Introduction

The anterolateral ligament (ALL) is a relatively new concept of the anterolateral rotational stabilizer of the knee joint. There is still no consensus among scientists on the anatomy of the ALL, and even its existence is questioned by several anatomical studies. What do we actually see on MRI in the area of ALL? How to explain such variability of the ALL intensity, thickness, shape, anatomical structure among the patients? Quite a lot of MRI studies of ALL have already been published. But what do we see on MRI images in these works and in practice?
The aim of the study. The aim was to evaluate ALL variants on MRI images, to summarize their common features and differences, and to try finding an explanation for the phenomenon of the ALL variability.
Materials and methods. ALL were analyzed on 200 series of MRI images obtained from different MRI centers, on MRI scanners from 0.2 to 3 Tesla with the different number of channels and according to different study protocols. The presence of ALL, the number of its layers, the relation to the joint capsule, and other anatomical features were assessed. We associated the rate of identifying these features either with the technical equipment parameters or with anatomical peculiarities.
Results. The anterolateral ligament was visualized on MRI at least partially in 88% of cases. It looked rather variable on MRI images. We have noticed that the increase in the magnitude of the magnetic field plays its role in the frequency of ALL detection, but is more noticeable up to 1.5 Tesla. With an increase in the magnitude above 1.5 Tesla, the quality of ALL visualization increases, but the percentage of its detection does not increase so much. ALL. Axial sections of the high-quality MRI scanners give the opportunity to analyze in sufficient detail the anatomy of separate layers of ALL, their mutual spatial arrangement, and the relationship with the surrounding anatomical structures. However, even the highest quality axial images of the knee joint sometimes raise questions about what we see – ALL or the fascia, joint capsule, or other structure.
Conclusions. The anterolateral ligament is a separate anatomical element of the knee joint that has a variable, but in most cases two-layered, anatomical structure and can be detected on MRI in at least 88% of cases. Improving the quality of MRI scanners and study protocols with a decrease in the interslice intervals in the frontal plane can increase the frequency and quality of imaging of the anterolateral ligament. Axial sections help to identify anterolateral ligament in complex cases and allow analyzing its anatomy but adding little to the diagnosis of the anterolateral ligament injury.