Clinical Presentation

A 16-year-old boy with pain after twisting his knee.

(A,B) Anteroposterior and lateral radiographs: There is a lucent lesion in the posteromedial cortex of the tibia with a thin, scalloped sclerotic border (arrows). There is no associated periostitis.

Differential Diagnosis

• Nonossifying fibroma (NOF): A blister-like lesion in the cortex of the metaphysis of a long bone with a thin sclerotic border in a patient who is younger than 30 years old is most likely an NOF. There should be no periositis or pain (unless a pathologic fracture is present).

• Aneurysmal bone cyst: Should be more expansile and may have periostitis. The patient typically presents because of pain.