Basic imaging - X-ray of bone and joints

Role

Plain X-ray is the first-line imaging investigation for suspected bone/joint infection (osteomyelitis, septic arthritis) and trauma, though its sensitivity for early osteomyelitis is limited - radiographic changes typically lag clinical infection by 1-2 weeks, meaning a normal early film does not exclude the diagnosis
Widely available, low-cost, low-radiation-dose first investigation for any bone/joint symptom, but frequently needs to be followed by MRI when osteomyelitis is clinically suspected and the X-ray is normal or equivocal

Osteomyelitis produces periosteal reaction, cortical destruction, and sequestrum formation on X-ray - but these changes reflect bone remodelling that takes time to develop, explaining the delayed radiographic sensitivity relative to the earlier onset of clinical symptoms and MRI marrow oedema changes

Early osteomyelitis: X-ray often normal - MRI is far more sensitive at this stage and should be pursued if clinical suspicion is high
Septic arthritis: X-ray has limited diagnostic value for the joint itself (may show effusion or, late, joint space narrowing) - diagnosis rests on joint aspiration and synovial fluid analysis, not imaging alone
Serial/follow-up X-rays can track disease progression and response to treatment once a diagnosis is established

Normal X-ray with high clinical suspicion of osteomyelitis or septic arthritis -> proceed to MRI (osteomyelitis) or joint aspiration (septic arthritis) rather than being falsely reassured by a normal plain film
Confirmed changes -> guide surgical planning (debridement, sequestrectomy) alongside prolonged targeted antimicrobial therapy

Osteomyelitis (X-ray insensitivity in early disease), septic arthritis (aspiration-dependent diagnosis, not imaging-dependent), diabetic foot infection (X-ray for bone involvement assessment)

A normal plain X-ray early in a suspected bone or joint infection is expected and does not exclude the diagnosis - radiographic changes in osteomyelitis lag clinical disease by 1-2 weeks, and septic arthritis diagnosis rests on synovial fluid analysis rather than imaging findings at all

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