Findings
Coronal (a), sagittal (b,d) & axial (c,e) PDFS images of knee joint reveal chronic complete tear of anterior cruciate ligament (ACL) with fluid signal at femoral attachment site (e) giving appearance of empty notch sign. Bucket handle tear of medial meniscus is seen with displacement of meniscal fragment into the intercondylar notch (a,c). Complex tear of body, posterior horn of lateral meniscus having both horizontal, longitudinal components reaching superior, inferior articular surfaces with flipping of posterior horn posterior to anterior horn is seen (b). Mild effusion is seen in knee joint cavity and suprapatellar recess. The double posterior cruciate ligament (PCL) sign is seen in image d.
Diagnosis
- Complete ACL tear
- Bucket-handle tear of medial meniscus and complex lateral meniscal tear with flipped meniscus
Summary
Empty notch sign is a direct sign of ACL tear/avulsion at its femoral attachment. The double PCL sign is seen on midline sagittal MR images of the knee as a low signal-intensity band that is parallel and anteroinferior to the PCL. The double PCL sign is associated with bucket-handle tears of the medial meniscus that occur in the presence of an intact anterior cruciate ligament (ACL). A bucket-handle tear is a longitudinal tear of a meniscus that results in a displaced but attached meniscal fragment. A double posterior cruciate ligament sign from a torn medial meniscus can essentially only be seen in patients who have an intact ACL as this is required to prevent the flipped fragment from migrating further laterally, or not aligning parallel to the PCL. In a minority of patients, a lateral meniscus bucket handle tear, in the presence of torn anterior cruciate ligament, may also give rise to a double posterior cruciate ligament sign. A flipped meniscus is a sub-type of bucket-handle tear where a large portion of meniscus flips to lie adjacent to the anterior horn leaving an empty space at the donor site.
Further reads
- Camacho M. A. (2004). The double posterior cruciate ligament sign. Radiology, 233(2), 503–504. https://doi.org/
- https://radiopaedia.org/articles/empty-notch-sign-anterior-cruciate-ligament-tear
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