Findings:
Normal ACL is identified in the T1-W (Image 1a), T2-W (Image 2a), and STIR
(Image 3a) datasets.
Discussion:
The normal anterior cruciate ligament (ACL) has a straight, taut appearance
that parallels the roof of the intercondylar notch [Blumensaat’s line]
(Image 4, arrow- ACL, arrowhead- Blumensaat’s line). The normal ACL
is summarized in Table 1.
| Table 1: Normal Anterior Cruciate Ligament |
| -Composed of two distinct bundles - anterolateral and posteromedial -Origin: lateral femoral condyle -Insertion: Anterior aspect of the intercondylar eminence of the tibia -Traverses the lateral aspect of the femoral notch (PCL traverse the medial notch) -12mm in thickness (AP) -Intermediate to hypointense in signal on all sequences -Thinner and less hypointense then the posterior cruciate ligament -ACL commonly buckles or poorly visualized with knee flexion or over- rotation |
Although the T2-W sagittal dataset is the preferred sequence for evaluating the ACL, the coronal and axial images are utilized to confirm or exclude pathology. The femoral attachment, midportion, and tibial attachment are best visualized on the axial, sagittal, and coronal datasets, respectively.
References:
1. Pomeranz S. Gamuts and Pearls in MRI & Orthopedics. MRI-EFI Publications;
1997.
2. Pomeranz S. MRI Total Body Atlas. MRI-EFI Publications; 1992.
