Diagnostic ultrasound evaluation of posterolateral corner knee injuries

The purpose of this study was to determine whether dynamic ultrasound (US) would be able to differentiate posterolateral corner knee injuries that would require surgical intervention.

This is a single-group cohort study. A knee sonogram was obtained in patients referred to us with suspected posterolateral knee injury. In addition to static US imaging, a dynamic US stress test was performed by placement of maximum varus stress on the knee at 30 degrees of flexion. The tibiofemoral separation was then measured with US. Results from US and surgery were then compared.

Sixteen patients had US and underwent surgery, and twelve patients had surgical findings requiring surgical intervention to the posterolateral knee structures. With regard to static US images, the sensitivity, specificity, negative predictive value, positive predictive value, and accuracy were 92%, 75%, 92%, 75%, and 88%, respectively, for the lateral collateral ligament; 33%, 100%, 100%, 33%, and 50%, respectively, for the popliteus; and 67%, 75%, 67%, 75%, and 69%, respectively, for the popliteofibular ligament. The dynamic US stress test showing 10.5 mm of lateral joint space width or more during varus stress showed a sensitivity of 83% and specificity of 100% for injury to the lateral collateral ligament and posterolateral corner structures, with a positive predictive value of 100%, negative predictive value of 75%, and accuracy of 88%.

A positive dynamic US stress test (>or=10.5 mm) positively predicted the need for posterolateral knee surgery in 100% of patients in this study who required posterolateral corner repair or reconstruction.

Level I, testing of previously developed diagnostic criteria in series of consecutive patients with universally applied gold standard.