Anterior Cruciate Ligament (ACL)

Introduction

The anterior cruciate ligament (ACL) is a band of dense connective tissue which courses from the femur to the tibia. The ACL is a key structure in the knee joint, as it resists anterior tibial translation and rotational loads.

Attachments

Origin

Arises from the posteromedial corner of medial aspect of lateral femoral condyle in the intercondylar notch.  This femoral attachment of ACL is on posterior part of medial surface of lateral condyle well posterior to longitudinal axis of the
femoral shaft.  The attachment is actually an interdigitation of collagen fibers & rigid bone thru transitional zone of
fibrocartilage and mineralized fibrocartilage.

Insertion

Anterior to the intercondyloid eminence of the tibia, being blended with the anterior horn of the medial meniscus.  The tibial attachment is in a fossa in front of & lateral to anterior spine, a rather wide area from 11 mm in width to 17 mm in AP direction

Nerve Supply

The ACL is innervated by posterior articular branches of the tibial nerve.

Vascular Supply

The ACL is vascularized by branches of the middle genicular artery.

Features

The ACL has a microstructure of collagen bundles of multiple types (mostly type I) and a matrix made of a network of proteins, glycoproteins, elastic systems, and glycosaminoglycans with multiple functional interactions. There are two components of the ACL, the anteromedial bundle (AMB) and the posterolateral bundle (PLB), named according to where the bundles insert into the tibial plateau. They are not isometric with the main change being lengthening of the AMB and shortening of the PLB during flexion.

Function

Resists anterior translation and medial rotation of the tibia, in relation to the femur.