PROBLEM
An 11-year-old boy has injured his knee in a fall. What is your interpretation of these frontal and lateral views of his knee?

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ANSWER
The correct diagnosis is avulsion of the anterior tibial spine (arrows). This injury is associated with rupture of the anterior cruciate ligament. The lateral view shows a large effusion within the joint. This fracture is more commonly seen in children.

This series of diagnostic quizzes that challenge your ability to read a variety of x-ray films is edited by Dr. Keats, alumni professor of radiology at the University of Virginia School of Medicine in Charlottesville.

Emerg Med 38(12):65-6, 2006