Radiographs are late; MRI decides. Osteomyelitis is low T1 marrow signal CONFLUENT with a medullary pattern, contiguous with an ulcer or sinus tract — oedema alone, or a neuropathic joint, is not osteomyelitis.
Orient first
- Diabetic foot osteomyelitis spreads contiguously from an ulcer — the bone under the ulcer is the suspect bone.
- Charcot neuroarthropathy affects the midfoot joints, is peri-articular and subchondral, and usually has no ulcer; osteomyelitis is at pressure points (toes, metatarsal heads, calcaneus) under an ulcer.
- A radiograph cannot show marrow oedema; on MRI, T2/STIR oedema without T1 change is "osteitis" or reactive oedema, and confluent T1 marrow replacement is osteomyelitis.
Acquire the study
- Three views of the foot; comparison with prior films.
The manoeuvre
- Cortical destruction, periosteal reaction and loss of the cortical line under an ulcer — compare with the prior radiograph.
- Soft-tissue gas and foreign bodies on two views.
- Progression over 2 weeks on serial radiographs.
What confirms it
- Confluent T1 marrow replacement contiguous with an ulcer or sinus tract.
What licenses you to exclude it
- Normal T1 marrow signal makes osteomyelitis unlikely even with STIR oedema.
The classic misread
- Calling a normal radiograph a negative study — it lags by 10–14 days.