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Juvenile Idiopathic Arthritis



Group of inflammatory arthropathies affecting children <

16 years old


Best diagnostic clue

4 subtypes differ in clinical presentation and prognosis

Any affected joint has similar attributes

Large effusions

Osseous erosions

Cartilage destruction

Often bilateral but usually not symmetric

End-stage ankylosis

Carpus most frequent site of fusion

If cervical spine involved, fusion of bodies and posterior elements frequently occurs




Subsets differ in joints most likely to be affected

Oligoarticular (> 50% of cases)

Generally only 2-4 joints

Knee most frequent, followed by ankle and elbow

Psoriatic arthritis/enthesitis-related arthritis (10% of cases)

Sacroiliac joints, knee, ankle, hip

Polyarticular [RF(+) or RF(-)] (30% of cases)

5+ joints

Hands/feet; may involve all joints as in adult RA

Systemic (10% of cases)

Polyarticular, following pattern of adult RA

Location in hand/wrist different from adult RA

Pericapitate erosions predominate in carpus

Metacarpophalangeal involvement does not dominate interphalangeal involvement



Growth abnormalities common

Gracile long bones (narrow diameter, thin cortex)

Short stature, hypoplastic iliac wings

Due to chronic illness, lack of weight bearing

Early epiphyseal closure due to hyperemia

Hypoplastic cervical vertebral bodies

Due to body fusion prior to skeletal maturity

Morphology is normal, but fused bodies are uniformly small relative to unfused bodies

Micrognathia: Hypoplastic angle of mandible with temporomandibular joint erosions

Ballooned (enlarged) epiphyses

Overgrowth of epiphysis due to hyperemia from inflammatory synovitis

Results in prominent, enlarged epiphyses relative to diaphyses

Clinically, knobby enlarged joints

Especially prominent in knee, ankle, elbow

Enlarged notches

Due to pressure erosion from pannus

Noted in intercondylar notch of knee and trochlear notch in elbow


Radiographic Findings

Uniform osteopenia


Earliest radiographic signs

Periostitis: Seen only at earliest stages, in young child

Differential growth of epiphysis; often need contralateral side for comparison


Purely erosive disease


Uniform cartilage narrowing


Large effusions


Progressive destruction, with ankylosis at end-stage


Growth abnormalities

Short stature

Gracile long bones

Overgrown epiphyses with enlarged notches



MR Findings

MR provides information at early stage, prior to radiographic change

Effusions, tenosynovitis: High T2WI

Marrow edema: Low T1WI, high T2WI signal

Erosions: Low T1WI, high T2WI signal

Pannus: Thickened synovium

Low signal on T1WI

Low signal on T2WI, may be nodular, outlined by high signal effusion

Enhances with contrast administration

Menisci may appear small or compressed due to effusion

Contrast essential to distinguish active synovial inflammation from nonenhancing effusion or fibrotic pannus

May be used to evaluate for early physeal fusion when evaluating for growth potential



Cause unknown

Disordered immunoregulation reported

Possible latent viral infection (rubella suggested)

Likely not common cause among subsets



Associated with IL2RA (CD25) gene (IL-2 receptor α)

General susceptibility gene for autoimmune diseases; likely represents JIA susceptibility locus

JIA patients carrying TNF-α -308 GA/AA and -238 GA genotypes worse prognosis and lower response to anti-TNF-α drugs


Associated abnormalities

Oligoarticular: Serious risk of uveitis

May be complicated by blindness

Psoriatic arthritis/enthesitis-related arthritis

50% HLA-B27(+)

Polyarticular: Constitutional symptoms

Low-grade fever, weight loss


Rheumatoid factor positive in 20-30%

ANA(+) in 40%


Quotidian (daily spiking) fever, rash



Weight loss, myalgia

Neutrophilic leukocytosis, anemia

Rheumatoid factor and ANA (-); ESR



Hemophilic arthropathy

Toxic synovitis of hip

Chronic septic joint



 Lateral radiograph shows the unaffected knee in a child with oligoarticular juvenile idiopathic arthritis (JIA). This is shown for comparison.


 Lateral radiograph shows the contralateral affected knee in the same patient. Although at 1st glance this radiograph appears normal, there is significant overgrowth of the epiphyses of this knee. Note the femoral condyles, proximal tibial epiphysis, and in particular the patella . There is also crenulation or irregularity along the femoral condyles .



