Transient Synovitis (Irritable Hip)
Transient synovitis is a self-limiting, benign inflammatory condition of the hip joint and is the most common cause of acute hip pain and limp in children aged 3-8 years. [1,2] While the condition resolves spontaneously within days to weeks, the critical clinical challenge is distinguishing it from septic arthritis, which requires emergency surgical drainage. [1,3]
Key Facts
| Fact | Detail |
|---|---|
| Definition | Self-limiting, non-infective inflammation of hip synovium |
| Incidence | 0.2% of children; most common cause of acute hip pain in children |
| Peak age | 3-8 years (range 9 months to 14 years) |
| Sex ratio | Male:Female = 2:1 |
| Laterality | Unilateral in 95%; bilateral in 5% |
| Duration | Usually resolves in 3-10 days |
| Aetiology | Post-viral inflammatory reaction (50% have recent URTI) |
| Key concern | Must exclude septic arthritis |
| Kocher criteria | 4 predictors: non-weight bearing, fever, ESR more than 40, WCC more than 12 |
| Prognosis | Excellent; complete resolution in virtually all cases |
Clinical Pearls
Pearl 1: Transient synovitis is a DIAGNOSIS OF EXCLUSION. You must always consider and rule out septic arthritis before making this diagnosis. When in doubt, aspirate the hip.
Pearl 2: The Kocher criteria were developed to distinguish transient synovitis from septic arthritis. With 0/4 criteria present, the probability of septic arthritis is only 0.2%. With 4/4 criteria, it is 99.6%.
Pearl 3: CRP is not part of the original Kocher criteria but was added by Caird et al. A CRP more than 20 mg/L significantly increases the probability of septic arthritis and should be included in the assessment.
Pearl 4: Always follow up children with transient synovitis. If symptoms persist beyond 2 weeks, consider Perthes disease and obtain a repeat hip X-ray or MRI.
Pearl 5: A well-appearing child with 0 Kocher criteria who is weight-bearing (even with a limp) can usually be managed as an outpatient with close follow-up.
Incidence and Prevalence
| Population | Rate |
|---|---|
| General paediatric population | 0.2% per year |
| Acute hip pain presentations (children) | 50-60% are transient synovitis |
| Recurrence rate | 4-17% will have second episode |
Demographics
| Factor | Association |
|---|---|
| Age | Peak 3-8 years; range 9 months to 14 years |
| Sex | Male predominance 2:1 |
| Laterality | Right = Left; Bilateral rare (5%) |
| Season | Year-round, slight increase with viral illness peaks |
Risk Factors
| Risk Factor | Notes |
|---|---|
| Recent viral illness | 50% have URTI in preceding 2 weeks |
| Age 3-8 years | Peak age range |
| Male sex | 2× more common in boys |
| Previous transient synovitis | Recurrence in 4-17% |
Seasonal Variation
| Season | Association |
|---|---|
| Autumn/Winter | Slight increase correlating with viral illness peaks |
| Otherwise | Year-round occurrence |
Stepwise Mechanism
Step 1: Preceding Viral Illness
- Up to 50% of children have recent upper respiratory tract infection
- Common viruses implicated: adenovirus, enterovirus, parvovirus B19, EBV
- Exact pathogen rarely identified
Step 2: Post-Infectious Inflammatory Response
- Immune-mediated reaction rather than direct infection
- Inflammatory cascade activates within hip synovium
- Cytokine release (IL-1, IL-6, TNF-α) triggers synovial inflammation
- No bacteria present in joint fluid (sterile)
Step 3: Synovial Inflammation
- Synovial membrane becomes hyperaemic and oedematous
- Increased synovial fluid production
- Joint capsule distends with effusion
- Histology: non-specific synovitis with lymphocyte infiltration
Step 4: Joint Effusion and Hip Irritability
