The Anterior Cruciate Ligament

The Anterior Cruciate Ligament
Jessica Hess, ATC
Hughston Athletic Training Fellowship

There are oftentimes many reports of individuals within the athletic community having injured their ACL or anterior cruciate ligament. The goal of this article is to discuss what the ACL is with regards to anatomical position and its role in the human body, mechanism of injury to and rehabilitation of the anterior cruciate ligament.

What is the ACL?
The anterior cruciate ligament is one of the four major ligaments in the knee. The other three ligaments include the posterior cruciate ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL). These ligaments are the major stabilizers of the knee. The ACL is comprised of three twisted bands that prevent the femur (or large bone in thigh) moving posteriorly (backward) during weight bearing. It also stabilizes the tibia (larger bone in lower leg) against excessive internal rotation and serves as a secondary restraint to medial and lateral stress. This major stabilizing ligament often is injured during athletic participation.

ACL Injuries
The mechanism of injury to the ACL can occur in a variety of different ways. One in particular, and the most common, being a direct blow to the knee in a single-plane force. The single-plane force occurs when the lower leg is rotated while the foot is planted on the ground. An example can be when a skier skis catch snow and the body twists medial or laterally. The ACL can be injured solely or accompany other knee structures, depending on the severity of injury. It is not uncommon for someone to injure the ACL along with another ligament or knee structure

There are also different classifications of ACL injuries ranging from sprains, which are considered to be the least severe, to complete tears. The extent of injury should always be evaluated and diagnosed by a physician. During this evaluation, the use of special tests, specifically the Lachman’s and Anterior Drawer Tests, help to determine the laxity of the ligament and, in turn, the type of injury sustained to the ACL. After physical examination an MRI may be necessary to further assess the structure.

Someone that has a complete ACL tear will experience a pop followed by immediate disability and will complain that the knee feels like it is “coming apart.” An ACL tear will produce rapid swelling almost instantly within the knee. If someone has an injury of this sort they should immediately apply the RICE principle by applying rest, ice, compression and elevation. One should also contact their physician for further evaluation.

Although, a sprained ACL is usually treated by doing therapeutic exercises, a complete ACL tear, often requires surgical repair. Here the physician will transplant an external structure to replace the torn ligament. The physician may use the patients own patellar tendon or hamstring tendon to graft a new ACL. Some may also use cadaver tissue to repair the ligament. After surgery a brief hospital stay is necessary followed by a few weeks in a brace and four to six months of rehabilitation. After surgery and rehabilitation most regain full function and stability of their knee.

References:
Arnheim, D.D., Prentice, W. E. Principles of Athletic Training. 10th ed.
Starkey, C., Ryan, J. Evaluation of Orthopedic and Athletic Injuries. 2nd ed.


Jessica Hess, ATC, is a second year graduate student and recipient of the Hughston Athletic Training Fellowship in Columbus, Georgia. She earned a bachelors degree in Health Management with an emphasis in Athletic Training from Southeast Missouri State University, Cape Girardeau, Missouri.

While at SEMO, she received the Athletic Training Major of the Year award, an honor given by the College of Health and Human Performance.

She is an active member of the National Athletic Trainer’s Association (NATA) and currently serves as the Head Athletic Trainer at Spencer High School, Columbus, Georgia.

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