Ultrasonographic Identification of the Anterolateral Ligament of the Knee

Purpose: To determine ultrasonography's sensitivity for identifying the anterolateral ligament (ALL). Methods: A descriptive study of 18 cadaveric knees was performed. Ultrasonography was used to locate any anterolateral structures at the knee that could correspond to the ALL. The structure's length and relation with other notable anatomic landmarks (fibular head, Gerdy tubercle, joint line, lateral femoral epicondyle, popliteus tendon insertion) were quantified. The ultrasonography measurements were validated by dissecting each knee. The sensitivity of ultrasonography for detecting the ALL and the agreement between the ultrasonographic and cadaveric measurements (Cohen kappa) were determined by statistical analysis. Results: The ALL was found in all 18 cadaveric knees and corresponded anatomically to the ultrasonographic descriptions. Ultrasonography had 100% sensitivity for detecting the presence of the ALL. The ALL's insertion on the lateral femoral condyle was, on average, 12.08 mm (SD, 4 mm; range, 7 to 15 mm) proximal and posterior to the lateral femoral epicondyle and 20.5 mm (SD, 3 mm; range, 16 to 24 mm) proximal to the middle of the popliteus tendon insertion. The ALL inserted onto the tibia, midway between the Gerdy tubercle and the fibular head; the distance between the midpoint of the tibial insertion and middle of the Gerdy tubercle was 19.05 mm (SD, 2.1 mm; range, 15 to 25 mm), and the distance was 19.13 mm (SD, 2.3 mm; range, 14 to 23 mm) to the tip of the fibular head. The agreement between the ultrasonographic and cadaveric findings was excellent (Cohen kappa coefficient between 0.88 and 0.94). Conclusions: Ultrasound imaging is a suitable tool for identifying the ALL of the knee, and it allowed for a detailed analysis of the entire ALL in all 18 knees. However, its ability to evaluate any injuries to the ALL must still be shown.