The epiphysis of the femoral head appears on radiograph at approximately 4–6 months of age. In Perthes disease (avascular necrosis of femoral head in children), the earliest radiographic sign is:

• A Widening of the joint space (increased medial joint space) ✓
• B Increased density (sclerosis) of the femoral head
• C Fragmentation of the femoral epiphysis
• D Coxa vara deformity

Explanation

The earliest radiographic sign in Perthes disease is widening of the medial joint space due to synovial effusion and cartilage hypertrophy, occurring before avascular changes are visible. Subsequently, the femoral epiphysis appears smaller and denser (sclerosis) due to avascular necrosis. Fragmentation and reossification occur in later stages. Coxa vara is a late deformity. MRI detects avascular necrosis much earlier than plain radiographs.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.