REVIEW Open Access

Ultrasound in juvenile idiopathic arthritisSilvia Magni-Manzoni

Abstract

Background: In the recent years, musculoskeletal ultrasound (MSUS) has been regarded as especially promising inthe assessment of juvenile idiopathic arthritis (JIA), as a reliable method to precisely document and monitor thesynovial inflammation process.

Main content: MSUS is particularly suited for examination of joints in children due to several advantages overother imaging modalities. Some challenges should be considered for correct interpretation of MSUS findings inchildren, due to the peculiar features of the growing skeleton. MSUS in JIA is considered particularly useful for itsability to detect subclinical synovitis, to improve the classification of patients in JIA subtypes, for the definition ofremission, as guidance to intraarticular corticosteroid injections and for capturing early articular damage. Currentevidence and applications of MSUS in JIA are documented by several authors. Recent advances and insights intofurther investigations on MSUS in healthy children and in JIA patients are presented and discussed in the presentreview.

Conclusions: MSUS shows great promise in the assessment and management of children with JIA. Nonetheless,anatomical knowledge of sonographic changes over time, underlying immunopathophysiology, standardizationand validation of MSUS in healthy children and in patients with JIA are still under investigation. Further researchand educational efforts are required for expanding this imaging modality to more clinicians in their daily practice.

Keywords: Musculoskeletal ultrasound, Juvenile idiopathic arthritis, Children, Pediatric rheumatology

BackgroundJuvenile idiopathic arthritis (JIA) is the most commonchronic rheumatic disease of childhood and an import-ant cause of acquired disability in children [1]. Despitethe heterogeneity, all forms of JIA are characterized byprolonged synovial inflammation that can cause cartil-age and bone damage, with severe impairment of phys-ical function and impact on the quality of life. In therecent years, the availability of powerful and expensivedrugs increased the need to identify patients with ahigh likelihood of developing erosive damage early andpatients with a less aggressive disease, so as to institutethe appropriate therapy at and for the most convenienttime. This induced to search for sensitive methods forreliable documentation and precise monitoring of thesynovial inflammation process [2–4]. Musculoskeletalultrasound (MSUS) demonstrated to be a valid andreliable tool in the assessment of chronic inflammatoryarthropathies in adults [5–7]. Therefore, it has been

regarded as especially promising in the assessment ofjoints in children with JIA [8–11].

Advantages of MSUS in childrenThough MSUS has some limitations, it is particularlysuited for use in children for several advantages overother imaging techniques (Table 1). It is quick, it doesnot expose the child to ionizing radiation, it does notrequire sedation or general anesthesia, it allows formultisite assessment in the same session, comparisonbetween symptomatic and asymptomatic sites, dynamicstudy, and it is easily repeatable. Moreover, it is wellaccepted by both children and their parents, and it isthe only imaging technique that can be coupled withthe conventional approach to patient assessment in theclinic (Fig. 1).

Challenges with MSUS in childrenLike other imaging modalities, MSUS is an operatordependent imaging technique. Further, it is highlydependent on the properties and sensitivity of themachine used, which can range widely (Fig. 2). As in

Correspondence: silvia.magnimanzoni@opbg.netPediatric Rheumatology Unit, IRCCS Ospedale Pediatrico Bambino Gesù,Piazza Sant’Onofrio 4, 00165 Rome, Italy

© 2016 The Author(s). Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, andreproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link tothe Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver(http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Magni-Manzoni Pediatric Rheumatology (2016) 14:33 DOI 10.1186/s12969-016-0096-2

adults, MSUS in children requires continuous practiceafter appropriate training and has a limited value insome musculoskeletal areas, such as the axial skeleton.When dealing with musculoskeletal imaging in child-

hood, it is noteworthy to emphasize the unique feature ofthe growing skeleton, which include age-related variationof the thickness of the articular cartilage and incompleteossification. Moreover, in children the epiphysis are vascu-larized and metaphyseal vessels anastomose with epiphys-eal vessels through the growth plate. Depending on the

properties and sensitivity of the ultrasound machine,vascularization in this area can be physiologically detectedby MSUS in healthy children [12], whereas it would beregarded as pathological in adults. Several pitfalls can leadthe ultrasonographer with little experience in pediatricjoints to embarrassing misinterpretation of images (Fig. 3).Therefore, the awareness of a high ratio cartilage/bone,that changes during child growth, and the anatomicalknowledge of the feeding vessels are of foremost value andcannot be overtaken.

