Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.
Juvenile idiopathic arthritis
Paediatrics and child health · UK scope · Sources checked 27 Aug 2026 · Clinical review pending
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Hot joint or systemically unwell child
Fever with one very painful immobile joint, sepsis physiology, severe night pain, cytopenia, unexplained bruising or bone tenderness requires urgent infection and malignancy assessment before a JIA diagnosis.
Action: Use ABCDE if unwell, obtain urgent paediatric and orthopaedic assessment, cultures and imaging as indicated and start septic-arthritis treatment promptly without injecting corticosteroid into an unexcluded infected joint.
Overview
Recognise persistent inflammatory arthritis in children, exclude infection and malignancy, classify subtype and institute early rheumatology, uveitis surveillance, rehabilitation and treat-to-target medicine before irreversible joint damage.
Ask onset, number and pattern of joints, morning function, limp, fatigue, fever, rash, eye symptoms, bowel disease, psoriasis, infection and family history. Observe play, floor rise and gait before examining every joint, enthesis, spine, skin, nails, eyes, nodes, liver and spleen. Compare passive range and muscle bulk rather than relying on visible swelling alone.
JIA is a clinical diagnosis of exclusion after six weeks of arthritis, but referral should occur as soon as inflammatory arthritis is suspected. Oligoarticular disease affects one to four joints in the first six months and carries important silent uveitis risk. Polyarticular disease affects five or more. Enthesitis-related arthritis often affects older boys, lower limbs, entheses or sacroiliac joints.
Fever pattern, evanescent rash and organ inflammation suggest systemic JIA, a cytokine-driven disease in which arthritis may appear after systemic symptoms. Persistently high fever with cytopenia, liver dysfunction, rising ferritin and falling fibrinogen suggests macrophage activation and belongs to the separate emergency pathway.
Aetiology
01
Polygenic immune susceptibility
Multiple HLA and immune-regulatory variants interact with developmental and environmental factors, but no single trigger explains most JIA.
02
Loss of synovial tolerance
Adaptive and innate immune activation persists within synovium, producing chronic arthritis after infection and trauma have resolved or been excluded.
03
Subtype-specific pathways
Autoantibody-associated oligoarthritis, enthesitis-related disease and systemic cytokine-driven arthritis have overlapping joints but distinct biology and risks.
04
Environmental immune interaction
Infection, microbiome and other exposures may modify risk, although routine searches for one causal infection are not clinically useful.
Pathophysiology
1
Synovial inflammation
Activated immune cells and cytokines thicken synovium, increase fluid and produce warmth, restriction and prolonged morning stiffness.
2
Pannus and structural damage
Uncontrolled synovitis erodes cartilage and bone, while pain and guarding create muscle wasting, contracture and altered growth.
3
Growth plate effects
Local hyperaemia can lengthen one limb early, while chronic inflammation and glucocorticoids later impair overall growth and bone acquisition.
4
Silent ocular inflammation
Anterior uveal immune inflammation can remain asymptomatic while creating synechiae, cataract, glaucoma and permanent visual loss.
Clinical features and red flags
Inflammatory joint pattern
Morning stiffness, swelling, warmth and restricted passive movement improve with activity and may present as limp or limb avoidance.
Oligoarticular pattern
One to four joints, often knees or ankles in a younger ANA-positive child, carries substantial silent uveitis risk.
Polyarticular pattern
Five or more small and large joints with symmetrical limitation may be RF negative or an adolescent RF-positive rheumatoid phenotype.
Enthesitis-related pattern
Lower-limb arthritis, heel or tendon-insertion pain, hip or sacroiliac symptoms and acute uveitis suggest spondyloarthritis spectrum.
Psoriatic pattern
Arthritis with psoriasis, dactylitis, nail pitting or a close family history supports juvenile psoriatic disease.
Red flags requiring action
Acutely painful hot swollen joint with fever or refusal to move is septic arthritis until urgently assessed.
Night pain, bone tenderness, weight loss, bruising, pallor, lymphadenopathy, hepatosplenomegaly or cytopenia raises leukaemia or other malignancy.