- Effusion causes capsular distension
- Hip held in position of maximum capsular volume (flexion, abduction, external rotation)
- Pain and limited range of motion
- Protective muscle spasm
Step 5: Spontaneous Resolution
- Inflammatory response self-limits over 7-14 days
- Effusion gradually resorbs
- Full recovery of range of motion and function
- No permanent joint damage
Comparison with Septic Arthritis
| Feature | Transient Synovitis | Septic Arthritis |
|---|---|---|
| Aetiology | Post-viral, immune-mediated | Bacterial infection (Staph aureus) |
| Synovial fluid | Sterile, mildly inflammatory | Purulent, positive culture |
| WCC in fluid | Less than 50,000/mm³ | More than 50,000/mm³ |
| Systemic features | Minimal | Toxic, febrile, unwell |
| Joint damage | None | Rapid cartilage destruction |
| Treatment | Rest, NSAIDs | Emergency surgical drainage |
Typical History
| Feature | Description |
|---|---|
| Onset | Acute or subacute (over 24-48 hours) |
| Pain location | Hip, groin, thigh, or referred to knee |
| Limp | Antalgic gait; may refuse to weight bear |
| Activity | Usually still mobile; not systemically toxic |
| Fever | Usually absent or low-grade (less than 38°C) |
| Preceding illness | URTI in previous 1-2 weeks (50%) |
| Night pain | Usually absent (present in malignancy) |
Symptom Frequency
| Symptom | Frequency |
|---|---|
| Limp | 90-95% |
| Hip/groin pain | 80-90% |
| Referred knee pain | 20-40% |
| Reduced range of motion | 60-80% |
| Low-grade fever (less than 38°C) | 10-30% |
| Recent URTI | 50% |
| Refusal to weight bear | 30-40% |
Differential Diagnoses
| Condition | Key Distinguishing Features |
|---|---|
| Septic arthritis | Fever, toxic appearance, non-weight bearing, elevated inflammatory markers |
| Perthes disease | Persistent limp more than 2 weeks, insidious onset, age 4-10 years |
| Slipped capital femoral epiphysis (SCFE) | Older child/adolescent (10-16), obese, limited internal rotation |
| Juvenile idiopathic arthritis | Prolonged symptoms, multiple joints, morning stiffness |
| Osteomyelitis | Fever, bony tenderness, metaphyseal location |
| Fracture | History of trauma, point tenderness |
| Referred knee pain from hip pathology | Examine the hip in any child with knee pain |
| Malignancy (leukaemia, bone tumours) | Night pain, systemic symptoms, weight loss |
Red Flags
| Red Flag | Concern | Action |
|---|---|---|
| Temperature more than 38.5°C | Septic arthritis | Urgent aspiration |
| Non-weight bearing | Septic arthritis | Apply Kocher criteria |
| WCC more than 12,000 | Septic arthritis | Urgent aspiration |
| ESR more than 40 | Septic arthritis | Urgent aspiration |
| CRP more than 20 | Septic arthritis | Consider aspiration |
| Toxic/unwell appearance | Septic arthritis | Emergency assessment |
| Symptoms persisting more than 2 weeks | Perthes disease | Repeat imaging |
| Night pain | Malignancy | Further investigation |
Structured Examination
Observation
- General appearance: well vs toxic/unwell
- Gait: antalgic limp, Trendelenburg gait
- Posture: hip held in flexion, abduction, external rotation (position of comfort)
- Weight-bearing status
Palpation
- Check for groin tenderness (hip joint)
- Palpate thigh and knee (referred pain)
- No bony tenderness (differentiates from osteomyelitis/fracture)
Range of Motion (Affected Hip)
| Movement | Expected Finding |
|---|---|
| Flexion | May be limited by pain |
| Extension | Painful, limited |
| Internal rotation | Usually most restricted and painful (pathognomonic) |
| Abduction | May be limited |
| Log roll test | Positive (pain with gentle internal/external rotation) |
