-up, the child had a good ROM with resolution of pain and a normal gait, with mild leg length discrepancy. Primary epiphyseal ABCs are rarely reported in the literature, but this case serves as a reminder to keep this entity in the differentials while dealing with such patients.