Magnetic resonance imaging‐based identification of the knee anterolateral ligament: A systematic review with meta‐analysis

Abstract Purpose The anterolateral ligament (ALL) is recognised as a stabiliser against internal tibial rotation and as a supporting structure for the anterior cruciate ligament; however, its MRI appearance is inconsistently reported. This systematic review and meta‐analysis aimed to synthesise the current literature to provide evidence regarding the visualisation, morphometry and injury prevalence of the ALL on magnetic resonance imaging (MRI). Methods A systematic review of PubMed, Google Scholar, Scopus and Web of Science was conducted in accordance with preferred reporting items for systematic reviews and meta‐analyses guidelines. Eligible studies reported the MRI visualisation and/or anatomical characteristics of the ALL. Pooled prevalence and means were calculated using random‐effects models. Subgroup analysis and meta‐regression were performed to identify factors affecting visualisation. Results Twenty‐six studies comprising 2706 knees were included. The pooled prevalence of ALL visualisation was 92.96% (95% CI: 87.81–96.91). Complete visualisation of the entire ligamentous course was achieved in 56.03% (95% CI: 37.39–73.86), while partial visualisation was 38.34% (95% CI: 27.90–49.32). Visibility was highest for the tibial part (80.91%) and lowest for the meniscal part (66.83%). Nationality ( p < 0.001) and knee flexion ( p = 0.0144) significantly influenced visualisation. Pooled morphometric means were length of 34.09 mm, width of 6.32 mm and thickness of 1.17 mm. Lastly, the pooled prevalence of concomitant ALL injury (with anterior cruciate ligament injury) was 35.63% (95% CI: 20.26–52.60). Conclusion Pooled evidence suggests a high reported prevalence of ALL visualisation on MRI. However, considerable heterogeneity indicates that reproducibility across different protocols remains uncertain. While technical factors such as knee flexion and multiplanar assessment appear to enhance ALL identification, standardised radiological criteria are necessary to definitively distinguish the ALL from the adjacent joint capsule. Level of Evidence Level III.