A 30-year-old motorcyclist sustains a posterior dislocation of the knee. Which immediate investigation is mandatory before attempting closed reduction?
- A MRI knee to assess ligament injuries
- B CT angiography or Doppler ultrasonography of the popliteal artery ✓
- C CT arthrogram of the knee
- D Nerve conduction studies for peroneal nerve
Correct answer: B. CT angiography or Doppler ultrasonography of the popliteal artery
Explanation
Knee dislocation (tibiofemoral) carries a 25–50% risk of popliteal artery injury, most commonly by intimal tear causing delayed thrombosis. Vascular assessment with Doppler or CT angiography is mandatory before and after reduction, as even a normal ankle-brachial index (ABI) does not exclude intimal injury. Delayed recognition leads to limb-threatening ischemia. While peroneal nerve and ligamentous injuries are important, they are secondary concerns after vascular assessment.
Reference: Maheshwari Essential Orthopaedics, 6th ed.
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Written and medically reviewed by the StethoPrep medical team.