Table 1 Advantages and limitations of musculoskeletal ultrasound (MSUS) compared to magnetic resonance imaging (MRI) andconventional radiology in children with juvenile idiopathic arthritis

Imaging modality Advantages Limitations

MSUS Lack of exposure to ionizing radiationRapidity of performanceEase of repeatabilityHigh patient acceptabilityDemonstration of soft tissue inflammationDirect visualization of cartilageEarly detection of bone erosionsAbility to scan multiple joints in a single sessionSupport in guidance of procedures (e.g. intra- articularcorticosteroid injections)Relatively inexpensive

Difficulties in carrying out in case of severe joint limitationRelatively small field of viewInability to assess the whole joint spaceAcoustic shadowing from overlying bonesLimited value in the assessment of axial skeleton andtemporomadibular jointsDependency on the properties and sensitivity of theultrasound equipmentNeed of continuous practice after appropriate trainingReliability, standardization and validation in children underinvestigation

MRI Lack of exposure to ionizing radiationMultiplanar tomographical imagingAbility to assess the whole joint spaceDemonstration of soft tissue inflammationDirect visualization of cartilageEarly detection of bone erosionsVisualization of bone marrow oedemaHigh tissue contrastSuitable for assessment of axial skeleton and temporomadibularjoints

Intravenous contrast agent often requiredPossible allergic reaction to contrast agentsGeneral anesthesia required in younger childrenLong examination timeEvaluation limited to one target jointReliability, standardization and validation in children underinvestigationHigh costVariable availability worldwide

Conventionalradiology

Rapidity of performanceApplicability to all jointsDemonstration of joint space narrowing, disturbances of bonegrowth and maturationDetection of bone erosionsValidated scoring methods in childrenSuitable for longitudinal evaluation of damage progressionLow costWidespread availability

Exposure to ionizing radiationsInability to directly visualize cartilage and soft tissueinflammationLate detection of bone erosions and joint space narrowingProjectional superimposition

Fig. 1 MSUS is well accepted by children and their parents, and can be performed as completion of the joint examination during the standardclinical assessment of the child. Some children have fun during MSUS evaluation, others totally relax and can fall asleep

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Usefulness of MSUS in childrenDespite several challenges, MSUS is commonly regardedas a very useful tool in children, as outlined by the re-sults of recent national and international surveys amongpediatric rheumatologists [13, 14]. For most of the re-spondents, MSUS owned particular relevance for theability to detect subclinical synovitis and to improve theclassification of patients in JIA subtypes, as guidance tointraarticular corticosteroid injections and for capturingearly articular damage. In addition, some specific jointswere considered as most suited to be studied by MSUS,specifically the midfoot, the ankle, the hip, the wrist, thesmall joints of hands and feet.

What is the evidence for usefulness of MSUS in JIA?Subclinical synovitis and tenosynovitisArthritis in JIA is so far defined as swelling within ajoint, or limitation in the range of joint movement withjoint pain or tenderness, persistent over time, observedby a physician, and not due to primarily mechanical

