Synovial thickening and effusion with Doppler signal (ultrasound) or synovial enhancement (MRI) in a child with persistent arthritis; the child's cartilage is thick and unossified, so erosions and growth disturbance are judged against age norms.
Orient first
- Arthritis for over 6 weeks under 16 years of age; oligoarticular, polyarticular and systemic subtypes.
- Temporomandibular joints are often involved silently — MRI finds it.
- Normal paediatric synovium and physes can show Doppler signal — know the normal vessels.
Acquire the study
- Joint ultrasound with high-frequency linear probe and power Doppler; contrast-enhanced MRI of the index joint (and TMJs).
The manoeuvre
- Effusion depth in mm in the joint recess compared with the contralateral side.
- Synovial hypertrophy (non-compressible hypoechoic tissue) and power Doppler signal within it.
- Tenosynovitis; cartilage thickness and surface.
What confirms it
- Clinical diagnosis supported by imaging synovitis; other causes (infection, malignancy) excluded.
What licenses you to exclude it
- No effusion, synovial thickening or enhancement in a symptomatic joint argues against active arthritis at that joint.
The classic misread
- Calling normal epiphyseal vessels synovial hyperaemia.
- Missing leukaemia presenting with joint pain — look at the marrow.