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Case 81: Leg deformity

A 25 year old man is brought in by ambulance from a football game. His leg is deformed at the knee and his foot is cool and pale. An xray is shown below.

1. What does the xray show?

Anterior dislocation of the knee.

2. What would be your immediate management?

This is a limb-threatening injury and requires urgent reduction to prevent further traction injury. This can usually be achieved with appropriate sedation in the emergency department.

3. If his foot becomes pink and warm what further investigations would you arrange?

Significant knee injuries such as dislocations may be associated with popliteal artery injuries. These injuries may be complete or partial transections, dissections and intimal injuries. Restoration of perfusion does not exclude injuries to the popliteal artery. The gold standard investigation for arterial injury remains digital subtraction angiography. DSA is obviously invasive and in a limb with normal vascular examination then high quality duplex US scanning is probably the most appropriate screening examination for major arterial injury. CT angiography with modern scanners may be more readily available than trained ultrasonographers.

The key to avoiding major morbidity from missed arterial injury is a high index of suspicion and regular repeat examination of the limb.