Comparison with Contralateral Hip
- Always compare to unaffected side
- Reduced range of motion on affected side
Special Tests
| Test | Technique | Interpretation |
|---|---|---|
| Log roll test | Gently roll leg internally and externally | Positive: pain on internal rotation indicates hip pathology |
| FABER test | Flexion, Abduction, External Rotation | Positive: groin pain indicates hip pathology |
| Hip range under fluoroscopy/US | Perform range of motion under imaging guidance if septic arthritis suspected | Effusion visible on ultrasound |
Systemic Examination
- Temperature measurement
- Look for signs of systemic illness
- Examine other joints
- Check for rashes (post-viral exanthems)
First-Line Investigations
| Investigation | Expected Findings in Transient Synovitis | Notes |
|---|---|---|
| Full blood count | Normal or mildly elevated WCC (less than 12,000) | WCC more than 12,000 suggests septic arthritis |
| ESR | Normal or mildly elevated (less than 40 mm/hr) | ESR more than 40 increases septic arthritis probability |
| CRP | Normal or mildly elevated (less than 20 mg/L) | CRP more than 20 concerning for septic arthritis |
| Blood culture | Negative | Obtain if septic arthritis suspected |
| Hip X-ray (AP and frog-leg lateral) | Normal or subtle effusion (widened joint space) | Rules out fracture, SCFE, Perthes |
Imaging
| Modality | Findings | Role |
|---|---|---|
| Plain X-ray | Often normal; may show effusion (widened joint space), compare with contralateral side | Exclude fracture, SCFE, Perthes |
| Ultrasound hip | Effusion present (more than 2mm difference vs contralateral side) | Confirms effusion; guides aspiration if needed |
| MRI | Effusion, synovial thickening; no bone oedema | Reserve for diagnostic uncertainty or persistent symptoms |
Kocher Criteria for Septic Arthritis
| Criterion | Description | Weighting |
|---|---|---|
| 1. Unable to weight bear | Complete inability to bear weight on affected leg | 1 point |
| 2. Temperature more than 38.5°C | Fever at presentation | 1 point |
| 3. ESR more than 40 mm/hr | Elevated inflammatory marker | 1 point |
| 4. WCC more than 12,000/mm³ | Leukocytosis | 1 point |
Predicted Probability of Septic Arthritis (Kocher)
| Number of Criteria | Probability of Septic Arthritis |
|---|---|
| 0 | 0.2% |
| 1 | 3% |
| 2 | 40% |
| 3 | 93% |
| 4 | 99.6% |
Caird Modification (Adding CRP)
| Criterion | Description |
|---|---|
| Original 4 Kocher criteria | As above |
| 5. CRP more than 20 mg/L | Additional predictor |
Adding CRP increases predictive accuracy. CRP more than 20 alone is an independent predictor.
Joint Aspiration
| Indication | When to Aspirate |
|---|---|
| 2 or more Kocher criteria | Consider aspiration |
| 3-4 Kocher criteria | Aspiration mandatory |
| Clinical suspicion of septic arthritis | Aspirate to confirm |
| Diagnostic uncertainty | Aspiration recommended |
| Aspiration Finding | Transient Synovitis | Septic Arthritis |
|---|---|---|
| Appearance | Clear, straw-coloured | Purulent, turbid |
| WCC | Less than 50,000/mm³ | More than 50,000/mm³ |
| PMN percentage | Less than 75% | More than 75% |
| Gram stain | Negative | May be positive (50-75%) |
| Culture | Negative | Positive (60-80%) |
| Glucose | Normal | Low |
For the Orthopaedic Registrar.
1. Indications
- Diagnostic: To rule out Septic Arthritis (Kocher 3/4).
- Therapeutic: To relieve pressure in septic arthritis (though usually requires washout).
2. The Setup
- Setting: Ultrasound suite or Theatre (under GA/Sedation).
- Position: Supine. Hip in neutral or slight abduction.
- Guidance: Ultrasound is Gold Standard. Fluoroscopy if Ultrasound unavailable.
