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Transient synovitis of the hip

Last updated 28 Mar 2026 · Inflammatory Arthritis

Introduction

Transient synovitis of the hip (also termed "irritable hip" or "pseudocoxalgia") is the most common cause of acute hip pain in children aged 3–10 years. It is a benign, self-limiting condition characterised by sterile inflammation of the hip joint capsule, typically following a viral upper respiratory tract infection. The condition affects 1 in 600 to 1 in 1000 children per year in Australia.

The primary clinical challenge is to distinguish transient synovitis from septic arthritis of the hip, as both present with acute hip pain and limp. Septic arthritis is a medical emergency requiring urgent joint aspiration and antibiotic therapy, whereas transient synovitis is managed conservatively with NSAIDs and rest. The Kocher criteria have been developed to assist with this differentiation.

Pathophysiology

Aetiology

Transient synovitis is thought to be post-viral in origin, occurring 1–4 weeks after an upper respiratory tract infection (commonly viral: rhinovirus, adenovirus, enterovirus). The viral infection triggers a sterile inflammatory response in the synovial membrane of the hip joint, with accumulation of inflammatory fluid in the joint space. The exact mechanism is not fully understood but likely involves immune-mediated inflammation rather than direct viral invasion of the joint.

Associated Conditions

  • Recent viral upper respiratory tract infection (history in 50–60% of cases)
  • Mild systemic viral illness symptoms (fever, cough, nasal congestion)
  • Exposure to other children with viral infections (high risk in childcare/school settings)

Natural History

Transient synovitis is self-limiting, with resolution typically occurring within 7–14 days in the majority of cases. Symptoms resolve gradually with conservative management (NSAIDs, rest, physiotherapy). Recurrence occurs in 2–10% of cases, typically within 1–2 years.

Clinical Presentation

History

Onset: Acute to subacute (over 24–72 hours). Pain: Localised to the hip, anterior thigh, or groin. Pain may be referred to the knee. Aggravating factors: Worse with weight-bearing and movement. Child often refuses to bear weight or limps. Associated symptoms: Low-grade fever in 20–30% of cases. Recent viral upper respiratory symptoms in 50–60% of cases.

Examination

Gait: Antalgic gait with refusal to bear weight on the affected limb. Child may crawl or require crutches. Hip examination: Hip flexion, abduction, and external rotation are preferred pain-reducing positions (frog-leg position). Internal rotation and adduction are painful and often restricted. General examination: Child appears comfortable at rest but guards the hip with movement. Systemic signs of infection (high fever, unwell appearance, significant lymphadenopathy) favour septic arthritis.

Investigations

  • Essential
    Kocher Criteria
    Four predictive features to distinguish transient synovitis from septic arthritis: (1) fever >39°C, (2) non-weight-bearing status, (3) CRP >20 mg/L, (4) ESR >40 mm/hr. Presence of all four criteria: 99% probability of septic arthritis. Zero criteria: <1% probability of septic arthritis.
  • Essential
    Inflammatory Markers (ESR, CRP)
    ESR and CRP help stratify risk. Both normal or mildly elevated (<20 mg/L CRP, <40 mm/hr ESR) favour transient synovitis. Both elevated favour septic arthritis.
  • Available
    Plain Hip X-ray
    May show joint effusion (widened joint space) but does not differentiate transient synovitis from septic arthritis. Useful to exclude other pathology (fracture, Perthes disease).
  • Available
    Ultrasound of Hip
    Sensitive for detecting joint effusion. Non-invasive and does not expose to radiation. Helpful if septic arthritis suspected; may show echogenic debris suggesting septic joint.

