Double PCL sign on sagittal MRI of the knee.

Hadidi O, et al. BMJ Case Rep 2017. doi:10.1136/bcr-2017-222914 Description A 24-year-old male presented with left knee pain and swelling after a fall six weeks earlier playing football. Clinical examination revealed an antalgic gait and a moderate left knee effusion with tenderness along the medial joint line. Anterior drawer and Lachman tests were positive, suggesting an anterior cruciate ligament (ACL) injury. An MRI scan performed shortly after the injury revealed a large joint effusion and significant acute bone oedema involving the medial tibial condyle. While the posterior cruciate ligament (PCL) was intact, the ACL was elongated and suspicious for an intrasubstance tear. A bucket-handle tear of the medial meniscus was observed with the free fragment seen within the intercondylar notch. This gave rise to the double PCL sign on sagittal view. The patient underwent arthroscopic ACL reconstruction with a hamstring graft, and the medial meniscus was excised as it was unrepairable. The ‘double PCL’ sign refers to the anterosuperior displacement of a bucket-handle medial meniscal tear. The torn fragment occupies an anteroinferior position relative to the PCL, producing an apparent second, smaller PCL (figure 1, figure 2). The double PCL sign has been shown to have a high specificity for meniscal tears when noted on MRI. It is important to note, however, that there are normal variants of anatomy—in particular those of the ligaments of Humphrey and Wrisberg—which can give rise to a similar appearance.