High-yield overview
Chronic Childhood Inflammatory Arthritis
Under 16 yearsOnset
greater than 6 weeksDuration
7 subtypes (ILAR)Types
Most common jointKnee
ILAR Classification
Oligoarticular
Pattern≤4 joints. Most common.
TreatmentNSAIDs, intra-articular steroids
Polyarticular RF-
Pattern≥5 joints, RF negative.
TreatmentDMARDs, biologics
Polyarticular RF+
Pattern≥5 joints, RF positive.
TreatmentDMARDs, biologics
Systemic
PatternFever, rash, arthritis.
TreatmentBiologics (IL-1, IL-6)
Critical Must-Knows
- Oligoarticular: Most common type. 4 or fewer joints.
- Polyarticular: 5 or more joints. More severe.
- Systemic (Still's): Fever, rash, serositis.
- Growth Disturbance: Initial overgrowth, then undergrowth.
- Biologics: Revolutionized medical treatment.
Clinical Pearls
- "Oligoarticular most common
- "Knee overgrowth then undergrowth
- "Biologics are first-line
- "Surgery after medical optimization
Growth Disturbance
JIA causes characteristic growth disturbance in the affected limb.
- Initial: Inflammation → hyperemia → physeal overgrowth (limb lengthening).
- Later: Physeal damage → premature closure → undergrowth (limb shortening).
- Net Effect: Often leg length discrepancy.
- Knee most affected: Valgus deformity common.
JIA Subtypes
| Type | Joints | Features |
|---|---|---|
| ≤4 | Most common, uveitis risk | |
| ≥5 | Symmetric, moderate | |
| ≥5 | Similar to adult RA | |
| Variable | Fever, rash, serositis |
At a Glance Table
| Aspect | Details |
|---|---|
| Definition | Chronic arthritis in children under 16, lasting over 6 weeks |
| Most Common Subtype | Oligoarticular (4 or fewer joints) |
| Key Feature | Joint inflammation with growth disturbance |
| Growth Pattern | Initial overgrowth (hyperemia) then undergrowth (physeal damage) |
| Treatment Revolution | Biologics (TNF inhibitors, IL-1/IL-6 blockers) |
| Surgery | Reserved for refractory contractures or end-stage joints |
Mnemonic
JIA TJIA Types
| O | Oligoarticular ≤4 joints, most common |
| P | Polyarticular ≥5 joints |
| S | Systemic Fever, rash |
| E | Enthesitis-Related HLA-B27 associated |
| P | Psoriatic Psoriasis |
| O | Oligoarticular ≤4 joints, most common | E | Enthesitis-Related HLA-B27 associated |
| P | Polyarticular ≥5 joints | P | Psoriatic Psoriasis |
| S | Systemic Fever, rash |
Hook:OPSEP - Oligo, Poly, Systemic, Enthesitis, Psoriatic.
Mnemonic
OUGrowth Changes
| O | Overgrowth Early hyperemia |
| U | Undergrowth Late physeal damage |
| O | Overgrowth Early hyperemia |
| U | Undergrowth Late physeal damage |
Hook:OU - Overgrowth first, Undergrowth later.
Mnemonic
OAFYUveitis Risk Factors
| O | Oligoarticular Highest risk subtype |
| A | ANA Positive Antinuclear antibody |
| F | Female Girls more affected |
| Y | Young Onset Earlier onset higher risk |
| O | Oligoarticular Highest risk subtype | F | Female Girls more affected |
| A | ANA Positive Antinuclear antibody | Y | Young Onset Earlier onset higher risk |
Hook:OAFY - Oligo, ANA+, Female, Young.
Overview/Epidemiology
Juvenile Idiopathic Arthritis (JIA) is chronic inflammatory arthritis in children.
- Definition: Arthritis in children under 16, lasting greater than 6 weeks, with no other cause.
- Incidence: 1-4 per 10,000 children.
- Classification: ILAR classification (7 subtypes).
Pathophysiology and Mechanism
Pathophysiology of Joint Damage
- Chronic synovitis leads to pannus formation.