3. The Anterior Approach
- Landmarks: ASIS (Anterior Superior Iliac Spine) and the Femoral Artery.
- Needle Entry: 2-3cm distal and lateral to the intersection of the femoral artery and the inguinal ligament.
- Direction: Aim posteromedially toward the femoral neck.
- Ultrasound: Visualize the fluid pocket (anterior recess). Watch the needle enter the capsule ("Pop").
- Aspiration:
- Dry Tap?: Inject 5ml saline and re-aspirate (Lavage).
- Pus?: Send to Micro immediately. Proceed to Washout.
- Clear?: Send for Cell Count. (WCC >50,000 = Septic).
4. Advanced Microbiology
- Kingella kingae: The "Stealth Bacteria".
- Often confined to the synovium (fluid culture negative).
- Need PCR (16S rRNA) to detect it.
- Responsible for 50% of "Culture Negative" septic arthritis in <4 year olds.
Management Algorithm
CHILD WITH ACUTE HIP PAIN/LIMP
↓
┌─────────────────────────────────────────────────────┐
│ INITIAL ASSESSMENT │
│ - History: onset, fever, preceding illness │
│ - Examination: gait, ROM, internal rotation │
│ - Vitals: temperature │
│ - Does child look well or unwell? │
└─────────────────────────────────────────────────────┘
↓
┌─────────────────────────────────────────────────────┐
│ INVESTIGATIONS │
│ - FBC, ESR, CRP │
│ - Hip X-ray (AP + frog-leg lateral) │
│ - Ultrasound hip (if effusion suspected) │
└─────────────────────────────────────────────────────┘
↓
┌─────────────────────────────────────────────────────┐
│ APPLY KOCHER CRITERIA │
├─────────────────────────────────────────────────────┤
│ 1. Unable to weight bear │
│ 2. Temperature more than 38.5°C │
│ 3. ESR more than 40 mm/hr │
│ 4. WCC more than 12,000/mm³ │
│ (+ Consider CRP more than 20) │
└─────────────────────────────────────────────────────┘
↓
┌─────────────────────────────────────────────────────┐
│ RISK STRATIFICATION │
├─────────────────────────────────────────────────────┤
│ 0 CRITERIA: Low risk (0.2%) │
│ → Likely transient synovitis │
│ → Outpatient management with follow-up │
├─────────────────────────────────────────────────────┤
│ 1 CRITERION: Low-moderate risk (3%) │
│ → Consider observation in hospital │
│ → Repeat bloods 12-24 hours │
├─────────────────────────────────────────────────────┤
│ 2 CRITERIA: Moderate risk (40%) │
│ → Strong consideration for hip aspiration │
│ → Admit for observation │
├─────────────────────────────────────────────────────┤
│ 3-4 CRITERIA: High risk (93-99%) │
│ → Hip aspiration mandatory │
│ → Presumptive septic arthritis until proven │
│ → Emergency surgical drainage if pus aspirated │
└─────────────────────────────────────────────────────┘
↓
┌─────────────────────────────────────────────────────┐
│ MANAGEMENT - TRANSIENT SYNOVITIS │
│ - Rest (bed rest or limited weight bearing) │
│ - Analgesia: NSAIDs (ibuprofen 10mg/kg TDS) │
│ - Discharge with safety netting │
│ - Follow-up in 48-72 hours │
│ - If symptoms persist more than 2 weeks: │
│ → Repeat X-ray to exclude Perthes │
└─────────────────────────────────────────────────────┘
Conservative Management
| Intervention | Details |
|---|---|
| Rest | Relative bed rest for 24-48 hours; limited activity until pain-free |
| Analgesia | Ibuprofen 5-10 mg/kg TDS (max 30 mg/kg/day) or paracetamol 15 mg/kg QDS |
| Hydration | Ensure adequate oral hydration |
| Activity modification | No sports or strenuous activity until symptom-free |
| Follow-up | Review in 48-72 hours; earlier if symptoms worsen |
Medication Summary
| Medication | Dose (Paediatric) | Duration | Notes |
|---|---|---|---|
| Ibuprofen | 5-10 mg/kg TDS (max 30 mg/kg/day) | 5-7 days | First-line NSAID |
| Paracetamol | 15 mg/kg QDS (max 60 mg/kg/day) | As needed | Adjunct or alternative |
| Naproxen | 5-7 mg/kg BD | 5-7 days | Alternative NSAID |
Discharge Criteria
| Criterion | Requirement |
|---|---|
| Low risk (0-1 Kocher criteria) | Yes, can discharge |
| Weight bearing (with limp acceptable) | Yes |
| Afebrile | Temperature less than 38°C |
| Parents understand safety netting | Must verbalize return criteria |
