Which imaging study is best for diagnosing osteomyelitis?

• A. X-ray
• B. CT
• C. Ultrasound
• D. MRI

Answer: (D)

Osteomyelitis starts in the bone marrow, so the most informative imaging looks for marrow changes. MRI excels here because it detects bone marrow edema and inflammation very early, often within days of infection, and it can show the full extent of disease in both bone and surrounding soft tissues. This makes MRI the most sensitive and reliable test for diagnosing osteomyelitis and for guiding treatment, including identifying any abscesses or soft tissue involvement.

X-ray often misses early disease because bone changes aren’t visible until later, after weeks. CT provides excellent detail of the cortical bone and can identify sequestra, but it’s less sensitive to early marrow changes and involves radiation. Ultrasound is useful for evaluating surrounding soft tissues or guiding drainage but doesn’t reliably visualize bone inflammation itself.