The Common Vein Copyright 2010
Definition
The anterior cruciate ligament (ACL) of the musculoskeletal system is characterized by being the weaker of the two cruciate ligaments. The cruciate ligaments crisscross within the joint caple but outside of the synovial cavity.
It is part of the knee joint. It consists of fibrous dense regular connective tissue of collagen fibers.
Its unique structural feature is that it is enveloped by a synovial membrane and surrounded by endotendineum. It is made up of multiple collagen fascicles. The ACL is about 33 mm long and 11 mm wide. The origin is the posteromedial corner of the medial part of the lateral femoral condyle in the intercondylar notch. The insertion is the on the tibia in the fossa anterior to and lateral to the spine. Some anterior fibers go on towards the transverse meniscal ligament.
There are two bundles that make up the ACL; anteromedial and posterrlateral. The anteromedial bundle is tight in flexion and the posterolateral bundle is tight in extension. The anteromedial bundle is smaller than the posterolateral bundle.
Innervation to the ACL is by the tibial nerve. The ACL has golgi tendon receptors.
The blood supply to the ACL is predominantly by the middle genicular artery. The bony attachments do not provide a significant amount of blood supply. Overall, the blood supply to the ACL is poor.
The anterior cruciate ligament as well as all other bones, muscles, and ligaments of the body are derived of mesodermal origin in the embryo.
The function of the anterior cruciate ligament is to prevent anterior tibial translation. The ultimate tensile load is 2160+/-157 N for the ACL. The stiffness of the ACL is 242+/- 28 N/mm. The posterolateral bundle of the ACL is tight in extension. The anteromedial bundle of the ACL is tight in flexion.
Common diseases include ACL tears. The ACL can be torn in combination with other ligaments or menisci in the knee. Congenital absence of the ACL can be present in conditions such as fibular hemimelia.
Commonly used diagnostic procedures include clinical history, physical exam, x-ray, and MRI.
It is usually treated with surgery or nonoperative methods depending upon what other structures are injured. Surgery is usually required for ACL injuries for highly active patients. The surgery involves replacement of the ACL with allograft tissue or autograft from the patellar tendon, quadriceps tendon, or hamstrings.
References
Elstrom J, Virkus W, Pankovich (eds), Handbook of Fractures (3rd edition), McGraw Hill, New York, NY, 2006.
Koval K, Zuckerman J (eds), Handbook of Fractures (3rd edition), Lippincott Williams & Wilkins, Philadelphia, PA, 2006.
Lieberman J (ed), AAOS Comprehensive Orthopaedic Review, American Academy of Orthopaedic Surgeons, 2008.
Moore K, Dalley A (eds), Clinically Oriented Anatomy (5th edition), Lippincott Williams & Wilkins, Philadelphia, PA, 2006.
Wheeless?s Textbook of Orthopaedics: Anatomy of the ACL (http://www.wheelessonline.com/ortho/anatomy_of_acl)