The earliest features of osteomyelitis are seen on MRI, manifesting as bone marrow edema, which can be seen in as little as 24-48 hours from the onset of infection. This is at a time where the only plain film findings would be surrounding soft-tissue swelling. Even nuclear medicine bone scans take a few days before showing increased uptake. Later on as time progresses, sclerosis and/or lucency and periosteal reaction may be evident on plain films, at which time MR demonstrates more well-defined edema, bone abscesses (Brodie abscess) with peripheral contrast enhancement, and similar findings in the soft-tissues. The hallmarks of chronicity are bony sequestra (dead bone) within an involucrum (essentially a cavity), cloaca (cortical break in involucrum allowing for decompression into the soft-tissues), and sinus tracts. A sequestrum may be seen on plain films, CT, and MRI.