Severity Stratification

LOW RISK
Likely Transient Synovitis
Kocher criteria 0–1 factors present. Normal/mildly elevated inflammatory markers. Well-appearing child. No systemic signs of infection.
Primary care; conservative management; urgent specialist referral if criteria increase
MODERATE RISK
Diagnostic Uncertainty
Kocher criteria 2–3 factors present. Consider imaging and further investigation. Elevated inflammatory markers.
Primary care with specialist consultation; consider ultrasound or blood culture
HIGH RISK
Likely Septic Arthritis
All four Kocher criteria present (99% probability septic arthritis). High fever, unwell appearance, significantly elevated inflammatory markers.
Emergency department; urgent joint aspiration and antibiotic therapy

Directed Therapy

NSAIDs (First-Line)

💊
Ibuprofen
Nurofen® · NSAID
Paediatric Dose10 mg/kg per dose
RouteOral
FrequencyEvery 6–8 hours (max 4 doses/24 hrs)
Duration7–14 days
NotesSignificantly improves pain and mobility. Take with food. Assess response at 48 hours; if no improvement, review diagnosis.
PBS Status✓ PBS General Benefit
💊
Paracetamol
Panadol® · Non-opioid analgesic
Paediatric Dose15 mg/kg per dose
RouteOral
FrequencyEvery 4–6 hours (max 5 doses/24 hrs)
DurationAs needed
NotesLess effective than NSAIDs for transient synovitis. Use if NSAIDs contraindicated or as adjunct. Do not exceed 60 mg/kg/day.
PBS Status✓ PBS General Benefit

Activity Modification

Rest and immobilisation: Initially, avoid weight-bearing activities. Use crutches or wheelchair assistance for mobility. As pain improves (usually within 3–5 days), gradually increase weight-bearing and activities as tolerated.

Return to normal activities: Majority of children can return to school and normal play within 1–2 weeks. Sports and high-impact activities should be delayed until pain-free walking is achieved and inflammatory markers normalise.

Physiotherapy

Gentle hip mobility exercises once acute pain improves (days 3–5). Stretching of hip flexors and adductors (3–4 times daily, 30 seconds × 3 reps). Strengthening exercises (quadriceps, hip abductors, core) once pain resolves.

Acute Management

Initial Assessment and Risk Stratification

When a child presents with acute hip pain:

  • Detailed history: Onset (acute vs insidious), antecedent viral illness, fever, trauma, previous episodes of hip pain or limp.
  • Systematic examination: Vital signs (fever), general appearance (well vs unwell), hip range of motion (internal rotation most sensitive for restriction), Thomas test (hip flexion contracture).
  • Apply Kocher criteria: Assess presence/absence of: fever >39°C, non-weight-bearing, CRP >20, ESR >40.
  • Blood tests: ESR, CRP, blood culture if septic arthritis suspected (Kocher 2+ criteria).

Low-Risk Cases (0–1 Kocher Criteria)

Manage in primary care with NSAIDs and rest. Prescribe ibuprofen, provide analgesia advice, arrange follow-up at 48–72 hours. If symptoms improve significantly, continue conservative management. If symptoms persist or worsen, review diagnosis and consider imaging/specialist input.

Higher-Risk Cases (2–3+ Kocher Criteria)

Consider urgent imaging (ultrasound or MRI) to exclude septic arthritis. If imaging shows large joint effusion or debris, obtain blood culture and arrange urgent specialist assessment.

High-Risk Cases (All 4 Kocher Criteria)

This constellation carries 99% probability of septic arthritis. Urgent referral to hospital. Obtain blood cultures before antibiotic administration. Proceed with joint aspiration under ultrasound guidance. Initiate empiric intravenous antibiotics (e.g., ceftriaxone or cefotaxime) pending culture results.

Monitoring and Follow-Up

Short-Term Follow-Up (48–72 hours)

Review by phone or clinic visit within 48–72 hours of initial presentation. Check for improvement in pain, mobility, and ability to bear weight. If significant improvement (pain decreased by >50%, able to walk with minimal limp), continue conservative management. If minimal improvement or worsening, obtain imaging and consider specialist referral.