| Follow-up arranged | 48-72 hours review planned |
Safety Netting Advice for Parents
"Bring your child back to hospital immediately if":
- Fever develops or increases
- Your child stops weight bearing completely
- Your child appears more unwell
- Pain is getting worse despite medication
- Symptoms not improving after 5-7 days
Follow-Up
| Timeframe | Action |
|---|---|
| 48-72 hours | Phone or face-to-face review; ensure improving |
| 1-2 weeks | If symptoms persist, examine and consider repeat X-ray |
| More than 2 weeks persistent symptoms | MRI hip to exclude Perthes disease |
Complications of Transient Synovitis
| Complication | Frequency | Notes |
|---|---|---|
| Recurrence | 4-17% | Usually same hip; manageable as per first episode |
| Perthes disease | 1-3% | May develop months later; always follow-up |
| Coxa magna | Rare | Enlarged femoral head following severe effusion |
| Leg length discrepancy | Very rare | Only transient during active inflammation |
Complications of Missed Septic Arthritis
| Complication | Consequence |
|---|---|
| Joint destruction | Irreversible cartilage damage within 24-48 hours |
| Sepsis | Life-threatening systemic infection |
| Growth arrest | Damage to femoral head physis |
| Chronic arthritis | Permanent joint dysfunction |
| Hip instability | Capsular damage |
Key Teaching: Why We Must Not Miss Septic Arthritis
Septic arthritis is an orthopaedic emergency. Delay in treatment leads to:
- Cartilage destruction within hours
- Permanent joint damage
- Need for hip replacement in adulthood
- Potential mortality from sepsis
Natural History
| Outcome | Rate |
|---|---|
| Complete resolution | 99%+ |
| Average duration | 3-10 days |
| Maximum expected duration | 2 weeks |
| Recurrence | 4-17% |
Long-Term Outcomes
| Outcome | Data |
|---|---|
| Full recovery | Virtually all patients |
| No residual hip abnormality | Expected in majority |
| Association with Perthes disease | 1-3% may develop Perthes (controversial) |
| Need for surgical intervention | Rare (only if misdiagnosed) |
Prognostic Factors
| Factor | Prognosis |
|---|---|
| 0 Kocher criteria | Excellent |
| Typical presentation | Excellent |
| Symptom duration less than 1 week | Excellent |
| Persistent symptoms more than 2 weeks | Concerning; investigate for Perthes |
Key Studies
| Study | Year | N | Key Findings | PMID |
|---|---|---|---|---|
| Kocher et al. (Original) | 1999 | 282 | Developed 4-criteria prediction rule; 0/4 = 0.2% septic; 4/4 = 99.6% septic | 10086878 |
| Kocher et al. (Validation) | 2004 | 154 | Validated original criteria; confirmed predictive accuracy | 15167389 |
| Caird et al. | 2006 | 190 | Added CRP more than 20 as fifth criterion; improved specificity | 16818610 |
| Singhal et al. | 2011 | SR | Systematic review confirming utility of Kocher criteria | 21304449 |
| Sultan and Hughes | 2010 | 96 | Low risk of septic arthritis when 0 criteria present; safe outpatient management | 20581327 |
Evidence Summary
| Recommendation | Evidence Level |
|---|---|
| Kocher criteria for risk stratification | High (validated multicentre studies) |
| CRP as additional predictor | Moderate |
| Aspiration if 3-4 criteria | High (guideline consensus) |
| Outpatient management with 0 criteria | Moderate |
| NSAID treatment | Moderate (standard practice) |
Guidelines
| Source | Recommendation |
|---|---|
| BSCOS (British Society for Children's Orthopaedic Surgery) | Kocher criteria risk stratification; low threshold for aspiration if 2+ criteria |
| POSNA (Pediatric Orthopaedic Society of North America) | Similar approach; emphasizes shared decision-making with parents |
| NICE (UK) | General principles; differentiating from serious bacterial infection |
Simple Explanation for Parents
What is transient synovitis? Transient synovitis (also called "irritable hip") is a common condition in children, usually between 3 and 8 years old. It causes pain in the hip and makes your child limp. It often happens after a cold or viral illness.
