Empty notch sign (anterior cruciate ligament tear)

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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.