🧸 Always consider if there is any Non-accidental injury and safeguarding issues — a painful or reluctant child must always be assessed in context. ⚠️
🦴 About
- A relatively common but anxiety-provoking presentation in children, often seen in ED and general practice. The challenge lies in distinguishing benign transient synovitis from serious pathology such as septic arthritis or SUFE.
🧬 Aetiology (Age-related Patterns)
| 👶 Age | 🧠 Causes |
|---|
| 0–4 years | Septic arthritis, Developmental dysplasia of the hip (DDH), Transient synovitis |
| 5–10 years | Septic arthritis, Perthes disease, Transient synovitis |
| 10–16 years | Septic arthritis, Slipped upper femoral epiphysis (SUFE), Juvenile idiopathic arthritis (JIA) |
🔍 Causes Explained
- 🦠 Septic arthritis: True orthopaedic emergency — untreated infection can destroy the joint. Differentiation from transient synovitis is vital.
- ⚫ Perthes disease: Idiopathic avascular necrosis of the femoral head; typically 4–10 yrs (peak 5–7), 4× more common in boys, bilateral in 10%.
- ⚖️ Slipped Upper Femoral Epiphysis (SUFE): Posteroinferior displacement of femoral head, usually 11–14 yrs; common in obese boys, bilateral in 20–40%.
- 🌿 Transient synovitis vs septic arthritis: Both cause limp, hip/groin pain, and low-grade fever — Kocher criteria help risk-stratify.
- 🦴 Osteomyelitis: May involve proximal femur/pelvis; pain ± fever; passive motion often preserved if not intra-articular.
- 🔥 Juvenile idiopathic arthritis (JIA): Chronic inflammatory disease; hip involvement bilateral in 30–50%.
🩺 Clinical Features
- Groin, thigh, or knee pain (referred from hip pathology).
- Limp or refusal to bear weight.
- Swelling, warmth, or reduced movement of the hip.
- Systemic features — fever, malaise, irritability.
🧍♂️ Hip Movement Ranges
- Active: Flexion 120–135°, Extension ≈ 30°, Abduction 45–50°, Adduction 20–30°.
- Passive rotation: Internal + external ≈ 90°.
Internal rotation ↑ with femoral anteversion (common in younger children), which decreases with age (~30° → 15° by adolescence).
🚨 Red Flags
- Infant < 3 yrs with painful joint.
- Fever, night sweats, weight loss, anorexia.
- Nocturnal pain, stiffness, or swelling.
- Systemic illness or toxic appearance.
🔬 Investigations
- 🧫 Bloods: FBC, ESR, CRP, U&E, Ca, Mg, LFTs, blood cultures.
- 📈 Raised CRP/ESR → suggests infection or inflammation.
- 🩻 Imaging:
- X-ray (AP + frog-leg) — assess for SUFE or Perthes.
- Ultrasound — detect effusion (septic arthritis vs transient synovitis).
- MRI — osteomyelitis or early avascular necrosis.
- Bone scan — localises infection or stress fracture.
⚕️ Management Overview
- 🚑 Urgent orthopaedic referral for any child < 3 yrs or > 9 yrs with acute hip pain or inability to weight-bear.
- 🦠 Suspected septic arthritis → immediate aspiration and IV antibiotics.
- 💤 Transient synovitis → rest + NSAIDs + reassess after 48 h.
- 🏥 SUFE → non-weight-bearing + urgent fixation.
- 🔁 Ongoing follow-up for Perthes or JIA under paediatric orthopaedics/rheumatology.
📚 References
💡 Teaching tip:
In a limping child, always ask: “Is it infection, is it SUFE, or is it transient synovitis?”
Remember the mnemonic “STOP JOG” — Septic arthritis, Transient synovitis, Osteomyelitis, Perthes, JIA, Overuse injury, Growth plate slip. 🏃♂️
