MRI features of the anterolateral ligament of the knee

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

Materials and methods: 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.

Conclusions: 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.

Results: 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.