Resolution Timeline

Majority of children (>90%) achieve significant pain reduction within 3–5 days of starting NSAIDs. Complete resolution typically occurs within 1–2 weeks. Inflammatory markers usually normalise within 2–3 weeks. If symptoms persist beyond 3 weeks, review diagnosis and investigate for alternative pathology (Perthes disease, slipped capital femoral epiphysis, inflammatory arthropathy).

Special Populations

👶 Paediatrics (3–10 years)
Age-appropriate dosingUse weight-based dosing for ibuprofen and paracetamol. Ensure child-friendly formulations (liquid, chewable tablets).
ComplianceChildren may resist taking medications; involve parents in administration and provide clear written instructions.
👦 Adolescents (>10 years)
Adult-equivalent managementOlder adolescents usually tolerate adult-dose NSAIDs. Kocher criteria remain applicable; septic arthritis remains a possible differential diagnosis.
Aboriginal and Torres Strait Islander Health Considerations

Transient synovitis affects Aboriginal and Torres Strait Islander children at similar prevalence to other Australian populations. However, delayed diagnosis and management may occur due to geographic remoteness and limited access to healthcare services.

Diagnostic Delay
In remote communities, access to ESR, CRP, ultrasound, and specialist assessment may be delayed. Utilise Kocher criteria as a clinical tool requiring only history, examination, and simple blood tests. Initiate empiric conservative management while awaiting test results. Telehealth consultation with paediatrician for diagnostic support.
Limited Rehabilitation Services
Physiotherapy may not be available locally. Provide written home exercise programmes with clear diagrams. Train Aboriginal health workers to supervise simple stretching and strengthening exercises. Use video consultations for physiotherapy guidance.
Health System Gaps
Incomplete immunisation, higher rates of concurrent infections, and comorbid conditions may complicate presentation. Ensure up-to-date immunisation status. Screen for other acute or chronic infections. Provide holistic primary care addressing multiple health needs.
Follow-Up Adherence
Distance and transport challenges may affect follow-up attendance. Schedule follow-up reviews to coincide with other health appointments. Use SMS reminders. Consider home visits by community health workers.

Stewardship and Key Points

Key Messages

  • Kocher criteria are sensitive and specific: Use them to guide clinical decision-making regarding likelihood of septic arthritis versus transient synovitis.
  • NSAIDs are effective: Most children show marked improvement in pain and mobility within 48–72 hours of starting ibuprofen.
  • Conservative management is first-line: Avoid unnecessary imaging and investigations in low-risk cases (Kocher 0–1 criteria).
  • Septic arthritis is a medical emergency: High-risk cases (all four Kocher criteria) require urgent specialist assessment and joint aspiration.
  • Complete resolution is expected: More than 95% of children with transient synovitis recover fully within 2–3 weeks without long-term sequelae.

Red Flags Warranting Specialist Referral

Refer urgently if: High fever (>39°C) with inability to weight-bear and elevated inflammatory markers (CRP >20, ESR >40). Minimal improvement in pain/mobility after 5 days of NSAIDs. Presence of systemic features suggesting infection (unwell appearance, tachycardia, signs of sepsis).

References

  • 01
    Kocher MS, Zurakowski D, Kasser JR. Differentiating between septic arthritis and transient synovitis of the hip in children: an evidence-based clinical prediction algorithm. J Bone Joint Surg Am. 1999;81(12):1662-1670.
  • 02
    Caird MS, Flynn JM, Lebensburger JD, et al. Factors distinguishing septic arthritis from transient synovitis of the hip in children. J Bone Joint Surg Am. 2006;88(6):1251-1257.
  • 03
    Singhal R, Perry DC, Khan FN, et al. Diagnostic uncertainty in acute hip pain of childhood: transient synovitis or septic arthritis? Arch Dis Child. 2011;96(10):1164-1167.
  • 04
    Australian Paediatric Surveillance Unit (APSU). Surveillance of serious invasive infections in Australian children. 2023 Annual Report.