While injury of the anterior cruciate ligament (ACL) can vary in severity, the one you’ve probably seen occurring on your TV screen or in a sports arena is an ACL tear.
To better understand what an ACL injury entails, it helps to understand the basics of the knee. Three bones join together to create the knee joint: the shinbone (tibia), the thigh bone (femur) and the kneecap (patella). The tibia and femur are connected to each other by four primary ligaments in the knee: a pair of collateral ligaments and a pair of cruciate ligaments. The collateral ligaments are found on the sides of your knee, with the lateral collateral ligament (LCL) on the outside and the medial collateral ligament (MCL) on the inside.
The cruciate ligaments cross over each other deep in the center of the knee. The ACL originates from the tibia in the front, while the posterior cruciate ligament (PCL) originates from the tibia in the back. These two ligaments then cross and attach on opposite sides of the femur in a deep central region referred to as the intercondylar notch.
By the ACL traversing from the front of the tibia up to the femur, it performs a primary function of preventing the shinbone from shifting forward. In addition to this, it gives people rotational control as well, which is why it’s so important for the function of athletes.
What Causes an ACL Injury?
Many different movements can cause ACL injuries, including many motions that are quite common when you play sports. This range includes basic movements, such as jumping and landing, suddenly changing directions or stopping, or getting hit hard on the side of the knee. Overstretching the knee joint can also lead to an ACL injury.
These are all common movements in a wide range of sports, including basketball, football and soccer. Because of that, there’s been an increased emphasis placed on ACL injury prevention in recent years, particularly among female athletes, who are at a higher risk of sustaining a torn ACL.
Symptoms of an ACL Injury
The symptoms of an ACL injury will vary somewhat depending on the severity of the injury. You might be surprised to learn that any injury to a ligament, whether a slight stretch or full tear, is referred to as a sprain. Thus, even though any ACL injury is technically a sprain—grade 3 sprains are typically referenced as complete ACL tears.
One of the most common symptoms of an ACL injury is to hear a pop emanating from the knee when cutting. When athletes talk about their injury, this popping noise is often their first indication that something is wrong with their knee.
The pop may feel like something shifted in the knee. After the pop, the outside part of the knee oftentimes will hurt because of how the knee shifts after the injury.
Other symptoms can include pain, swelling, a loss of your full range of motion, tenderness along the joint and discomfort while walking. The knee will frequently feel unstable as if it wants to buckle.
ACL Injury Treatment Options
To confirm whether you’ve experienced an ACL injury and gauge the severity of the injury, a medical provider will take a complete medical history, conduct a full examination and order imaging tests, such as X-rays and an MRI. Treatment for an ACL injury will begin with basic measures to reduce discomfort, including icing the knee, using anti-inflammatories, and a focus on regaining your knee’s range of motion.
In many cases, a torn ACL will require surgery in order to restore the stability of the knee and to prevent secondary injuries. The standard of care when undergoing surgery for an ACL tear is an ACL reconstruction. In order to reconstruct a new ACL, a graft must be fashioned either from a cadaveric donor (allograft) or from another tendon in your body (autograft). When using your own tendon, there are typically three options: your patellar tendon, quadriceps tendon or hamstring tendon.
After ACL surgery, intensive physical therapy will be needed to help restore abilities, regain range of motion, and strengthen surrounding muscles. Recovery doesn’t happen overnight, so it’s important to stick with rehabilitation until fully recovered.
In cases where someone is not a candidate for surgery due to factors like arthritis in the knee or their activity demands do not require ACL surgery, rehabilitation alone may be used to help restore knee stability and function.
ACL Injury Prevention
Because of the increase in ACL injuries over the past few decades, a good deal of research has been conducted into what causes these injuries and whether they can be prevented. While we can’t eliminate all ACL injuries, good mechanics and a training routine can help protect the knee as much as possible. While many risk factors of an ACL injury are not factors that a person can control, there are some modifiable risk factors, including safe landing mechanics and improving hamstring strength. By understanding these modifiable risk factors, ACL injury prevention training programs have been created for injury reduction.
Listen to a Podcast
Learn the science behind ACL injuries, surgical and non-surgical options, and post-op rehab. In this podcast, Dr. Michael Foster, an orthopedic surgeon at The Orthopedic Center, an affiliate of UM Shore Regional Health, and a member of the UM Joint Network, gives you a comprehensive understanding of this common knee issue.
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Medical contributions and review by Michael Foster, MD.
