II. Etiology
- Idiopathic
III. Epidemiology
IV. Pathophysiology
- Inflammatory Arthritis of the hip
V. Symptoms
- Follows 3-6 days after Upper Respiratory Infection
VI. Signs
-
Hip Pain
- Pain radiates to anteromedial thigh and knee
- Reduced Hip Range of Motion
- Hip typically held in position of comfort (hip flexed, abducted and externally rotated)
- Guarded hip rotation in Transient Synovitis (but will tolerate passive range of motion testing)
- Will bear weight on joint enough to demonstrate a limp
- Contrast with Septic Arthritis with more pronounced spasm, guarding, and fixed position with a refusal to bear weight
-
Fever
- Low grade fever may be present (under 39 C or 101 F)
- Contrast with Septic Arthritis with higher Temperature and associated systemic symptoms (e.g. malaise)
VII. Labs
- Complete Blood Count with differential
- Acute phase reactants: Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (C-RP)
- ESR and C-RP will be normal or only slightly elevated in Transient Synovitis
- Contrast with Septic Arthritis in which ESR >25 mm/h (>40 is highly suggestive) and C-RP >20 mg/L
- Joint aspirate (typically by orthopedics or radiology)
- Hip Synovial Fluid clear
VIII. Imaging
-
Hip XRay
- Bony landmarks normal
- No signs of Fracture or defect
- Rules out serious hip disease
- Aseptic necrosis
- Osteomyelitis
- Increased space between acetabulum and femoral head
- Bony landmarks normal
- Hip, Pelvis, femur, tibia-fibula and foot XRay
- Consider in children where the source of pain and limp is unclear
-
Hip Ultrasound
- Demonstrates joint effusion (>2-5 mm) in >50% of cases
- Joint effusion on Ultrasound requires joint aspirate to differentiate from septic hip
- Hip MRI
- Consider in non-diagnostic Ultrasound (no effusion), but higher suspicion for septic hip
IX. Diagnosis: Kocher's Decision rule - 4 Criteria
- Findings suggestive of Septic Arthritis (Mnemonic: Walk FEW)
- Fever >38.5 C (101.3 F)
- Inability or refusal to bear weight
- Erythrocyte Sedimentation Rate >40 mm Hg
- White Blood Cell Count >12,000/mm3
- Interpretation of 4 critreria rule
- All 4 factors absent rules out Septic Arthritis (Test Sensitivity 99.8%)
- One predictor present: 3% risk of septic hip
- Two predictors present: 40% risk of septic hip
- Three predictors present: 93% risk of septic hip
- All 4 factors present strongly suggests infection (60-98% likelihood of septic hip)
- Modifications
- C-Reactive Protein (C-RP) >20 mg/L (or 2 mg/dl) has been included as a fifth factor criteria
- References
X. Diagnosis: Decision rule - 2 Criteria
- Findings suggestive of Septic Arthritis
- Inability or refusal to bear weight
- C-Reactive Protein (C-RP) >20 mg/L (or 2 mg/dl)
- Interpretation
- Both factors absent: <1% probability of Septic Arthritis
- Both factors present: >74% probability of Septic Arthritis
- References
XI. Differential Diagnosis
- See Pediatric Limp Causes
-
Septic Arthritis of the hip
- Keep high index of suspicion
- See Signs and Diagnosis above
- Legg-Calve-Perthes Disease
XII. Evaluation: Red Flags suggestive of Septic Arthritis of the hip
- Fever (esp. >101.3 F or 38.5 C)
- Toxic appearance
- Pain with Hip Range of Motion in any direction
- Refusal to bear weight
- Erythrocyte Sedimentation Rate >40 mm/hour
- C-Reactive Protein >20 ml/L
XIII. Evaluation: Emergency Department Approach
- See Limping Child
- Obtain initial basic studies (XRay, labs and consider Bedside Ultrasound)
- Consider giving NSAIDs in Emergency Department
- If child is walking after Ibuprofen and is non-toxic in appearance, may typically disposition home
- Toxic appearing, febrile, non-ambulatory child
- Obtain formal Ultrasound and if non-diagnostic (no effusion), then obtain MRI
- Admit and obtain orthopedic Consultation
- Non-toxic, febrile non-ambulatory child
- If labs, XRay are reassuring and child is well-appearing, disposition home with follow-up
- If labs positive or non-well appearing, obtain Ultrasound (consider MRI if non-diagnostic Ultrasound)
- Consider Pediatric Limp Causes
- Non-toxic, affebrile, non-ambulatory child
- If XRay non-diagnostic, obtain labs and if positive, then obtain Ultrasound
- Consider Pediatric Limp Causes
- References
- Orman and Horezcko in Herbert (2017) EM:Rap 17(5): 13-4
XIV. Precautions
- When higher clinical suspicion, fully exclude septic hip (u/s, MRI, hip Joint Aspiration) regardless of Kocher Criteria
XV. Management
- Non-weight bearing on affected leg
- Bed rest for 2 to 3 days
-
NSAIDs
- May speed up recovery time
- Also offers Analgesic effect
- Failure to improve with NSAIDs should prompt reconsideration of differential diagnosis
- Kermond (2002) Ann Emerg Med 40:294-9 [PubMed]
XVI. Course
- Transient Synovitis usually clears within 7 days
XVII. Complications
- Legg-Calve-Perthes Disease occurs in 1-3% of cases
XVIII. References
- Jhun and Raam in Herbert (2016) EM:Rap 16(2):15-6
- Claudius and Behar in Majoewsky (2012) EM:RAP-C3 2(8): 1
- Sawyer (2009) Am Fam Physician 79(3):215-24 [PubMed]