Presentation
Post-traumatic knee locking and swelling with suspicion of ACL tear.
Patient Data
High-grade ACL tear involving the mid-part of the ACL, with malalignment of the ACL, which appears slightly less vertical than normal. Bone marrow edema of the anterolateral aspect of the lateral femoral condyle and posterolateral aspect of the lateral tibial plateau, representing pivot-shift injury. Anterior tibial translation is noted (about 7.5 mm). Bone marrow edema of the medial femoral condyle and medial tibial plateau is also noted (contrecoup injury).
Complex tear of the posterior horn of the medial meniscus (horizontal tear with vertical tear reaching the superior articular surface).
There is a longitudinal vertical meniscal tear extending from the junction of the ligament of Wrisberg with the posterior horn of the lateral meniscus to the posterior horn of the lateral meniscus, representing Wrisberg rip.
Horizontal fracture of the upper tibia, mainly laterally.
Signs of muscle injury of the medial head of gastrocnemius muscle, manifested by intramuscular edema and minimal surrounding fluid.
Large amount of joint effusion.
Medial patellar plica is noted.
A superior tibio-fibular small cyst is noted.
A small PCL ganglion cyst is noted.
Case Discussion
It is important to differentiate between Wrisberg rip and Wrisberg pseudotear, as the Wrisberg rip is seen as a high signal of the posterior horn of the lateral meniscus which extends from the junction of the ligament of Wrisberg (as in our case), however the Wrisberg pseudotear is usually seen as an intermediate signal between the ligament of Wrisberg and the posterior horn of lateral meniscus, without meniscal extension. Wrisberg tear can be considered as a second sign of anterior cruciate ligament injury, as it only occurs in association with ACL tears.
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