Anterolateral ligament of the knee. Review of current concepts
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In recent years, there has been great interest in a structure located in the anterior and lateral regions of the knee due to its potential contribution to rotational stability. This structure has been termed the anterolateral ligament. To date, anatomical, histological, imaging, and biomechanical studies have been conducted on the subject. The purpose of this review is to summarize the publications on this ligament published between 2007 and 2015. Databases were searched for articles in English and Spanish that mentioned the anterolateral ligament of the knee. A total of 27 articles in English were found, of which 24 were original articles, 2 editorial letters, and 1 poster presentation. The anterolateral ligament of the knee is a real structure, independent of the joint capsule and the popliteus tendon, which is present in most patients. It appears to complement the stabilizing functions of the anterior cruciate ligament, as its tension increases when the knee is flexed and internally rotated.
Assessing the function of a healthy knee that only shows a very mild pathological tendency is a task that requires experience and a trained clinical eye. Understanding the function of the ALL helps us focus on that area and the knee’s overall behavior. A comprehensive approach that addresses all the factors of the pathology and the individual patient’s needs is essential for successful and, above all, long-term treatment.
We summarize the conclusions of the study:
Biomechanics
Parsons et al. performed a study on 11 cadaveric knees, to which they applied an anterior drawer force of 134 N at flexion angles between 0 and 90°, and an internal rotation of 5 N m at the same flexion angles. They determined the in situ forces of the ALL, ACL, and LCL using the superposition principle. They showed that the contribution of the ALL during internal rotation increased considerably with increasing knee flexion, while that of the ACL also decreased. During the anterior drawer, the ALL forces were considerably lower compared to the ACL forces at the different flexion angles. Based on this information, they concluded that the ALL is an important stabilizer of internal rotation at flexion angles greater than 35° and that, therefore, damage to this ligament can generate knee instability at high flexion angles, which is why a positive pivot sign can be observed in some patients with an intact ACL but an affected ALL. Conclusions
According to various studies published between 2007 and the present, the anterolateral ligament of the knee can be considered a real structure, independent of the joint capsule and the popliteus tendon, which is present in most patients. However, it exhibits anatomical variations, especially at its femoral origin. Histological analyses confirm the presence of ligamentous tissue, albeit with microscopic variations along its course.
It can be visualized in both ultrasound and magnetic resonance imaging, although no specific imaging protocol has been reported for its clinical evaluation. According to studies published since 2007, the mean length is 41.1 mm; the width is 6.9 mm; and the thickness is 1.9 mm.
The ligament appears to complement the stabilizing functions of the anterior cruciate ligament, as its tension increases when the knee is flexed and internally rotated.
- – The anterolateral ligament of the knee is a critical structure for joint stability. It is important to continue researching it to expand anatomical knowledge and therapeutic options for patients with knee ligament injuries who do not improve after appropriate treatment.