disorders or to other identifiable causes [15]. Currently,the definition of an oligoarticular or polyarticular involve-ment is based on the number of active joints. Therefore,complete joint assessment is mandatory for accurate as-sessment of the disease. However, in the recent years sev-eral authors documented a discrepancy between clinicaland MSUS examination in detecting synovitis in JIA. Inour experience, 1664 joints in 32 children with JIA wereevaluated both clinically and with MSUS. A total of 104(6.3 %) and 167 (10 %) joints had clinical and MSUS syno-vitis, respectively. Of the 1560 clinically normal joints, 86(5.5 %) had synovitis on MSUS. The frequency of subclin-ical synovitis was greater in wrists, PIP, subtalar and footjoints [16]. Haslam et al. compared clinical and MSUSevaluation in 680 joints of 17 patients with early(<12 months) oligoarticular JIA. Six children had subclin-ical synovitis, more frequently detected in the small jointsof hands and feet [17]. Other authors reported similarfindings in the assessment of peripheral joints and theankle [18–20]. In particular, Rooney at al. observed thatthe clinical examination might not be able to distinguishwhether joint swelling in the ankle is due to synovitis,tenosynovitis or both (Fig. 4). In 34 JIA patients who hadclinically detected swelling in 49 ankles they evaluated theprevalence of MSUS synovitis and tenosynovitis. Only29 % of ankles had tibiotalar effusion alone, whereas teno-synovitis associated with tibiotalar synovitis and tenosyno-vitis alone were detected in 71 and 39 % of ankles,respectively. Concomitant tenosynovitis and tibiotalar ef-fusion were found in 33 % of ankles [20]. In another studyof the same group, 32 % of the ankles considered clinicallyinvolved did not show MSUS synovitis. In 42 % of anklesrecorded as clinically normal MSUS detected involvementof medial tendons, whereas less than 50 % of the lateraltendons deemed to be clinically involved were affected onMSUS [21].These findings highlight that clinical examination in

JIA may underestimate the extension of synovitis andsometimes cannot be precise, whereas MSUS can im-prove the sensitivity and the accuracy in the detection ofthe exact sites of inflammation in the joint. Therefore,implementation of clinical examination with MSUS inchildren with JIA can lead to important implications intherapeutic decisions (i.e. indication to a second linedrug or biologic treatment, or exact location of intraarti-cular corticosteroid injections) and for monitoring treat-ment efficacy.

EnthesitisEnthesitis represents the main feature of the enthesitis-related arthritis (ERA) JIA subgroup, according tothe International League of Associations for Rheumatol-ogy (ILAR) classification of JIA, and is clinically definedas tenderness at the insertion of a tendon, ligament, joint

Fig. 2 Longitudinal scan of the suprapatellar recess in two 7 yearsold boys performed with high multifrequency probe: a. Top-levelultrasound machine in the early 2000’s; b. Top-level ultrasoundmachine in 2015

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Fig. 4 A 10 years old girl with JIA presented with mild swelling of the left ankle, without tenderness/pain on motion or limitation on motion.MSUS showed no signs of synovitis at the tibiotalar joint (a), and allowed detection of a hypo-anechoic halo around the medial tendons (b) andpathologic vascularization on power Doppler along both the posterior tibialis tendon (c) and the common flexor digiti tendon (d), indicatingflourishing tenosynovitis. PTT: posterior tibialis tendon; CDT: common flexor digitorum tendon; A: posterior tibialis artery; V: posterior tibialis vein

Fig. 3 Metaphysis (M) look like erosions; epiphysis (E) and unossified bones are anechoic, like synovial effusion (a,b). Physiological vascularization atinsertion of enthesis to the cartilage can be frequently detected, resembling enthesitis (c). Feeding vessels can be intraarticular or close to ossifyingnuclei, and must not be considered as signs of active synovitis (d). a. Dorsal longitudinal scan of the II metacarpophalangeal joint in a 2 years old child,grey-scale. b. Longitudinal medial scan of the suprapatellar recess in a 2 years old child, grey-scale. c. Longitudinal scan of the Achilles tendon at insertionto the calcaneus in a 5 years old child, power Doppler d. Longitudinal medial scan of the suprapatellar recess in a 5 years old child, power Doppler