Red painful photophobic eye or reduced vision requires same-day ophthalmology, but JIA uveitis is often asymptomatic and must be screened before symptoms.
Persistent quotidian fever, evanescent rash, serositis or organ enlargement suggests systemic JIA and creates macrophage-activation risk.
Investigations
01First-line FBC film ESR and CRPFirst stepFirst line
Why
Assess inflammation, anaemia, cytopenia and malignant or infectious warning features.
Interpretation and limitations
Normal inflammatory markers do not exclude limited JIA; cytopenia or blasts redirects urgently toward malignancy or macrophage activation.
02ANA RF anti-CCP and HLA-B27 selectively
Why
Stratify uveitis risk and refine polyarticular or enthesitis-related phenotype rather than diagnose arthritis alone.
Interpretation and limitations
Positive ANA is common and nonspecific; interpret every antibody within examination and subtype context.
03Ultrasound with Doppler
Why
Confirm effusion, synovial hypertrophy and hyperaemia in an accessible uncertain joint and guide injection.
Interpretation and limitations
Imaging supports clinical synovitis but cannot safely distinguish infection without aspiration when the acute phenotype is concerning.
04MRI of deep or axial joints
Why
Assess hip, temporomandibular, sacroiliac, marrow or early structural disease not fully seen clinically.
Interpretation and limitations
Use contrast and sedation only when the clinical question warrants them; marrow abnormality may reveal an alternative diagnosis.
Differential diagnosis
01
Septic arthritis or osteomyelitis
Acute severe pain, fever, immobility and raised inflammatory markers requires urgent culture, imaging and source control.
02
Malignancy
Night pain, bony rather than joint tenderness, cytopenia, bruising, systemic symptoms or organ enlargement suggests leukaemia or bone tumour.
03
Reactive or postinfectious arthritis
Arthritis after gastrointestinal, genitourinary or viral infection may resolve within weeks but needs follow-up if persistence meets JIA duration.
04
Hypermobility or mechanical pain
Activity-related pain without morning stiffness, objective swelling, warmth or restricted passive movement supports a mechanical or non-inflammatory cause.
05
Connective tissue or vasculitic disease
Rash, nephritis, cytopenia, complement consumption, proximal muscle weakness or multisystem inflammation suggests lupus, juvenile dermatomyositis or systemic vasculitis.
Management
01Exclude emergencyProtect hot joints and marrowFirst stepArthritis accompanies fever, severe pain, systemic illness or malignancy clues.+
1Arrange urgent paediatric and orthopaedic assessment with FBC film, cultures and imaging.
2Aspirate and treat possible septic arthritis before any intra-articular corticosteroid.
3EscalationEscalate cytopenia, night pain, bruising or organ enlargement through malignancy pathways.
02ReferConfirm persistent inflammatory arthritisSwelling or restricted movement and morning stiffness suggests JIA.+
1Refer promptly to paediatric rheumatology without waiting six weeks before initiating the referral.
2Map every joint, enthesis, eye and systemic feature and obtain focused baseline tests.
3
Complications
01
Joint damage and contracture
Persistent synovitis erodes cartilage and bone and restricts range, leading to deformity, pain and long-term functional loss.
02
Chronic anterior uveitis
Silent eye inflammation can cause cataract, glaucoma, band keratopathy and irreversible visual impairment without scheduled slit-lamp screening.
03
Growth and bone effects
Persistent inflammation, reduced activity, poor nutrition and glucocorticoid exposure can impair height, puberty, muscle development and peak bone mass.
04
Medicine toxicity and infection
Methotrexate and biologics cause cytopenia, liver abnormalities and infection risk that require screening, vaccination and laboratory ownership.
05
Educational and psychological burden
Pain, fatigue, frequent appointments and visible physical difference affect school, sleep, mood, friendships and transition towards independent self-management.
Monitoring and follow-up
Count active and restricted joints and record morning function, pain, school and validated functional outcome at each review.
