Brodie abscess is an intraosseous abscess related to a focus of subacute pyogenic osteomyelitis. It has a predilection for ends (metaphysis) of tubular bones: Proximal/distal tibial metaphysis (most common) Carpal and tarsal bones Rarely traversing the open growth plate; epiphysis (in children and infants). X-ray features: - Lytic lesion often in an oval configuration that is oriented along the long axis of the bone Surrounded by a thick dense rim of reactive sclerosis that fades imperceptibly into surrounding bone Periosteal new-bone formation +/- adjacent soft-tissue swelling MRI features: - The penumbra sign is a characteristic magnetic resonance (MR) feature of subacute osteomyelitis. It is seen as a discrete peripheral zone of marginally higher signal intensity than the central bony abscess cavity and the surrounding lower signal intensity of the reactive new bone and edema.