- Pannus erodes cartilage and subchondral bone.
- Joint destruction progresses if inflammation uncontrolled.
Growth Disturbance Mechanism
- Early Phase: Chronic inflammation causes hyperemia around physis.
- Hyperemia increases blood flow → physeal overgrowth → limb lengthening.
- Late Phase: Prolonged inflammation damages physeal chondrocytes.
- Physeal damage → premature closure → limb shortening.
- Net Effect: Often initial lengthening followed by shortening.
Common Joint Involvement
- Knee: Most commonly affected. Valgus deformity, flexion contracture.
- Hip: Flexion-adduction contracture, coxa valga.
- Cervical Spine: C1-C2 instability in severe polyarticular JIA.
Classification Systems
ILAR Classification (International League of Associations for Rheumatology)
- Oligoarticular: ≤4 joints in first 6 months. Most common (50%). Uveitis risk.
- Polyarticular RF-negative: ≥5 joints, RF negative. Moderate severity.
- Polyarticular RF-positive: ≥5 joints, RF positive. Similar to adult RA. Worst prognosis.
- Systemic (Still's Disease): Quotidian fever, salmon-pink rash, hepatosplenomegaly. IL-1/IL-6 driven.
- Enthesitis-Related Arthritis: HLA-B27 associated. Axial involvement. Related to ankylosing spondylitis.
- Psoriatic Arthritis: Arthritis with psoriasis or dactylitis.
- Undifferentiated: Does not fit other categories.
Clinical Assessment
History:
- Joint pain, swelling, stiffness.
- Morning stiffness (improves with activity).
- Systemic symptoms (fever, rash in systemic JIA).
- Eye symptoms (uveitis - especially oligoarticular).
Physical Exam:
- Joints: Swelling, warmth, effusion, ROM limitation.
- Gait: Antalgic.
- Leg Length: Discrepancy.
- Contractures: Hip, knee flexion.
- Eyes: Refer for slit lamp (uveitis).
Investigations
Blood:
- ESR, CRP: Elevated.
- ANA: Positive in oligoarticular (uveitis risk).
- RF: Positive in RF+ polyarticular.
- HLA-B27: Enthesitis-related.
Imaging:
- X-ray: Soft tissue swelling, osteopenia, erosions (late).
- MRI: Synovitis, effusion.
Management Algorithm
Medical Management
- NSAIDs: First-line for mild disease.
- Intra-articular Steroids: For oligoarticular.
- DMARDs: Methotrexate for polyarticular.
- Biologics: TNF inhibitors (etanercept, adalimumab), IL-1/IL-6 inhibitors for systemic JIA.
- Goal: Remission, prevent joint damage.
Algorithm
Surgical Techniques
Soft Tissue Releases
Indications: Fixed contractures not responding to physio/splinting.
Knee:
- Posterior capsular release.
- Hamstring lengthening.
- Post-op: Aggressive physio, night splinting.
Hip:
- Iliopsoas, rectus, adductor release.
- May need open release for severe contracture.
Complications
| Complication | Context | Management |
|---|---|---|
| Uveitis | Oligoarticular, ANA+ | Regular slit lamp screening |
| Growth Disturbance | Chronic inflammation | Control disease, address LLD |
| Joint Destruction | Uncontrolled synovitis | Early biologic therapy |
| Flexion Contractures | Chronic inflammation | Physio, splinting, release |
| Cervical Instability | Severe polyarticular | Cervical spine precautions |
Postoperative Care
- Aggressive Physiotherapy: Essential to maintain gains.
- Splinting: Night splints to prevent recurrence.
- Continue Medical Therapy: Do not stop biologics/DMARDs.
- Rheumatology Co-management: Essential.
- Monitor for Recurrence: Contractures can recur.
Outcomes/Prognosis
- Biologics Era: Dramatically improved outcomes.
- Oligoarticular: Best prognosis.
- RF+ Polyarticular: Worse prognosis, similar to adult RA.
- Systemic: Variable, can be severe.
