The obturator nerve (L2–L4) exits the pelvis through the obturator foramen. A patient with an obturator hernia presents with sensory changes along the medial thigh and knee pain. What is this referred knee pain called, and which branch of the obturator nerve causes it?

• A Hilton's law phenomenon; anterior branch of obturator nerve
• B Howship-Romberg sign; anterior branch of obturator nerve ✓
• C Romberg's sign; posterior branch of obturator nerve
• D Trendelenburg's sign; posterior branch of obturator nerve

Explanation

The Howship-Romberg sign is the classic presentation of obturator hernia: medial thigh and knee pain exacerbated by hip extension and adduction, caused by compression of the anterior branch of the obturator nerve (which carries cutaneous sensation to the medial thigh via the medial cutaneous nerve of thigh, and an articular branch to the knee). Hilton's law states that the nerve supplying a joint also supplies the muscles moving it and the skin over their insertions — this is a separate principle. Trendelenburg's sign indicates gluteus medius weakness.

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

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Written and medically reviewed by the StethoPrep medical team.