The lateral notch sign associated with acute anterior cruciate ligament disruption.

We prospectively studied all of the patients with anterior cruciate ligament disruptions who sought treatment at the senior author's office during a 36-month period. Plain radiographs identified depressions measuring 2 mm or more in the lateral femoral condyle (lateral notch sign) in 9 of 120 knees (7.5%) with acute anterior cruciate ligament disruption and in 2 of 44 knees (4.5%) with chronic pivot shift instability. The depression ranged from 2 to 6 mm deep and from 20 to 25 mm long. The mean age for acutely injured patients with lateral notch signs was 17.2 years, 6 years younger than the mean age of the group with acutely injured anterior cruciate ligaments as a whole. Ten of the 11 patients (91%) with lateral notch signs were men, and all 6 patients with depressions shallower than prior descriptions of the notch sign were men. In contrast, 67% (N = 110) of the entire group of patients who had anterior cruciate ligament disruption were men. Ten of the 11 patients (91%) with the lateral notch signs and 4 of the 6 patients (66%) with minimal depressions also had lateral meniscus tears, while 58 of 147 patients (39%) without lateral femoral condyle depression had lateral meniscus tears. Previous reports that the lateral notch is a sign of chronic anterior cruciate ligament deficiency with recurrent pivot shifts are not supported by the number of prospectively recognized acute lateral femoral notch signs in this series. We found the presence of radiographic changes in the lateral femoral condyle to have statistically significant correlations with young age, male sex, lateral meniscus tears in general and anterior-horn lateral meniscus tears specifically, and lateral femoral chondral lesions.