Controversies and Areas of Uncertainty
- Classification in flux: A PRINTO consensus is moving toward a biology-based system (e.g. systemic JIA, RF-positive arthritis, enthesitis/spondylitis-related, early-onset ANA-positive arthritis) that may eventually replace the descriptive ILAR categories. Exam answers should acknowledge ILAR as current standard while noting the proposed revision.
- Systemic JIA as an autoinflammatory disease: Increasingly viewed as IL-1/IL-6-driven autoinflammation rather than classic autoimmune arthritis, supporting first-line IL-1/IL-6 blockade and a possible "window of opportunity" for early biologics.
- When to start biologics: Debate between early aggressive biologic use to prevent damage versus a step-up strategy after methotrexate failure, balancing cost, access and long-term safety.
- Treatment de-escalation: Optimal timing and method of tapering biologics after sustained remission remain unresolved; flare risk on withdrawal is significant.
- Surgical timing and choice: Diminishing role of synovectomy and arthroplasty in the biologic era; uncertainty over epiphysiodesis timing for inflammation-driven leg-length discrepancy that may partially self-correct once disease is controlled.
- Macrophage activation syndrome (MAS): A life-threatening complication of systemic JIA; thresholds for diagnosis and the role of anakinra in treatment continue to evolve.
Evidence Base
Level I
Lovell et al. — Etanercept in polyarticular JRA (RCT)
Key Findings:
- Landmark double-blind RCT: 69 children with methotrexate-refractory polyarticular JIA
- 74% responded in open-label phase; on withdrawal, disease flare in 28% (etanercept) vs 81% (placebo)
- Median time to flare over 116 days vs 28 days with placebo (less than 0.001)
Clinical Implication: First RCT proving a TNF inhibitor controls refractory JIA — opened the biologic era.
Source: N Engl J Med 2000;342:763-9
Guideline
Petty et al. — ILAR classification, 2nd revision (Edmonton 2001)
Key Findings:
- Defines the seven mutually exclusive ILAR categories used worldwide
- Arthritis onset under 16 years, persisting over 6 weeks, no other cause
- Categories: oligo (persistent/extended), poly RF-neg, poly RF-pos, systemic, ERA, psoriatic, undifferentiated
Clinical Implication: The universal classification framework for JIA subtyping and trials.
Source: J Rheumatol 2004;31:390-2
Level V
Ravelli & Martini — Juvenile idiopathic arthritis (review)
Key Findings:
- Authoritative review of heterogeneous JIA arthritides of unknown cause
- Prognosis greatly improved by anticytokine agents for conventional-therapy-resistant disease
- Subtype-specific presentation, genetics and outcome
Clinical Implication: Subtype drives prognosis and treatment selection.
Source: Lancet 2007;369:767-78
Level II
Malattia et al. — Tocilizumab radiographic progression (TENDER & CHERISH)
Key Findings:
- Post hoc radiographic analysis of two RCTs (systemic and polyarticular-course JIA)
- Wrist/hand films scored by adapted Sharp-van der Heijde and Poznanski methods over 104 weeks
- Most patients showed no structural progression on IL-6 blockade
Clinical Implication: IL-6 blockade may halt structural joint damage, not just symptoms.
Source: Arthritis Res Ther 2020;22:211
Level III
Wallace et al. — Validation of clinical remission criteria (OMERACT)
Key Findings:
- Validated criteria for inactive disease, clinical remission on and off medication
- Built from 34-country Delphi survey and chart review of 437 JIA patients
- Patients reaching off-medication remission stayed disease-free longest
Clinical Implication: Provides the treat-to-target endpoints (inactive disease, remission) for JIA.
Source: J Rheumatol 2006;33:789-95
Level IV
Martin et al. — Adolescent total knee arthroplasty
Key Findings:
- 29 TKAs in 19 patients aged 20 years or younger (JIA the leading diagnosis)
- Implant survivorship 96% at 5 years and 94-95% at 10 years
- TKA volume for inflammatory arthritis has fallen with biologic therapy
Clinical Implication: End-stage TKA is durable but increasingly rare; reserve for quiescent, destroyed joints.
