A 13-year-old overweight boy complains of left hip pain and a limp. Pelvic radiograph shows that a line drawn along the superior aspect of the femoral neck does not intersect the epiphysis of the affected hip. What is the diagnosis?

• A Legg-Calve-Perthes disease
• B Developmental dysplasia of the hip
• C Slipped capital femoral epiphysis ✓
• D Transient synovitis of the hip

Explanation

Klein's line drawn along the superior femoral neck normally intersects the lateral portion of the capital femoral epiphysis. Failure of the line to intersect the epiphysis, called Trethowan sign, indicates superior or medial slip of the epiphysis, which is slipped capital femoral epiphysis. This typically affects obese adolescents around puberty. In Perthes disease the epiphysis is flattened and fragmented but remains aligned within Klein's line in early stages.

Reference: Grainger and Allison's Diagnostic Radiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.