The (deep) lateral femoral notch sign describes a depression on the lateral femoral condyle at the terminal sulcus, a junction between the weight bearing tibial articular surface and the patellar articular surface of the femoral condyle.
The likely mechanism is a hyperextension or impaction injury with a collision of the femoral condyle and the posterior tibial plateau during the rotational movement responsible for injuring the ACL, most commonly the pivot-shift.
Lateral femoral notch sign is usually first appreciated on the lateral radiograph and is suggestive of an osteochondral fracture 1-2. The depth of the lateral femoral notch sign has been shown to correlate with anterior cruciate ligament (ACL) tear 2.
A normal sulcus is located is located within 10mm of Blumensaat's line on lateral projection 3.
On a lateral projection, a line is drawn from the normal articular surface of the lateral femoral condyle. The depth of the abnormal depression/notch can then be measured. A study compared the depth of the lateral femoral notch in patients with proven ACL tear and healthy individuals. A notch depth of 1.5 mm is shown as a useful additional sign of a torn ACL 2.
Internal derangement should also be suspected if the notch is irregular.
- 1. Pao DG. The lateral femoral notch sign. Radiology. 2001;219 (3): 800-1. Radiology (citation) - Pubmed citation
- 2. Cobby MJ, Schweitzer ME, Resnick D. The deep lateral femoral notch: an indirect sign of a torn anterior cruciate ligament. Radiology. 1992;184 (3): 855-8. Radiology (citation) - Pubmed citation
- 3. Warren RF, Kaplan N, Bach BR, The lateral notch sign of anterior cruciate ligament insufficiency. Am J Knee Surg, 1988;1:119-24.