Musculoskeletal radiology tests - MRI

Role

MRI provides superior soft-tissue contrast for musculoskeletal imaging - detecting synovitis, bone marrow oedema, cartilage damage, and soft tissue pathology (tendon, ligament, muscle) earlier and more sensitively than X-ray, without ionising radiation
Increasingly used for early inflammatory arthritis diagnosis, where it detects synovitis and bone marrow oedema (a marker of active inflammation) well before the bony erosions visible on X-ray develop

Bone marrow oedema on MRI reflects active inflammation at the bone-synovium interface and is a recognised predictor of subsequent radiographic (X-ray-visible) erosion in inflammatory arthritis - detecting this earlier "pre-erosive" inflammatory stage is MRI's key advantage over plain X-ray for early disease

Particularly valuable for: early inflammatory arthritis (before X-ray changes are apparent), sacroiliac joint assessment in suspected axial spondyloarthritis (detecting active sacroiliitis via bone marrow oedema before X-ray-visible structural change), soft tissue/tendon pathology, and characterising indeterminate bone lesions
MRI of the sacroiliac joints showing active inflammation (bone marrow oedema) is now central to earlier diagnosis of axial spondyloarthritis, capturing disease at a "non-radiographic" stage that X-ray alone would miss

Contraindications/limitations: some older pacemakers/implants (most modern devices MRI-conditional), severe claustrophobia, longer acquisition time than CT/X-ray (motion artefact risk)
Findings of active inflammation on MRI can support earlier treatment initiation in inflammatory arthritis/spondyloarthritis, aligning with the broader shift toward treating before irreversible structural damage accrues

Early rheumatoid arthritis, non-radiographic axial spondyloarthritis, sacroiliitis, soft tissue/tendon injury, osteonecrosis (early detection)

MRI's ability to detect inflammation before structural (X-ray-visible) damage has occurred has genuinely changed diagnostic pathways in both RA and axial spondyloarthritis, enabling earlier diagnosis and treatment at a stage when damage may still be preventable

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