Deep lateral femoral notch sign

In radiology, the deep lateral femoral notch sign is a finding on a lateral radiograph that is considered an indirect sign of a torn anterior cruciate ligament (ACL). It appears as an abnormal deepening of the lateral condylopatellar sulcus. The deepened depression of the lateral condylopatellar sulcus is attributed to an osteochondral impaction fracture. A sulcus depth that is greater than 1.5 mm is considered a relatively reliable sign of a torn ACL.