57-year-old man with diabetes.  Sagittal STIR image (A) demonstrates shallow ulcer over the calcaneal tuberosity with underlying subtle inflammation of the cortex consistent with osteitis and early osteomyelitis.  Follow-up sagittal STIR (B) and T1 (C) weighted images obtained 4 months later demonstrate marked progression of osteomyelitis.  Note gas and pus in sinus tract in overlying soft tissues. (Click on the images to see larger versions)