- Transient synovitis of the hip = self-limiting inflammation of the synovium.
- Most common cause of acute hip pain in children.
- Diagnosis of exclusion — must differentiate from septic arthritis.
Epidemiology
- Incidence: ~3% of children aged 3–10 years.
- Peak age: 4–8 years.
- Sex ratio: M:F = 2:1.
- Recurrence: Up to 20%.
Aetiology & Risk Factors
- Exact cause unknown, but associated with:
- Viral infection (e.g. URTI)
- Post-streptococcal reaction
- Trauma
- Allergic response
- Elevated interferon levels
Pathophysiology
- Nonspecific inflammation and hypertrophy of synovial membrane.
- Results in joint effusion and mild symptoms.
Clinical Presentation
History
- Recent URTI or trauma
- Acute or gradual groin/thigh pain
- Refusal to weight-bear
- Symptoms often improve during the day
Symptoms
- Mild or no fever
- Limping
- Muscle spasm
Examination
- Hip held in FABER position (flexion, abduction, external rotation)
- ↓ Internal rotation = most sensitive finding
- Generally non-toxic appearance
- Log roll test → involuntary guarding
- Non-tender lumbar spine/knee
Investigations
Imaging
- X-ray: Often normal, AP + frog-leg views
- USS: May show joint effusion, synovial thickening
- MRI: If suspect osteomyelitis or myositis
Labs
- CRP <20 mg/L → helps exclude septic arthritis
- ESR <20 mm/hr, WCC slightly raised
- Joint aspirate: WBC >50,000 = assume septic arthritis
Differential Diagnoses
- Septic arthritis of hip
- Osteomyelitis
- SCFE (Slipped Capital Femoral Epiphysis)
- Perthes disease
- Neurological disorders
Management
Non-operative
- NSAIDs (oral or IV) + observe for 24 hrs
- Minimise weight-bearing
- Traction may help with rest
- No antibiotics unless septic arthritis suspected
Diagnostic clue:
- Improvement with NSAIDs = more likely transient synovitis
Prognosis
- Usually benign
- Most resolve in 1–2 weeks
- Marked improvement in 24–48 hours
- Recurrence in ~20%
Complications
- Legg-Calvé-Perthes disease – controversial link (0–10% in series)
- Rarely leads to long-term issues
Related