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Patient 3A

A 62-year-old woman twisted her knee two days earlier while moving a sofa at her home. Her pain persisted and she needed a cane to walk.

On examination, the lateral aspect of her knee was tender and there was a small effusion. Flexion was limited to 60°. There was no tenderness over the patella. Her quadriceps strength was good and there was no ligamentous instability.

Patient 3B

A 24-year-old woman was struck on the lateral aspect of her right knee by the fender of a slow moving car and fell to the ground. Swelling of the knee occurred immediately. The patient had no other injuries aside from several minor bruises.

Examination revealed tenderness of the anterior and lateral aspects of her knee. There was a moderate joint effusion and flexion was limited to 45°. There was no ligamentous instability to valgus and varus stress, and the anterior drawer and Lachman tests were normal.

  • Are there any abnormalities on these patients’ knee radiographs (Figures 1 and 2)?
  • What is the most frequently missed radiographically apparent fracture in the ED?

Compared to the wrist and ankle, the radiographic anatomy of the knee is relatively simple and the range of potential fractures is small (Table 1). However, some fractures can have subtle radiographic findings and substantial morbidity if missed.

Table 1 Relative Frequencies of Various Fractures About the Knee in Adult ED Patients

A targeted approach to radiograph interpretation looking for common and easily missed injuries works well for knee injuries. It is more effective and efficient than a systematic approach in which all of the bone contours are traced looking for cortical breaks or deformities.

Most fractures are apparent on the standard AP and lateral radiographs. In some cases, supplementary views are needed to detect an injury. These include: oblique views, an axial patellar (“sunrise”) view, or intercondylar notch (“tunnel”) view (AP view with knee flexed).

Tibial plateau fractures are common, second in frequency only to patellar fractures (Table 1). Markedly displaced fractures can be identified without ...

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