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capsule, or fascia to bone [15]. The clinical demonstra-tion of enthesitis in children is challenging owing to thepeculiar fat distribution, that can mask the anatomicallandmarks, and the frequently insufficient cooperation ofvery young children. A recent study reported on MSUSsensitivity to detect enthesitis in children with JIA [22].The authors compared physical examination and powerDoppler (PD) MSUS in detecting enthesitis in five sites(the quadriceps tendon insertion, the proximal and thedistal patellar ligament insertion on the tibial tuberosity,the Achilles tendon insertion on the posterior surface ofthe calcaneus, and the plantar fascia insertion) in 26 pa-tients with JIA and 41 healthy children. None of thehealthy children had PD MSUS evidence of enthesitis. Inpatients with JIA physical examination showed enthesitisat only 12.5 % of sites, whereas PD MSUS enthesitis wasfound at 9.4 % of the investigated sites. Clinical enthesi-tis was often associated with PD MSUS enthesitis. Onthe other hand, 50 % of the sites exhibiting PD MSUSwere clinically normal. Of note, 20 % of the sites withPD MSUS enthesitis were in patients with oligoarticularJIA and 10 % in patients with polyarticular JIA.Recent studies confirmed a higher sensitivity of MSUS

in comparison with clinical examination in detectingenthesitis in different entheseal sites in patients withERA-JIA [23, 24].These findings overall indicate that MSUS may help

to detect clinically silent peripheral enthesitis in ERAand non-ERA patients, and can contribute substantiallyto the correct diagnosis and classification of JIA. Onthe other hand, comprehensive knowledge of the ultra-sonographic appearance of entheses in healthy subjectsduring the developmental ages is still under investiga-tion (Fig. 5) and reliable definitions for normal andpathological MSUS findings in pediatric entheses needfirst to be addressed.

ILAR classification JIA subgroupsThe most recent ILAR classification criteria for JIA weredeveloped to delineate homogeneous subtypes of JIA forresearch purposes [15] and so far have been adopted tostratify patients and select candidates to second-linetreatment or biologic therapy [25–31]. In particular, chil-dren with JIA are classified as having oligoarthritis orpolyarthritis based on the number of affected joints; thepresence of active arthritis in at least five joints is arequisite for the definition of a polyarticular diseasecourse and for the eligibility to second-line or biologicagents in several health systems. As already mentioned,MSUS demonstrates higher sensitivity in detecting syno-vitis than the clinical examination, and, as a conse-quence, can lead to reclassify patients, with a trendtowards a more extensive joint involvement and poten-tial more aggressive therapy. In the author’s experience,

of 32 children with JIA evaluated cross-sectionally bothwith clinical and MSUS examinations, five patients, clas-sified as having mono/oligoarthritis involvement by clin-ical examination, showed a polyarthritis involvementbased on MSUS findings [16]. Similarly, one patient outof 17 children with oligoarticular JIA was reclassified ashaving polyarthritis after MSUS examination by Haslamet al. [17]. Of note, MSUS could precisely identify in-flammatory tendon involvement in JIA patients withankle arthritis, as outlined by Rooney at al [20, 21].Though tendons can be affected throughout the wholecourse of JIA, the current ILAR classification does nottake into consideration tendon involvement. Further,MSUS enthesitis could be found in both in ERA andnon-ERA-JIA patients, as mentioned above [22–24].Overall these findings suggest that the use of MSUS

may yield important insights in the location of inflam-matory changes in joints and in different JIA subtypes,providing the anatomic rationale for a future refinementof the classification of childhood arthritis.

