Empty notch sign is a direct sign of anterior cruciate ligament (ACL) tear/avulsion at its femoral attachment. It denotes a fluid signal at the expected ACL attachment site at the intercondylar notch (fossa) on axial and coronal fluid-sensitive MR images.
The proximal ACL is the second most common site of injury after the midsubstance. Hence, close scrutiny of the attachments of the ACL is warranted.
- 1. Tung GA, Davis LM, Wiggins ME, Fadale PD. Tears of the anterior cruciate ligament: primary and secondary signs at MR imaging. Radiology 1993; 188:3. DOI:10.1148/radiology.188.3.8351329