Source: Arthroplast Today 2017;3:105-9
Guideline
Beukelman et al. — ACR treatment recommendations for JIA
Key Findings:
- ACR recommendations on initiation and safety monitoring of JIA therapeutics
- Treatment by disease group and prognostic features rather than ILAR category alone
- Escalation to DMARDs/biologics for poor-prognosis or refractory disease
Clinical Implication: Anchors stepwise medical escalation in JIA.
Source: Arthritis Care Res 2011;63:465-82
Guideline
Cassidy & Petty — Textbook of Pediatric Rheumatology
Key Findings:
- Standard reference for ILAR classification detail
- Orthopaedic manifestations and growth disturbance
- Multidisciplinary management principles
Clinical Implication: Core reference for paediatric inflammatory arthritis.
Source: Elsevier (current edition)
Viva Scenarios
Use these scenarios to practise clinical reasoning and management decisions
CLINICAL SCENARIOStandard
Leg Length Discrepancy in JIA
CLINICAL PROMPT
"10-year-old with oligoarticular JIA affecting the left knee. 3cm left leg lengthening noted."
PRACTICAL APPROACH
This is characteristic **growth disturbance in JIA**. The chronic inflammation causes **hyperemia and physeal overgrowth** initially, leading to leg lengthening. If it continues, the physis may be damaged and undergo premature closure, causing eventual shortening. Management: Ensure **medical management is optimized** (DMARDs/biologics) to control inflammation. For the leg length discrepancy, use a **shoe raise** for now. If significant and ongoing, consider **epiphysiodesis** of the longer leg at appropriate timing.
KEY CLINICAL POINTS
Overgrowth from hyperemia
Optimize medical treatment
Shoe raise or epiphysiodesis
COMMON PITFALLS
Not addressing inflammation
FURTHER QUESTIONS
"What is the most common JIA subtype?"
CLINICAL SCENARIOStandard
Knee Flexion Contracture
CLINICAL PROMPT
"Same patient has a 30-degree knee flexion contracture despite physiotherapy."
PRACTICAL APPROACH
A persistent knee flexion contracture despite conservative measures may need **soft tissue release**. First, ensure **medical treatment is optimized** (no active synovitis). Physiotherapy and serial casting/splinting should be tried. If still contracted, **posterior capsular release** with hamstring lengthening may be needed. Post-op, aggressive physiotherapy is essential.
KEY CLINICAL POINTS
Optimize medical treatment first
Physio, splinting, serial casting
Posterior release if refractory
COMMON PITFALLS
Operating on active synovitis
FURTHER QUESTIONS
"What complications can occur in JIA eyes?"
CLINICAL SCENARIOStandard
Cervical Spine in JIA
CLINICAL PROMPT
"Teenager with long-standing polyarticular JIA needs tonsillectomy. What are the anaesthetic concerns?"
PRACTICAL APPROACH
Patients with **polyarticular JIA** can have **cervical spine involvement** with C1-C2 instability. Before any surgery requiring intubation, I would obtain **flexion-extension lateral cervical spine X-rays** to assess for atlantoaxial instability. If unstable, **awake fibreoptic intubation** or **manual inline stabilization** during intubation is required. I would also ensure **TMJ function** is adequate as some JIA patients have limited mouth opening. I would communicate with the anaesthetist and document the cervical spine status.
KEY CLINICAL POINTS
C1-C2 instability possible
Pre-op cervical spine imaging
Communicate with anaesthetist
TMJ involvement may limit access
COMMON PITFALLS
Not assessing cervical spine
Not communicating concerns
FURTHER QUESTIONS
"What other conditions cause C1-C2 instability?"
MCQ Practice Points
Type MCQ
Q: What is the most common JIA subtype? A: Oligoarticular (≤4 joints).
Growth MCQ
Q: What causes initial leg lengthening in JIA? A: Hyperemia from inflammation causes physeal overgrowth.
Eye MCQ
Q: What eye complication is associated with oligoarticular JIA? A: Uveitis (especially if ANA positive).
RF+ MCQ
Q: Which JIA subtype has the worst prognosis? A: RF-positive polyarticular - similar to adult rheumatoid arthritis.