Definition of disease remissionIt has been recently argued that remission of JIA definedon clinical grounds does not couple with remission definedwith imaging [32–34]. However, the clinical significance

Fig. 5 Sonographic appearance of the patellar enthesis at differentages. a. 2 years old girl; b. 8 years old girl; c. 10 years old boy. DPT:distal patellar tendon

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and prognostic value of this finding is unclear, as thepresence of MSUS abnormalities, including PD signal,in patients with clinically defined inactive disease didnot predict subsequent synovitis flare [35]. This findingcontrasts with observations in adults with rheumatoidarthritis (RA), in which vascularization detected by PDMSUS predicted shortterm disease flare after clinicalremission [36, 37].These puzzling MSUS features may be due to under-

lying immunopathological mechanism and local changespeculiar of JIA, still unknown and different to the clas-sical autoinflammatory process in seropositive RA [38].Future research oriented to explore this supposition andcorrelation of MSUS with biologic markers of disease ac-tivity [39, 40] is advisable.

Imaging guided injectionsIntra-articular corticosteroid injections (IACI) are widelyused in JIA to induce prompt relief of symptoms of ac-tive synovitis. Blind-method is sometimes difficult in theyounger, due to the small joint size and the subcutane-ous fat masking bony landmarks. Therefore MSUS mayrepresent a fundamental tool, not only for the precisedetection of the inflamed area, but also for the accurateplacement of the needle tip within the different affectedanatomical structures, in order to maximize the treat-ment efficacy and minimize local side effects (mainlysubcutaneous atrophy or local skin hypopigmentation)[41] (Fig. 6). Several authors documented the correctneedle placement and the efficacy of MSUS-guided in-jections of clinically difficult to access joints, such as thehip [42], or clinically difficult to assess joints, such asthe ankle and the midfoot [43]. In particular, Laurell atal. performed MSUS-guided IACI in 85 compartmentsof the ankle, including twenty-one tendon sheaths and aganglion cyst, and observed normalization or regressionof MSUS-detected synovial hypertrophy in 89 % of theinjected sites at 4 weeks after IACI. The same authorsalso reported on the efficacy of MSUS-guided IACI in21 compartments of 15 wrists, with increasing improve-ment of synovial hypertrophy and synovial hyperemia at1 week and 4 weeks post-injection [44]. Another jointthat can particularly benefit from MSUS-guided IACI isthe temporomadibular joint (TMJ). Efficacy and safetyassessed 6–8 weeks post MSUS-guided injection of 63TMJ in 39 children with JIA showed improvement in allsymptoms and only one side effect (local scar) in one pa-tient [45]. However, data on correct needle placement inTMJ by MSUS-guidance are scarce and controversial[46, 47], and need to be further investigated.

Cartilage damageJoint cartilage is a known target in inflammatory arth-ritis. Though MSUS do not allow to visualizing cartilage

in its entireness in all joints, due to its limited acousticwindow, loss of MSUS detected cartilage in “key sites” ofthe joints may represent an early marker of damage inJIA. Spannow, et al were the first to attempt the meas-urement and quantification of cartilage thickness inpediatric subjects [48]. They provided normal ranges ofMSUS-detected cartilage thickness in small and largejoints of healthy children, and designed a complicatedformula in order to calculate cartilage thickness in theclinically dominant joints for different age groups ofchildren [49]. Cartilage was found significantly thicker inboys than in girls and diminished progressively with agein both sexes, as similarly reported later by other authors[50]. The same investigators provided data on intra- andinterobserver agreement and validated MSUS measure-ment of cartilage thickness in several joints of healthychildren by comparing MSUS with findings obtainedwith magnetic resonance imaging (MRI), with an overallgood agreement except for the wrist [51, 52]. In a subse-quent study, Spannow and coworkers measured cartilagethickness with MSUS in joints of patients with JIA, andcompared the findings with those obtained in healthychildren. Of note, cartilage thickness in joints of patients

Fig. 6 MSUS allows detection of the exact location of inflammationand correct needle placement, even in very small sites, such as thesynovial sheath of the flexor tendon of the VI digit in a 3 years oldgirl. NT: needle tip; FDT: flexor digiti tendon; SE: synovial effusion