What causes it? We don't know exactly, but it's probably the body's reaction to a recent virus. The lining of the hip joint becomes inflamed, causing pain and swelling inside the joint.
Is it serious? Transient synovitis itself is not serious and goes away on its own, usually within 1-2 weeks. However, it can look similar to a more serious infection of the hip joint (called septic arthritis), so we need to do some tests to make sure it's not that.
What tests are needed?
- Blood tests to check for infection
- An X-ray of the hip
- Sometimes an ultrasound to look for fluid in the hip
- In some cases, we may need to take a sample of fluid from the hip with a needle
How is it treated?
- Rest: keep your child resting at home until the pain improves
- Pain relief: ibuprofen or paracetamol works well
- Most children feel better within 3-7 days
When should I be worried? Bring your child back immediately if:
- They develop a fever (temperature over 38°C)
- They completely refuse to walk
- The pain is getting worse
- They seem more unwell
- Symptoms don't improve after 7 days
Will it happen again? About 1 in 10 children may have another episode. This is not dangerous but should be checked each time.
-
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. doi:10.2106/00004623-199912000-00002. PMID: 10086878
-
Kocher MS, Mandiga R, Zurakowski D, Barnewolt C, Kasser JR. Validation of a clinical prediction rule for the differentiation between septic arthritis and transient synovitis of the hip in children. J Bone Joint Surg Am. 2004;86(8):1629-1635. doi:10.2106/00004623-200408000-00005. PMID: 15167389
-
Caird MS, Flynn JM, Leung YL, Millman JE, D'Italia JG, Dormans JP. Factors distinguishing septic arthritis from transient synovitis of the hip in children: a prospective study. J Bone Joint Surg Am. 2006;88(6):1251-1257. doi:10.2106/JBJS.E.00216. PMID: 16818610
-
Singhal R, Perry DC, Khan FN, et al. The use of CRP within a clinical prediction algorithm for the differentiation of septic arthritis and transient synovitis in children. J Bone Joint Surg Br. 2011;93(9):1221-1225. doi:10.1302/0301-620X.93B9.26857. PMID: 21304449
-
Sultan J, Hughes PJ. Septic arthritis or transient synovitis of the hip in children: the value of clinical prediction algorithms. J Bone Joint Surg Br. 2010;92(9):1289-1293. doi:10.1302/0301-620X.92B9.24286. PMID: 20581327
-
Luhmann SJ, Jones A, Schootman M, Gordon JE, Schoenecker PL, Luhmann JD. Differentiation between septic arthritis and transient synovitis of the hip in children with clinical prediction algorithms. J Bone Joint Surg Am. 2004;86(5):956-962. doi:10.2106/00004623-200405000-00011. PMID: 15118039
-
Gupta MN, Sturrock RD, Field M. A prospective 2-year study of 75 patients with adult-onset septic arthritis. Rheumatology (Oxford). 2001;40(1):24-30. doi:10.1093/rheumatology/40.1.24. PMID: 11157138
-
Kang SN, Sanghera T, Mangwani J, Skinner JA, Hart AJ. The management of septic arthritis in children: systematic review of the English language literature. J Bone Joint Surg Br. 2009;91(9):1127-1133. doi:10.1302/0301-620X.91B9.22530. PMID: 19721035
