How to read the ACL on a sagittal MRI – and why MRI alone can mislead you On a normal sagittal knee MRI, the ACL appears as a continuous low-signal band running obliquely from the posteromedial aspect of the lateral femoral condyle to the anterior tibial spine. It should be taut, well-defined and parallel to the roof of the intercondylar notch. The PCL, in comparison, is thicker, more vertical and has a smooth curved “parenthesis-like” appearance. In an ACL-deficient knee, the sagittal signs inc