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with JIA was significantly lower than in the healthy cohort,regardless of whether the examined joints have been pre-viously affected by arthritis [53]. Pradsgaard, et al. fromthe same group of investigators, compared MSUS andMRI measurements of distal femoral cartilage thickness inchildren with JIA. They identified the intercondylar notchas the best site to assess cartilage thickness, because of itseasier assessment and lower variability on MSUS as com-pared to MRI [54]. These findings may support that irre-versible changes can occur in cartilage of children withJIA despite the localization of synovial inflammation. Themeasurement of cartilage thickness at the intercondylarnotch of the knee may act as a surrogate of overall earlycartilage damage in JIA patients. However, since MSUSand MRI cartilage measurements at different sites of theknee were problematic in the previously affected andunaffected knees compared to the whole cohort, this pro-posal is controversial [55]. Thorough studies in patientswith long term inactive and active JIA and comparison withthe newer MRI techniques for the biochemical evaluationof cartilage matrix composition over time [56] would giveinsights to address these challenging issues.

Bone erosionsCompared with conventional radiography, the capacityto assess dynamically and in real-time the joints in sev-eral planes makes MSUS a more useful tool for detectingerosions [57, 58]. The OMERACT (Outcome Measuresin Rheumatology Clinical Trials) definitions of bone ero-sion require documenting an interruption of the intraar-ticular bone surface or cortical breaks with a step-offbone defect visible in at least two perpendicular planes[59]. However, children anatomy is characterized byphysiological bone irregularities due to the presence ofossification centers and growth plates at the epiphysealcartilage. Moreover, when ossified, some bones can atfirst appear fragmented and irregular (Fig. 7). Conse-quently, in children all these peculiar normal findingsmay potentially be misinterpreted as cortical erosions byinexperienced operator eyes. Further, due to the peculiarvascularization of the epiphysis in children, that anasto-moses with metaphyseal vessels through the growthplate, an inflammation affecting the epiphyseal cartilagemay spread to the ossification center, causing excessivegrowth, deformities, or destruction with epiphyseal ero-sions rather than marginal erosions, unlike RA patients.These observations advise that further validation andlarge-scale studies are required to determine the poten-tial role and the accuracy of MSUS in the detection ofbone damage in children.

Advances and perspectivesAt present, increasing interest in the use of MSUS dur-ing daily clinical practice is spreading among pediatric

rheumatologists. Nonetheless, several topics are stillunder investigation or need to be further addressed.First of all, the anatomical specificities of the growingskeleton in children make imaging interpretation morechallenging than in adults and thorough knowledge ofthe sonoanatomy changes at the different growth agesis essential to distinguish physiological appearance frompathological findings. Recently, definitions for grayscale sonographic features of joints in healthy childrenhave been proposed and validated [60]. Sonographic ap-pearance of tendons, entheses and Doppler MSUS inhealthy children was not described and requires specificadditional studies. Secondly, in the recent years severalinvestigators proposed to assess children using standardscans according to the EULAR (European League AgainstRheumatism) guidelines [61]. However, this scanningapproach has been developed for MSUS examination ofadults, and its applicability and reliability in childrenwere not demonstrated. In the frame of the OMERACTUltrasound pediatric subtask force, Collado et al. set up

Fig. 7 The calcaneus bone appears fragmented in childrenrespectively aged 6 years (a), 8 years (b), and 10 years (c). Feedingvessels can be detected by power Doppler (red dots)

