A 5-year-old boy presents with a limp and mild hip pain for 3 weeks. X-ray shows increased density of the femoral head with a crescent sign (subchondral lucency). ESR is normal and the child is afebrile. What is the most likely diagnosis?
- A Transient synovitis of the hip
- B Septic arthritis of the hip
- C Perthes disease (Legg-Calvé-Perthes disease) ✓
- D Juvenile idiopathic arthritis
Correct answer: C. Perthes disease (Legg-Calvé-Perthes disease)
Explanation
Perthes disease is avascular necrosis of the femoral head in children aged 4–8 years, more common in boys. The crescent sign (subchondral fracture) on X-ray indicates the fragmentation stage and is pathognomonic. Normal ESR and absence of fever distinguish it from septic arthritis (which is a surgical emergency). Transient synovitis resolves within weeks and does not show X-ray changes. Management depends on age and extent of head involvement.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.