Paediatric and Adolescent Rheumatology [143–150]: 143. Knee Joint in JIA: A Prospective Evaluation of Clinical Examination, Ultrasound and Mri Assessment. A Newly Developed Knee MRI Scoring System in JIA

Abstract

Background: We prospectively compared agreement between clinical, ultrasound (US) and MRI assessments of the knee joints in children with juvenile idiopathic arthritis (JIA).

Methods: Three hundred and thirty one knees from 48 children over a period of 2 years, affected by JIA with knee arthritis, were assessed clinically and ultrasonographically on the same day, using a semi-quantitative scoring system from 0 to 3 (0: normal; 1: mild; 2: moderate; 3: marked) for swelling and effusion, respectively. A subgroup of these children (25) with a total of 40 knees had matching MRI scans obtained within 0 to 14 days from clinical and US examinations. For those, US and MRI scans (T1 weighted images) were scored 0-3 for effusion, synovial hypertrophy, bone oedema and bone erosions, using for the first time our newly developed knee MRI scoring system.

Results: A moderate agreement for effusion was found between the 331 knees assessed clinically and ultrasonographically (linear weighted Kappa: 0.54). Out of the 260 clinical normal knees, 30 (11.5%) had mild to moderate effusion on US and 89 (34.2%) had trace of effusion. In the subgroup of 40 knees that had matching US and MRI scans it was demonstrated a good agreement for effusion (linear weighted Kappa: 0.66) and a moderate agreement for synovial hypertrophy (linear weighted Kappa: 0.47). The inter-observer US agreement was very good for effusion (linear weighted kappa: 0.87) and good for synovial hypertrophy (linear weighted kappa: 0.68). The intra-observer MRI agreement was good for effusion (linear weighted kappa: 0.73) and very good for synovial hypertrophy (linear weighted kappa: 0.85).

Conclusions: A significant number of knee joint effusions are missed on clinical examination. Musculoskeletal US is a simple, cheap, non invasive, rapid and effective method of detecting joint synovitis in JIA and should be used: as an adjunct to clinical examination especially when joint injections are being considered and to avoid under-diagnosis; when clinical examination is negative and symptoms are equivocal for active arthritis; to identify the site for the intra-articular injection; at follow-up to assess treatment’s efficacy. In our experience it is also very well tolerated by children. Normal data on Paediatric knees are needed to demonstrate whether a small amount of synovial fluid is present.

Comparison between clinical and US scores (0-3) for swelling and effusion respectively

US EFFUSION SCORE	CLINICAL	SWELLING	SCORE
	0	1	2	3
0	230	5	0	0
1	25	27	7	0
2	5	2	12	8
3	0	0	3	7

Disclosure statement: All authors have declared no conflicts of interest.