Synopsis
Select musculoskeletal imaging by the clinical question, understand what radiography, ultrasound and MRI can and cannot establish, and integrate findings without delaying urgent aspiration, referral or treatment.
- Begin with a question such as fracture, structural damage, active synovitis, tendon tear, sacroiliitis or spinal compression; 'pain' alone is not an imaging indication.
- Plain radiography shows alignment, fracture, osteophytes, joint-space loss, erosions, periosteal change and mineralisation but is relatively insensitive to early soft-tissue inflammation.
- Ultrasound provides dynamic assessment of accessible synovium, effusions, tendons, entheses and Doppler vascularity and can guide aspiration or injection.
- Ultrasound is operator- and site-dependent; a negative study does not exclude deep-joint, axial or intermittent disease.
- MRI detects marrow, cartilage, synovial, tendon, sacroiliac and neural pathology with high sensitivity, but many abnormalities occur in asymptomatic people.
- In suspected axial spondyloarthritis, follow the NICE sequence and specialist imaging protocol; a normal radiograph does not exclude non-radiographic disease.
- Radiographic osteoarthritis severity correlates imperfectly with pain and should not displace examination, function and patient goals.
- Before MRI check implants, metallic foreign bodies, pregnancy and ability to tolerate the scan; before ionising imaging justify exposure and use previous studies.
Key red flags
Cord, cauda equina or rapidly progressive focal neurological features require emergency MRI through the acute pathway, not routine rheumatology booking.
Investigation priorities
Assess fracture, alignment, structural arthropathy, calcification and established inflammatory damage.
Management branches
Possible infection, unstable fracture, compartment syndrome or neurological compression.
- Stabilise the patient and perform focused neurovascular examination, obtaining the fastest appropriate radiograph, ultrasound or MRI through the emergency pathway.
- Use ultrasound for urgent aspiration when helpful, but take cultures and begin indicated antimicrobial or surgical treatment without waiting for elective cross-sectional imaging.
- Communicate the exact threatened structure and repeat examination during transfer or delay so deterioration triggers immediate escalation.