A 20-year-old male presented to the OPD with a deep boring pain in the upper end of left tibia which worsened at night/while walking and is relieved by rest. On examination, there is effusion in the knee joint along with tenderness and thickening of the bone. X-ray of the concerned area was taken. MRI of the concerned area was also done.

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.