• juvenile idiopathic arthritis
• ultrasonography
• disease activity

The use of musculoskeletal ultrasonography (US) in the management of rheumatoid arthritis (RA) has drawn attention to paediatric rheumatologists, and this has become an important part of the clinical care of patients with juvenile idiopathic arthritis (JIA) as well. However, several points have to be addressed before drawing conclusions on the usefulness in the everyday clinical management of JIA.

First, even in RA a similar viewpoint1 argued against the use of US for directing treatment decisions. In fact, many pitfalls have been highlighted by the authors, including the meaning of grey scale and/or power Doppler signal as sign of active inflammation versus past synovitis, the presence of abnormal US findings in a sizeable percentage of healthy subjects, the technical differences between different machines and the lack of standardisation. Indeed, the authors pointed out that in prospective therapeutic clinical trials with a Treat to Target (T2T) strategy following patients with US was not needed.

If we go to square one, it needs to be emphasised that in a growing skeleton the imaging results can be quite different than in adults. In fact, in children physiological US findings might be misinterpreted as pathologic. Skeletal maturation has a profound effect on imaging results, since bone, cartilage and adjacent structures undergo continuous modifications with growth. Normal US appearance of paediatric joints should be the starting point for any subsequent definition of pathology, and in particular for studies in JIA.

In order to standardise the use of US in paediatric rheumatology, definitions for US findings in the different parts of the normal paediatric joint have been developed and validated through Delphi process in different publications.2 3 A systematic standardised examination method was proposed, and an atlas of images of normal joint appearance at different ages has accordingly been created. Subsequently, the Outcome Measures …