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a standardized MSUS examination method specific forthe pediatric population [12]. The study showed a highquality of images obtained by all the investigators, des-pite the use of different sonographic equipments, indi-cating suited methodology. MSUS standard scansproposed were appropriate and reproducible in childrenregardless of their age. Further, the standardized MSUSexamination, together with the MSUS definitions ofnormal features in pediatric joints, enabled the investi-gators to achieve information on physiological bloodflow and on age-related changes of bones in each joint.The next step would be standardization of findings insynovitis and in abnormal vascularization detected byDoppler, and is already ongoing.Studies in adults with RA have recommended the use

of reduced and simplified joint counts for MSUS as-sessment of disease activity, preventing in this way toolong-lasting evaluations [62, 63]. This may be particu-larly relevant in children, since they notoriously are lesstolerant than adults of undergoing investigations. Re-cently, some investigators proposed a reduced joint PDMSUS assessment and provided preliminary evidenceof its validity, reliability, sensitivity to change and feasi-bility in evaluating synovitis in JIA [64]. Nonetheless,these results should be confirmed in independent co-horts with large number of patients. Additional studiesin children with JIA in order to define the pattern andnumber of joints to be assessed with MSUS, both withgrey scale and Doppler, are warranted.Although there is an astounding interest in the appli-

cation of MSUS in children, only few pediatric rheuma-tologists are able to perform MSUS on their own, asoutlined by recent surveys [13, 14]. On the other hand,most of the respondents to the surveys stated their will-ingness to embrace this imaging modality and to gainexperience in performing MSUS by themselves. There-fore, access to suitable training and mentorship forMSUS in children is of primary relevance. Further edu-cational activities are required to enhance the use of thisimaging modality in pediatric rheumatologists’ practice.

ConclusionsMSUS shows great promise in the assessment and man-agement of children with JIA, so that it is likely to playan increasing role in clinical practice of pediatric rheu-matologists, as in adult rheumatology. However, severalissues, including the anatomical knowledge of sono-graphic changes over time and the underlying immuno-pathophysiology, the standardization and validation ofMSUS in healthy children and in patients with JIA, arestill under investigation. Currently, few pediatric rheu-matologists are able to perform MSUS on their own. Inthe future further research and educational efforts are

required for expanding this imaging modality to moreclinicians in their daily practice.

Key points

� MSUS can detect inflammatory changes morefrequently than the clinical examination and canvisualize their exact location in joints of childrenwith different JIA ILAR subtypes, yielding importantinsights in the extent, pathophysiology andclassification of childhood arthritis.

� Due to the unique features of the growing skeleton,accurate knowledge of MSUS findings over time inchildren is warranted. Currently, validateddefinitions of MSUS features in joints of healthychildren are available; standardization of scanningtechniques specific for the pediatric population anddefinitions of MSUS pathological findings inchildren are ongoing.

� Correlation of MSUS findings with biologic markers,clinical features and other imaging tools should bestudied prospectively to investigate the clinicalmeaning and prognostic value of MSUS-detectedabnormalities in different joints at different timepoints of the disease course.

� Despite the astounding interest in the use of MSUSin children, only few pediatric rheumatologistscurrently perform MSUS on their own. Furthereducational activities for suitable training andmentorship in MSUS in children are advisable inthe future.

AbbreviationsMSUS, musculoskeletal ultrasound; JIA, juvenile idiopathic arthritis; ERA,enthesitis-related-arthritis; PD, power Doppler; ILAR, International League ofAssociations for Rheumatology; RA, rheumatoid arthritis; IACI, intraarticularcorticosteroid injection(s); TMJ, temporo-mandibular joint(s); MRI, magneticresonance imaging; OMERACT, Outcome Measures in Rheumatology ClinicalTrials; EULAR, European League Against Rheumatism.

AcknowledgementsThe author is grateful to the patients' guardians/parents for their consent toinclude images in the present review.

FundingNo funding supported the review.

Availability of data and materialsData presented in the review are available in the references listed below.

Authors’ contributionsSilvia Magni-Manzoni conducted the literature review, drafted and reviewedthe manuscript.

Competing InterestsThe author has no competing interests.

Consent for publicationWritten informed consent was obtained from the patients' guardians/parentsfor the publication of images in the present review.

Magni-Manzoni Pediatric Rheumatology (2016) 14:33 Page 8 of 10

Received: 14 March 2016 Accepted: 19 May 2016

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