Anterior Cruciate Ligament Tears Explained

More than 600,000 people each year sustain an anterior cruciate ligament tear. It is arguably one of the most discussed topics in sports medicine. Millions of dollars have been funneled into research to find the best treatment for this injury. And every sports medicine enthusiast who follows this column knew that the subject of a torn anterior cruciate ligament was bound to come up sooner or later.

The anterior cruciate ligament (ACL) is “the big ligament” in the knee. When someone says “I tore a ligament in my knee”, odds are they are talking about the ACL. Just so that we’re all on the same page, recall that a ligament is a fibrous structure that connects one bone to another. Specifically, the ACL travels through the knee joint and attaches to the tibia in a plane anterior (in front) of its femoral origin. The primary function of the ACL is to keep the tibia form gliding forward relative to the femur. When you think about the origin and insertion of the ligament within the knee joint, this function becomes apparent.

Unfortunately, a great many people rupture the ACL every year in this country. With advancing science and technology, orthopaedic surgeons have become quite adept at dealing with the problem of a torn ACL. The “textbook” mechanism of injury for a torn ACL is “I was running, cut sharply with my foot planted, felt a pop in my knee, feel down and knew that my knee was hurt.” A myriad of variations of this history are possible. An ACL tear is not uncommon in any sport and may occur throughout a vast demographic population.

Symptoms of a torn ACL can include the following: a history similar to the one above, pain, significant swelling within the knee joint (usually due to accumulation of blood within the joint), a feeling of instability, inability to bear weight, etc. Although these are classic symptoms, findings can very markedly.

Health care providers have a variety of methods of diagnosing a torn ACL including history and mechanism of injury, a battery of manual/mechanical tests, MRI physical joint measurement. However, an experienced examiner can quite often make an accurate diagnosis using only history and physical exam.

Once the diagnosis of a torn ACL has been made, a decision regarding treatment must be considered. For the young, athletic, active patient, the decision is a no-brainer. In order for them to maintain a high level of activity, they have little choice but to have their ACL reconstructed.

ACL reconstruction can be done in a variety of ways. The most common method is to remove a portion of the patient’s own patellar tendon (the tendon that runs from the knee-cap to the tibia) and use it as a replacement for the torn ACL. A small portion of bone is preserved on either end of the tendon and it is surgically placed into the knee in the exact anatomical position of the absent ACL. The arthropscope is used to assist the surgeon in the placement of the graft. The ACL reconstruction surgery is highly successful in restoring stability and function to an injured knee. It also provides the surgeon with the opportunity to correct any other problems that he sees while reconstructing the ACL, such as a torn meniscus.

However, for the older patients or those who have a less active lifestyle, ACL reconstruction may not be the best option. In this case, many patients undergo a small arthroscopic procedure to remove any ligamentous or other debris from the knee joint and to repair a torn meniscus if one exists. Patients who do not undergo ACL reconstruction are usually fitted with a brace that will partially stabilize the injured knee when they are active.

If you have symptoms of a torn ACL, it is important that you not bear weight on the injured limb until a doctor has evaluated you. Ice and other anti-inflammatory measures are appropriate. Additionally, it is important not to delay seeking medical attention since other, less common injuries can mask themselves as a torn ACL.

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