In brief: Magnetic resonance imaging (MRI) is useful for assessment of capsuloliga-mentous and other periarticular soft-tissue structures of the knee. It is especially valuable for its ability to accurately diagnose tears of the anterior cruciate ligament (ACL). MRI findings that indicate an ACL tear include frank disruption of the ligament, waviness to the anterior margin of the ligament, and areas of heterogeneous increased signal within the ligament on sagittal T2-weighted images.