Measure height, weight, puberty, muscle bulk, limb length and bone or fracture risk during sustained disease.
Complete slit-lamp examinations at the risk-based interval and track any uveitis separately from joint activity.
During methotrexate monitor FBC, liver and renal function and confirm once-weekly dosing at every contact.
Before and during biologics screen infection and tuberculosis according to agent, update non-live vaccines and review live-vaccine restrictions.
Assess physiotherapy, orthoses, physical activity, sleep, fatigue, mood and school participation.
Begin adherence, contraception, self-injection and adult-service transition skills early in adolescence.
Special situations
Young children show stiffness
A toddler may stop walking after waking or resist dressing rather than describe joint pain or morning stiffness.
ANA predicts eyes not diagnosis
Antinuclear antibody helps set uveitis surveillance intensity but is neither required nor sufficient to diagnose JIA.
Quiet joints can hide uveitis
Ocular inflammation can progress while arthritis is inactive, so screening cannot be cancelled because movement improves.
Six weeks defines not delays
The duration criterion supports classification but should never postpone specialist referral for convincing inflammatory arthritis.
Treat function and inflammation
Normal inflammatory markers or little pain cannot justify accepting persistent synovitis, contracture or school restriction.
Common pitfalls
01
Waiting six weeks before referring suspected JIA.
02
Injecting a joint before excluding infection.
03
Using ANA as a diagnostic yes-or-no test.
04
Stopping eye screening when arthritis improves.
05
Repeating systemic steroids instead of escalating disease modification.
06
Overlooking malignancy in night pain and cytopenia.
07
Allowing weekly methotrexate to be prescribed as daily.
Practice
Two practice questions
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Question 1 of 2
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Paediatrics and child healthOriginal SBA
Silent eye protection
A young ANA-positive child with oligoarticular JIA has no eye pain, redness or visual complaint. What is the most important eye-management step?
Sources and review status4 sources · checked 27 Aug 2026 · clinical review pending+
Sources
Sources and review status
National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 27 Aug 2026; clinical approval remains outstanding.
Investigations exclude mimics and establish baseline. FBC and film assess cytopenia and malignancy, ESR or CRP inflammation, renal and liver function systemic or treatment effects. ANA is not a diagnostic screening test and may be positive in healthy children. Ultrasound confirms synovitis; MRI defines hip, temporomandibular, sacroiliac or marrow disease.
Treatment aims inactive disease and normal participation. NSAIDs provide temporary symptom relief. Intra-articular triamcinolone treats selected active joints, ideally with child-centred analgesia or sedation. Methotrexate is standard systemic disease-modifying therapy for persistent polyarthritis and some extended oligoarthritis, with folic acid and laboratory monitoring.
Biologic selection follows subtype and uveitis: TNF inhibitors, abatacept, tocilizumab and other agents are used through specialist pathways. Continue physiotherapy and protect range while avoiding prolonged immobilisation. Active arthritis generally benefits from appropriate physical activity; sport decisions are individual rather than blanket restriction.
Ophthalmology screening continues even when joints are controlled because ocular and articular courses differ. Children need rapid eye review for pain, redness, photophobia or reduced vision in addition to scheduled slit-lamp visits. Transition planning develops self-management, medicine knowledge and reproductive counselling before adult transfer.
Key points
JIA is arthritis beginning before age 16, persisting for at least six weeks and remaining unexplained after infection, malignancy and other inflammatory disease are excluded.
Inflammatory clues are joint swelling, warmth, restricted movement, morning stiffness and improvement with activity; young children may limp or stop using a limb without reporting pain.
Classify oligoarticular, polyarticular RF-positive or negative, systemic, enthesitis-related, psoriatic and undifferentiated disease because risks and treatment differ.
No blood test diagnoses JIA: ESR and CRP measure inflammation, ANA estimates uveitis risk, RF and anti-CCP refine phenotype and HLA-B27 supports selected enthesitis-related presentations.
