The anterolateral ligament (ALL) has been proposed as a secondary stabilizer of the knee against tibial internal rotation in anterior cruciate ligament (ACL)-deficient knees. The deep lateral femoral notch sign (DLFNS) has been proposed as an indirect imaging marker of high-energy pivot-shift trauma severity and has been suggested to reflect concomitant anterolateral soft-tissue injury in ACL-deficient knees. This study investigates the association between ALL injury and magnetic resonance imaging (MRI) anterolateral rotatory instability signs – including DLFNS and medial and lateral anterior tibial translation – in acute ACL injuries. 

 

A cross-sectional study was conducted on 176 patients (aged 18–50) who underwent primary ACL reconstruction. Patients were stratified by MRI-based ALL status: injured (n=40) and intact (n=136). Primary outcomes were the presence of DLFNS (depth >2 mm) and medial and lateral anterior tibial translation. Secondary outcomes included concomitant meniscal and ligamentous injuries and knee morphological characteristics. 

 

ALL injury was identified in 22.7% of patients with acute ACL rupture. DLFNS prevalence did not differ significantly between ALL-injured and intact groups (25.0% vs. 21.3%; p=0.623). No significant differences were found in medial or lateral anterior tibial translation between groups. In a subgroup of patients imaged within 30 days of injury, DLFNS was more frequent in the ALL-injured group (58.3% vs. 27.3%), but this difference did not reach statistical significance (p=0.075), likely reflecting insufficient statistical power in this subgroup. Concomitant meniscal and ligamentous injuries, and morphological parameters were comparable between groups. 

 

ALL injury was not significantly associated with MRI anterolateral rotatory instability signs. These findings suggest that DLFNS reflects the overall severity of the pivoting trauma rather than a specific marker of ALL rupture. DLFNS alone should not guide surgical decisions regarding anterolateral augmentation, requiring comprehensive clinical and imaging assessment. 

Level of evidence: Level III, cross-sectional study. 

 

Anterior cruciate ligament; Anterolateral ligament; Deep lateral femoral notch sign; Anterolateral rotatory instability; Magnetic resonance imaging; Anterior tibial translation. 

 

ACL, anterior cruciate ligament; ALC, anterolateral complex of the knee; ALL, anterolateral ligament; BMI, body mass index; DLFNS, deep lateral femoral notch sign; ICD, International Classification of Diseases; IQR, interquartile range; LCL, lateral collateral ligament; LFNS, lateral femoral notch sign; LPTS, lateral posterior tibial slope; MBA, meniscal bone angle; MCL, medial collateral ligament;