Objective: The aim of our study was to determine inter-observer agreement in the ultrasonographic identification of the anterolateral ligament (ALL) and in the evaluation of its length and thickness in healthy subjects.
Methods: 80 healthy volunteers (160 knees) (42 males and 38 females) were enrolled in the study. All subjects underwent ultrasound (US) examination of both knees, performed by two physicians with over ten years of musculoskeletal US experience. In order to keep the ALL under optimal tension, the knee was flexed at approximately 30-35°, slightly internally rotated and length and thickness of the ligament were measured.
Results: ALL was identified in 93.8% (150 out of 160) and in 92.5% (148 out of 160) of the knees by Evaluator 1 and Evaluator 2, respectively. Interobserver agreement was substantial to almost perfect for the visualization of the ALL ( =0.90) and for measurements of its length (ICC = 0.83), and strong for measurements of its thickness (ICC = 0.75).
Conclusion: In our study on healthy subjects, ALL has been visualized with a high rate of reproducibility. Further studies are needed to see if US may be a reliable and reproducible diagnostic tool in patients with traumatic or degenerative knee disorders.
Level of evidence: II, evidence obtained from cohort study.
Keywords: anatomy; anterolateral ligament; knee; ultrasound.