Stress Radiographs for Ligamentous Knee Injuries

Stress radiographs can provide an objective, quantifiable assessment of ligamentous knee injury. Commonly utilized techniques include varus, valgus, and posterior stress radiographs and can be used to augment findings on physical examination and magnetic resonance imaging. Both in vitro and in vivo studies have demonstrated reliability and validity of stress radiographs for diagnosing isolated and multiple ligament knee injuries. Varus stress radiographs are clinician applied at 20° flexion to detect injuries to the fibular collateral ligament and posterolateral corner. Valgus stress radiographs are clinician applied at 20° flexion to detect injuries to the medial collateral ligament or posteromedial corner. To evaluate the posterior cruciate ligament, posterior kneeling stress radiographs are obtained with the patient kneeling at 90° flexion on a firm platform. Bilateral radiographs are obtained and the side-to-side difference is compared to established criteria for injury severity. Stress radiographs support accurate diagnosis of complex knee injuries and also provide an objective measure of knee stability following ligament reconstruction. These imaging techniques can be performed in an ambulatory clinic setting with minimal additional equipment, and are thereby cost-effective, efficient, and support clinical decision-making in the treatment of complex knee injuries.