-
Pääkkönen M, Peltola H. Acute osteomyelitis in children. N Engl J Med. 2014;370(4):352-360. doi:10.1056/NEJMra1213956. PMID: 24450893
-
Del Beccaro MA, Champoux AN, Bockers T, Mendelman PM. Septic arthritis versus transient synovitis of the hip: the value of screening laboratory tests. Ann Emerg Med. 1992;21(12):1418-1422. doi:10.1016/s0196-0644(05)80053-6. PMID: 1443835
-
Zamzam MM. The role of ultrasound in differentiating septic arthritis from transient synovitis of the hip in children. J Pediatr Orthop B. 2006;15(6):418-422. doi:10.1097/01.bpb.0000228388.32022.7a. PMID: 17001249
-
Nguyen KP, Clement RC, Gartland JJ, Nace J, Grissom LE, Dormans JP. Fluid dynamics of the pediatric hip: implications for optimal timing of septic arthritis imaging and aspiration. Pediatr Emerg Care. 2013;29(4):519-524. doi:10.1097/PEC.0b013e3182919e6e. PMID: 23558267
Common Exam Questions
| Question Type | Example |
|---|---|
| MCQ | A 5-year-old boy presents with limp and hip pain. Kocher criteria: 0/4. What is the most appropriate management? |
| SAQ | List the Kocher criteria and explain how they are used to differentiate transient synovitis from septic arthritis. |
| OSCE | Examine this child's hip. What is your differential diagnosis for a child with acute limp? |
| Viva | Discuss your approach to a 6-year-old with acute hip pain, limp, and low-grade fever. |
High-Yield Viva Points
| Topic | Key Points |
|---|---|
| Kocher criteria | Non-weight bearing, fever more than 38.5°C, ESR more than 40, WCC more than 12,000 |
| Probability with criteria | 0/4 = 0.2%, 4/4 = 99.6% |
| Caird modification | Added CRP more than 20 mg/L as fifth criterion |
| Why we aspirate | To obtain fluid for cell count, Gram stain, culture; to rule out septic arthritis |
| Differentials | Septic arthritis, Perthes, SCFE, osteomyelitis, JIA, malignancy |
| Management of low-risk | Rest, NSAIDs, discharge with safety netting, follow-up 48-72 hours |
| Follow-up if persistent | Repeat X-ray at 2 weeks to exclude Perthes disease |
Common Mistakes
| Mistake | Correct Approach |
|---|---|
| Diagnosing transient synovitis without considering septic arthritis | Always apply Kocher criteria and document risk |
| Sending a well child home with 3-4 Kocher criteria | These children need hip aspiration |
| Not examining internal rotation | Internal rotation is most restricted and most diagnostic |
| Forgetting to follow up | Always arrange follow-up; persistent symptoms may indicate Perthes |
| Missing referred knee pain from hip | Examine hip in any child with knee pain |
Examination Cheat Sheet
| Parameter | Key Information |
|---|---|
| Peak age | 3-8 years |
| Male:Female | 2:1 |
| Aetiology | Post-viral inflammation (URTI in 50%) |
| Duration | 3-10 days |
| Kocher criteria | Non-weight bearing, fever more than 38.5°C, ESR more than 40, WCC more than 12,000 |
| 0/4 criteria | 0.2% septic arthritis risk |
| 4/4 criteria | 99.6% septic arthritis risk |
| Caird addition | CRP more than 20 mg/L |
| Treatment | Rest + NSAIDs (ibuprofen 10 mg/kg TDS) |
| Follow-up | 2 weeks if persistent → exclude Perthes |