A 15-year-old boy was admitted to our hospital for a painful, swollen finger. There was no substantial medical history. Physical examination revealed a swollen proximal interphalangeal (PIP) joint of the fourth ray of the right hand. Further investigation revealed functional impairment, reduced flexion of the PIP segment. Plain radiography showed an expansile osteolytic lesion on the distal aspect of the proximal phalanx. Furthermore, intralesional septations were visualized (Fig. A). MRI demonstrated an expansile lesion with internal septations. T2 weighted MR images showed fluid-fluid levels and septations (Fig. B). After intravenous contrast administration an enhancing rim demarcating the lesion was seen (Fig. C, +C). Edema in the soft tissues surrounding the lesion was encountered, most likely indicating fracture (Fig. C, white arrows). The patient was treated with curettage resection with a good outcome.