Evaluation of the anterolateral ligament of the knee by means of magnetic resonance examination.

OBJECTIVE: To evaluate the presence of the anterolateral ligament (ALL) of the knee in magnetic resonance imaging (MRI) examinations. METHODS: Thirty-three MRI examinations on patients' knees that were done because of indications unrelated to ligament instability or trauma were evaluated. T1-weighted images in the sagittal plane and T2-weighted images with fat saturation in the axial, sagittal and coronal planes were obtained. The images were evaluated by two radiologists with experience of musculoskeletal pathological conditions. In assessing ligament visibility, we divided the analysis into three portions of the ligament: from its origin in the femur to its point of bifurcation; from the bifurcation to the meniscal insertion; and from the bifurcation to the tibial insertion. The capacity to view the ligament in each of its portions and overall was taken to be a dichotomous categorical variable (yes or no). RESULTS: The ALL was viewed with signal characteristics similar to those of the other ligament structures of the knee, with T2 hyposignal with fat saturation. The main plane in which the ligament was viewed was the coronal plane. Some portion of the ligament was viewed clearly in 27 knees (81.8%). The meniscal portion was evident in 25 knees (75.7%), the femoral portion in 23 (69.6%) and the tibial portion in 13 (39.3%). The three portions were viewed together in 11 knees (33.3%). CONCLUSION: The anterolateral ligament of the knee is best viewed in sequences in the coronal plane. The ligament was completely characterized in 33.3% of the cases. The meniscal portion was the part most easily identified and the tibial portion was the part least encountered.