AP radiograph shows the normal knee in the same child.



AP radiograph of the affected knee was taken at the same distance and time. Note the enlargement of the femoral condylar and proximal tibial epiphyses. This occurs due to the hyperemia of the joint secondary to inflammation and synovitis. Such overgrowth, or ballooning, is often the 1st radiographic sign of JIA. Note also the more mature morphology of the medial tibial epiphysis . Without comparison radiographs, it may easily be missed.


PA radiograph shows the hand in a child with new onset of metacarpophalangeal pain and swelling (the right worse than the left). This left hand appears normal.


PA radiograph of the right hand in the same patient is shown. Compare the 3rd metacarpal head; it is enlarged and eroded. Additionally, there is relative overgrowth of the base of the proximal phalanx . Note the soft tissue swelling. This focally advanced skeletal maturation is secondary to hyperemia from the inflammatory process.



Lateral radiograph in a young child shows regular periosteal reaction extending along the phalanges . There is soft tissue swelling but no articular abnormality.




PA radiograph in the same child shows the same subtle but regular periosteal reaction . The differential diagnoses for this appearance include JIA, sickle cell dactylitis, and tuberculosis dactylitis. This proved to be an early manifestation of JIA.



Lateral radiograph of the cervical spine in JIA shows the typical ankylosis of posterior elements as well as vertebral bodies, extending from C2-C6 . With fusion at a young age, growth is arrested, leaving hypoplasia of the involved bodies compared with uninvolved ones .



Lateral radiograph in a JIA patient with C2-C6 fusion and hypoplasia over that interval is shown. There is micrognathia, with hypoplastic angles of the mandible and eroded temporomandibular joints .


AP radiograph of the knees in a patient with longstanding JIA shows ballooned overgrowth of the femoral condyles and widening of the intercondylar notch. Additionally, there is uniform cartilage thinning and prominent subchondral erosions.


AP radiograph in the same patient shows destruction of the hip joints with associated protrusio, typical of JIA.


PA radiograph of the carpus in a child with JIA shows early fusion at several sites, including capitatemetacarpal , trapezoidmetacarpal , trapeziumtrapezoid , and hamatetriquetrum . The cortex appears slightly irregular or crenulated. Carpal ankylosis is typical of JIA.


PA radiograph in a young adult who developed JIA as a teenager shows near-complete carpal ankylosis .This is common in JIA but is not expected in adult rheumatoid arthritis.



AP radiograph in a child with JIA shows erosions along the lateral femoral neck . This portion of the hip is within the capsule and constitutes a bare area of bone, which is not protected by cartilage. It is at risk for early erosion. There is also cartilage narrowing .


AP radiograph in the same child, 1 year later, shows the neck erosions have smoothed , leaving a thin neck at risk for fracture. There is complete cartilage loss as well as subchondral erosions .


AP radiograph shows JIA, with widening of the trochlear notch due to pressure erosion from pannus over a long period of time. The radial head is relatively enlarged  due to continual hyperemia in the joint. All growth centers may enlarge, but in the elbow, the radial head shows disproportionate overgrowth.


Coronal STIR MR of the sacroiliac joints in an 8 year old shows bilateral asymmetric sacroiliitis , with erosions and cysts . This is the enthesitis-related arthritis subtype of JIA.


AP radiograph shows classic severe JIA in a patient who is now an adult. There is overgrowth of the femoral condyles and a widened intercondylar notch superimposed on the erosive destructive inflammatory changes .


Lateral radiograph shows overgrowth of the femoral condyles and patella, developed secondary to chronic hyperemia prior to skeletal maturation. The widened intercondylar notch can be diagnosed on the lateral view by bowing of the Blumensaat line 


AP radiograph shows the adult sequela of JIA, with iliac wing hypoplasia and gracile femur which are the results of chronic illness and infrequent weight bearing. There is protrusio of the hip, with severe destruction .


PA radiograph shows ulnar tilt due to overgrowth of the radial styloid during the hyperemic growing stage of JIA. Note the matching overgrowth of the ulnar styloid . The collapsed radial aspect of the lunate likely resulted from erosions & impaction from mild trauma.



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