Systemic JIA MCQ
Q: What is the characteristic rash in systemic JIA? A: Salmon-pink, evanescent rash that appears with fever spikes.
Cervical Spine MCQ
Q: What cervical spine concern exists in polyarticular JIA? A: C1-C2 instability - requires pre-operative assessment before intubation.
Guidelines, Registries & Global Practice
Global epidemiology
- JIA is the most common chronic inflammatory rheumatic disease of childhood. Population-based studies show wide variation: incidence roughly 1.6-23 per 100,000/year and prevalence 3.8-400 per 100,000.
- Oligoarticular onset predominates in European/North American cohorts; systemic and polyarticular onset are relatively more common in parts of Asia, Africa and Latin America.
- Female predominance overall (especially ANA-positive oligoarticular and uveitis); enthesitis-related arthritis is more common in older boys.
Major guidelines — side by side
| Body | Scope | Core position |
|---|---|---|
| ACR (US) | Treatment by disease group + prognostic features | Stepwise escalation: NSAIDs/intra-articular steroid → methotrexate → biologic for poor-prognosis or refractory disease |
| EULAR/PReS (Europe) | Points to consider, systemic JIA & non-systemic | Treat-to-target to inactive disease; early biologic in systemic JIA; window-of-opportunity concept |
| BSPAR / NICE (UK) | Biologic eligibility & uveitis screening | Structured ophthalmology screening schedule; biologics for inadequate methotrexate response |
| ILAR (global) | Classification | Seven-category framework underpinning all guidelines |
Registry & long-term data
- Pharmacovigilance registries (e.g. German BiKeR, UK BSPAR-ETN/BCRD, US CARRA Registry, Pharmachild/PRINTO) track biologic safety — malignancy and serious-infection signals have been reassuring at population scale.
- Joint-replacement registries show end-stage arthroplasty for JIA is now uncommon; when performed, survivorship is good but technically demanding (small implants, deformity, osteopenia).
High- vs limited-resource practice variation
- Well-resourced settings: early methotrexate, prompt biologic access, protocolised slit-lamp uveitis screening, MDT (rheumatology, ophthalmology, physiotherapy, orthopaedics, psychology), structured adolescent transition to adult services.
- Limited-resource settings: delayed diagnosis, reliance on NSAIDs/steroids and methotrexate due to biologic cost/availability, higher burden of established deformity, contractures and growth disturbance at presentation — raising the relative role of orthopaedic soft-tissue and reconstructive surgery.
- Universal priorities: control inflammation early, screen the eyes, preserve growth and function, and assess the cervical spine and TMJ before any anaesthetic in polyarticular disease.
JUVENILE IDIOPATHIC ARTHRITIS
Clinical summary
TYPES
- •Oligoarticular (most common)
- •Polyarticular RF+/-
- •Systemic (Still's)
- •Enthesitis-related
GROWTH
- •Initial overgrowth (hyperemia)
- •Later undergrowth (physeal damage)
- •Leg length discrepancy
- •Valgus knee common
UVEITIS RISK
- •Oligoarticular subtype
- •ANA positive
- •Female
- •Young onset
TREATMENT
- •NSAIDs for mild
- •DMARDs (methotrexate)
- •Biologics (TNF, IL-1/6)
- •Physio essential
SURGERY
- •After medical optimization
- •Contracture release
- •Epiphysiodesis for LLD
- •Arthroplasty (rare)
CERVICAL SPINE
- •C1-C2 instability risk
- •Pre-op imaging
- •TMJ may limit mouth opening
- •Communicate with anaesthesia
Differential Diagnosis
| Condition | Distinguishing Features |
|---|---|
| Septic Arthritis | Acute, single joint, febrile, elevated WCC |
| Reactive Arthritis | Post-infectious, self-limiting |
| Lyme Arthritis | Endemic area, tick bite, Borrelia serology |
| Leukemia | Night pain, bone pain, abnormal blood film |
| Transient Synovitis | Hip, resolves within 2 weeks, normal bloods |