The anterior cruciate ligament (ACL) is one of the major ligaments in the knee. It is located in the center of the knee, with attachments on the lateral aspect of the femoral notch of the lateral femoral condyle and inserts just in front of the intercondylar eminence on the tibia. It’s main function is preventing the tibia (shin bone) from translating anteriorly (to the front). It also helps with internal rotational stability of the tibia. Overall, the ACL provides roughly 85% over the overall stability to the knee.
The ACL is the most commonly injured ligament of the knee. Approximately 70% of all ACL injuries occur from non-contact activities with most of these occurring in athletes performing a sudden deceleration, landing or pivoting movement. A high risk position of the knee during these events tends to occur when the knee is in a valgus position (knock knee) and in slight flexion. This position tends to occur more commonly in females.
When an ACL rupture occurs, the patient will often recall a “pop” followed by swelling and a sensation of instability. When the initial pain and swelling occurs, the patient may complain of the knee “giving out” predominantly when most of the body weight is on the injured knee such as negotiating stairs, squatting, or pivoting/changing directions. Often times when an ACL injury occurs, there can be associated injuries to the meniscus and lateral tibial plateau.
If your provider suspects an ACL injury after examination, they will order an xray and likely an MRI to further evaluate the knee. The xray is ordered to assess any bony injury that may have occurred. The MRI will give a more detailed assessment and understanding of the injury to the bone and soft tissues of the knee.
Treatment of an acute ACL tear varies depending on patient activity, life demands and perceived laxity to name a few. Concomitant injuries can also play a role in determining if surgery is required. In a relatively inactive older patient who does not require high demands on the knee and if there is no perceived instability, then ACL surgery may not be required. However, in younger patients, there is perceived instability of the knee or those who are quite active, ACL reconstruction is recommended. ACL reconstruction is generally an outpatient procedure.
Once reconstruction is chosen, your surgeon will discuss various methods and graft types to reconstruction the ACL. Graft options include autograft (taken from the patient) and allograft (taken from a cadaver). In a younger patient, autograft is often selected and in an older patient allograft is most likely to be chosen. Your surgical team can discuss options with you.
Surgery is the only option to be able to repair the ligament completely but there are different grafts that you can choose from and depending on your age, there might be a better graft to choose. There is the patellar graft from your own patela tendon, there is your own hamstring tendon to choose from or you can also get an ACL graft from a cadaver.
Below is a link to view how the ACL is grafted and fit to the knee
