Review Question - QID 218178

The MRI demonstrates a "double PCL sign," indicative of a bucket handle medial meniscus tear which would lead to a locked knee and inability to perform passive or active terminal extension.

Meniscus tears are one of the most common knee injuries seen by orthopedic surgeons and may present in multiple ways. They typically present with joint line pain specific to the meniscus injured but may also produce mechanical symptoms like locking or catching of the knee. In cases where there is a large bucket handle meniscus tear that displaces into the joint, patients can lose the ability to terminally extend the knee. Patients with meniscus tears also typically have an effusions and may respond to other provocative testing such as a McMurray or Thessaly test. MRI is indicated in cases where mechanical symptoms are present or if the knee is locked. In cases of medial meniscus bucket handle tearing, the MRI will show a "double PCL sign," where the normal triangular appearance of the posterior meniscal horn is absent but the displaced fragment is seen more anteriorly within the joint.

Hamada et al. discussed the change of signal intensity of the displaced medial meniscus on MRI after its reduction. They noted that after the reduction of the meniscus the signal intensity when from high to low. They concluded that high signal intensity on initial MRI should sway surgeons from repairing the meniscus, as this will usually change after appropriate reduction.

Alatakis and Naidoo provide an overview of MRI evaluation of meniscal and cartilage injuries of the knee. They talk about different variations of meniscal tearing and how to identify them on MRI, including bucket handle tearing. Additionally, they review the evaluation of articular cartilage injuries and the best sequences to identify them on MRI.

Figures A & B are coronal and sagittal MRI sequences demonstrating a "double PCL sign," with the torn medial meniscus flipped into the intercondylar notch.

Incorrect Answers:
Answer 1: This describes the pivot-shift maneuver where the IT band becomes taut and causes reduction of the lateral tibial plateau underneath the lateral femoral condyle. A positive pivot-shift maneuver is indicative of an ACL tear.
Answer 2: This describes the quadriceps activation test, which is positive in cases of PCL rupture where the tibia is subluxed posteriorly until the quadriceps is fired.
Answer 4: Excessive lateral patellar translation, a J-sign, and an effusion are indicative of an episode of lateral patellar dislocation.
Answer 5: Posterior tibial sag sign occurs with posterior translation of the tibia in relation to the femur.