Ligamentous structures of the knee are numerous and complex, including the anterior and posterior cruciate ligaments, medial and lateral collateral ligaments, ligaments of the posteromedial and posterolateral corners, and the anterolateral ligament. Clinical assessment after a knee injury is paramount and can direct both the clinician's choice of imaging study and the radiologist's interpretation. Imaging is crucial in that it provides additional information for diagnosis, management, and surgical planning. Multiple imaging modalities can be used in the evaluation of the knee injuries, with radiographs an important baseline study, magnetic resonance imaging as the best tool for a comprehensive assessment including cruciate ligament evaluation, and ultrasound useful in evaluating superficial structures. Knowledge of both normal and pathological appearances of ligamentous structures, as well as typical injury patterns, is useful not only for radiologists but also for clinicians who manage patients with knee pain.