Frontal radiograph of the right hip and CT scan of the hips on a different patient. Both reveal a cystic bubbly lesion with fine internal septations. Compromise of the cortical margin of the lesion is present as well. The “blister of bone” sign refers to a bubbly cystic lesion with a saccular protrusion of the cortex with multiple fine internal septae. The shell of the lesion may fracture resulting in extravasation of blood into the adjacent tissues. This sign is highly characteristic of aneurysmal bone cyst. | 
