Anterolateral Ligament of the Knee Shows Variable Anatomy in Pediatric Specimens.

Background: Anterior cruciate ligament (ACL) reconstruction failure rates are highest in youth athletes. The role of the anterolateral ligament in rotational knee stability is of increasing interest, and several centers are exploring combined ACL and anterolateral ligament reconstruction for these young patients. Literature on the anterolateral ligament of the knee is sparse in regard to the pediatric population. A single study on specimens younger than age 5 years demonstrated the presence of the anterolateral ligament in only one of eight specimens; therefore, much about the prevalence and anatomy of the anterolateral ligament in pediatric specimens remains unknown.

Questions/purposes: We sought to (1) investigate the presence or absence of the anterolateral ligament in prepubescent anatomic specimens; (2) describe the anatomic relationship of the anterolateral ligament to the lateral collateral ligament; and (3) describe the anatomic relationship between the anterolateral ligament and the physis.

Methods: Fourteen skeletally immature knee specimens (median age, 8 years; range, 7-11 years) were dissected (12 male, two female specimens). The posterolateral structures were identified in all specimens, including the lateral collateral ligament and popliteus tendon. The presence or absence of the anterolateral ligament was documented in each specimen, along with origin, insertion, and dimensions, when applicable. The relationship of the anterolateral ligament origin to the lateral collateral ligament origin was recorded.

Results: The anterolateral ligament was identified in nine of 14 specimens. The tibial attachment point was consistently located in the same region on the proximal tibia, between the fibular head and Gerdy's tubercle; however, the femoral origin of the anterolateral ligament showed considerable variation with respect to the lateral collateral ligament origin. The median femoral origin of the anterolateral ligament was 10 mm (first interquartile 6 mm, third interquartile 13) distal to the distal femoral physis, whereas its median insertion was 9 mm (first interquartile 5 mm, third interquartile 11 mm) proximal to the proximal tibial physis.

Conclusions: The frequency of the anterolateral ligament in pediatric specimens we observed was much lower than other studies on adult specimens; future studies might further investigate the prevalence, development, and functional role of the anterolateral ligament of the knee.

Clinical Relevance: This study expands our understanding of the anterolateral ligament and provides important anatomic information to surgeons considering anterolateral ligament reconstruction concomitantly with primary or revision ACL reconstruction in pediatric athletes.