MRI features of the anterolateral ligament of the knee

Evaluate the visibility and describe the anatomical features of the anterolateral ligament of the knee using MRI.

Magnetic resonance imaging examinations of the knee were independently reviewed by two musculoskeletal radiologists and assessed for the visibility of the anterolateral ligament under direct cross-referencing of axial and coronal images as complete, partial, or non-visible. Distal insertion site (tibial, meniscal), distance to lateral tibial plateau, measurements (length, width, thickness), and associated imaging findings were also tabulated. Clinical and surgical records were also reviewed.

Seventy MRI scans from 60 consecutive subjects were included in the study. Mean age was 40 years, body mass 74.9 kg, and height 1.72 m. The subject population was 53 % male, most of the knees were from the left side (51 %), and chronic pain was the main clinical symptom (40 %). Nine knees (13 %) had undergone previous surgery. The anterolateral ligament was identified in 51 % of the knees: completely visible in 11 % and partially visible in 40 %. In all visible cases, the distal insertion site was identified on the tibia, with a mean distance of 5.7 mm to the plateau. A completely visible ligament had a mean length of 33.2 mm, thickness of 5.6 mm, and width of 1.9 mm. Inter-observer agreement for ligament presence was significant (κ = 0.7). Statistical analyses showed a trend to be more visible in men, with a longer length compared with women.

Magnetic resonance imaging clearly identifies the anterolateral ligament of the knee in slightly more than half of cases, being partially visible in most of them. In all cases, a tibial insertion is characterized.