Use ultrasound to detect effusion and synovitis and MRI for deep joints, sacroiliac disease, marrow or structural questions; aspirate urgently when infection is possible.
Refer suspected persistent inflammatory arthritis promptly to paediatric rheumatology and begin physiotherapy, occupational therapy and school support rather than waiting six weeks to make a referral.
Oligoarticular disease often responds to intra-articular corticosteroid, while persistent polyarthritis generally requires early weekly methotrexate and treat-to-target monitoring.
Back pain, enthesitis, hip arthritis, inflammatory bowel symptoms or acute anterior uveitis suggests enthesitis-related arthritis and spondyloarthritis spectrum.
Growth faltering, leg-length difference, contracture or delayed puberty indicates sustained inflammation or treatment toxicity requiring accelerated control.
05Synovial aspiration
Why
Obtain cell count, Gram stain and culture when septic arthritis or crystal disease is plausible.
Interpretation and limitations
Aspiration and urgent orthopaedic management precede corticosteroid injection when infection has not been excluded.
06Scheduled slit-lamp examination
Why
Detect asymptomatic anterior uveitis before cataract, glaucoma and visual damage develop.
Interpretation and limitations
Screening interval depends on age, ANA, subtype and duration and continues despite absent eye symptoms.
Start activity, pain, physiotherapy and school support while classification is completed.
03Treat targetAchieve inactive diseaseSpecialist assessment confirms JIA and defines subtype and severity.+
1Use intra-articular steroid for selected oligoarthritis and early methotrexate for persistent systemic joint burden.
2EscalationEscalate to a subtype-appropriate biologic when treat-to-target milestones are not met.
3Minimise systemic glucocorticoid exposure and measure function as well as joint count.
04Protect eyesScreen silent uveitisJIA is diagnosed regardless of reported visual symptoms.+
1Arrange slit-lamp surveillance at the age, ANA, subtype and duration-specific interval.
2Treat detected uveitis jointly with ophthalmology and rheumatology and monitor medicine toxicity.
3Provide same-day eye review for pain, redness, photophobia or reduced vision between screens.
Key medicines and prescribing safety3 treatments · regimens, roles and cautions+
Reduces pain and stiffness but does not reliably prevent structural damage as sole treatment for persistent active JIA.
Naproxen
For inflammatory arthritis in children over 5 years, a common specialist regimen is 10 mg/kg/day orally in two divided doses with food, maximum 1 g/day, used as a short symptom bridge while disease-modifying control is established.
Review renal disease, dehydration, asthma sensitivity, gastrointestinal bleeding and other NSAIDs; use the lowest effective duration and do not allow symptom improvement to delay disease-modifying escalation.
Produces prolonged local control in active oligoarticular joints while limiting systemic glucocorticoid exposure.
Intra-articular triamcinolone hexacetonide
A common paediatric large-joint regimen is up to 1 mg/kg, maximum 40 mg in one joint, with lower joint-specific doses and a total-session plan determined by the rheumatology injection service.
Exclude infection first, use analgesia or sedation and sterile technique, counsel about transient flare, skin atrophy and hypopigmentation and pair injection with rehabilitation.
First-line conventional disease-modifying treatment for persistent polyarticular and extended oligoarticular JIA and associated uveitis pathways.
Methotrexate
Use 10–15 mg/m² once weekly, commonly to a maximum 25 mg weekly, by oral or subcutaneous route with folic-acid supplementation on a separate schedule; specialist titration follows response and laboratory monitoring.
Weekly dosing errors can be fatal; monitor FBC, liver and renal function, review infection and vaccination, avoid pregnancy and address nausea, mouth ulcers, lung symptoms and interacting medicines.
Escalate inadequate disease control to a biologic matched to subtype, uveitis and prior treatment; do not allow repeated steroid courses to substitute for disease-modifying therapy.
Schedule slit-lamp screening from diagnosis according to age, ANA, subtype and disease duration because uveitis is commonly painless and externally invisible.
Immunisation, infection screening, contraception when age-relevant, growth, bone, mental health and transition belong in every long-term treatment plan.