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).^[1][2] It is an abnormal deepening of the lateral condylopatellar sulcus from an osteochondral impaction fracture.^[1][3] A depth greater than 1.5 mm (0.059 in) is a reliable sign of a torn ACL.^[1]

Deep lateral femoral notch sign

Measurement technique to determine the depth of the femoral notch on lateral x-rays