The popliteal fossa contents from lateral to medial are — lateral to medial: common peroneal nerve, tibial nerve, popliteal vein, popliteal artery. In popliteal artery aneurysm, which structure is most likely to be compressed, causing foot drop?

• A Common peroneal nerve as it passes through the popliteal fossa ✓
• B Tibial nerve (medial) — weakness of plantar flexion
• C Common peroneal nerve (lateral, at the fibular neck)
• D Saphenous nerve

Explanation

In the popliteal fossa, the common peroneal nerve runs along the lateral border and is the most superficial structure. A popliteal artery aneurysm expanding posteriorly may compress the common peroneal nerve, causing foot drop (dorsiflexion weakness) and sensory loss over the anterior/lateral leg and dorsum of the foot. The tibial nerve is medial and typically affected only in large aneurysms causing calf pain or plantar sensory loss. The common peroneal also winds around the fibular neck laterally and is vulnerable there to direct pressure.

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

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Written and medically reviewed by the StethoPrep medical team.