Anterior Cruciate Ligament (ACL) Injury

Ligaments are strong bands of tissue that connect bones in the body. The anterior cruciate ligament (ACL) is one of four key ligaments in the knee, and one of the two ligaments that cross in the middle of the knee, connecting the femur (thigh bone) to the tibia (shin bone), helping to stabilize the knee joint (Mayo Clinic Staff, 2022). ACL injuries are one of the most common knee problems, especially among athletes. This ligament plays a crucial role in stabilizing the knee, and injuries can occur from sudden movements, such as cutting, jumping, or contact with an opponent. While most often occurring in sports like football, basketball, and tennis, ACL injuries can also happen during everyday activities. Depending on the severity of the injury, treatment may be conservative or require surgery. This article provides an overview of the symptoms, causes, diagnosis, and treatment options for ACL injuries, as well as the importance of proper recovery.

Risk Factors and Causes of Injury

ACL injuries are common in sports that put pressure on the knee and require sudden changes of direction, such as football, basketball, and lacrosse. The majority of injuries occur during activities involving rapid twisting or cutting movements, but they can also happen in everyday movement. These injuries are most often unintentionally caused when a person’s foot “catches” on the ground, and the leg is overextended with force directed outward. Interestingly, women are more likely to experience this type of injury than men (Walker et al, 2015). In addition, common risk factors for ACL injury include poor physical conditioning, using improper movement patterns (such as allowing the knees to move inward during squats), wearing ill-fitting footwear, using poorly maintained sports equipment (such as improperly adjusted ski bindings), and playing on artificial turf (Mayo Clinic Staff, 2022).

Common causes of ACL injury include:

• Sudden deceleration and change of direction (cutting)
• Twisting while the foot is firmly planted on the ground
• Improper landing after a jump
• Sudden stopping
• Direct impact or collision, as seen in American football (Mayo Clinic Staff, 2022).

Symptoms of Injury

• A “popping” sound in the knee – Many people hear a popping sound in their knee when an injury occurs, although not everyone experiences this.
• Pain – If the injury is minor, there may be little pain. However, discomfort may be felt along the knee joint line. Some individuals have difficulty standing or putting pressure on the injured leg.
• Swelling – Swelling typically occurs within the first 24 hours and can be reduced by applying ice to the knee and elevating the injured leg on a pillow.
• Difficulty walking – If you can place weight on the injured leg, you may notice it is harder to walk than usual. Some people feel that their knee joint is less stable.
• Decreased range of motion – After ACL damage, it is very likely that you won’t be able to bend or straighten your knee as you did before the injury (Powell, 2024).

Some individuals feel intense pain right away, while others may be able to walk for a few hours after the injury. However, as time passes and the swelling in the knee increases, it becomes more difficult to move, and the range of motion decreases (UPMC, n.d.).

Diagnosis of ACL Injury

When the ligament is damaged, it usually results in a partial or complete tear of the tissue. A mild injury may stretch the ligament but leave it intact (Mayo Clinic Staff, 2022). If you suspect you’ve injured your ACL, it is important to see a doctor as soon as possible, as the best time to diagnose the injury is within the first hour after it happens, before significant swelling occurs. Quick action can help accurately determine the severity of the injury and begin appropriate treatment (UPMC, n.d.). A doctor may perform several tests to make a precise diagnosis:

• Tests – The doctor will ask you to lie on your back and bend your hips and/or knees at certain angles. Then, they will place their hands on various parts of your leg and gently move it. If any bone moves abnormally, it may indicate that the ACL is injured.
• X-ray – While X-rays cannot show soft tissues like the ACL, the doctor may order one to rule out bone fractures.
• MRI or ultrasound – These scans can show both bones and soft tissues. If your ACL is damaged, the injury will appear on the images.
• Arthroscopy – This procedure involves the doctor “looking inside the joint.” The surgeon makes a small incision in the skin, then inserts a small camera that displays the joint image on a screen. This exam helps the doctor see the exact type of injury and, if necessary, immediately correct or repair it (Powell, 2024).

Treatment of ACL Injury

The goal of treating an anterior cruciate ligament injury is to stabilize the knee and restore normal range of motion. To decide the best course of treatment, the doctor will consider several factors, such as the patient’s age, activity level, and the extent of the ACL injury.

For minor ACL injuries, treatment often does not require surgery. In these cases, the doctor may recommend wearing a protective brace, resting, and engaging in physical therapy. Some tips for treating a minor injury include:

• Applying ice to the injured knee several times a day to reduce swelling
• Elevating the knee above heart level to decrease swelling
• Compressing the knee with a bandage or elastic wrap
• Doing exercises to strengthen muscles to aid recovery
• Taking time off from activities for several weeks
• Using anti-inflammatory and pain-relieving medications to reduce swelling and speed recovery (UPMC, n.d.).

However, if the injury is severe and there is a complete ACL tear, surgery is necessary. ACL injuries typically do not heal on their own, and without surgery, the knee can become unstable, increasing the risk of further injuries in the future. Surgical treatment includes two main types of operations:

• ACL Repair – The surgeon attempts to repair the original ligament, encouraging its natural healing.
• ACL Reconstruction – If the ligament cannot be repaired, tissue from the patient’s body (or a donor) is used to reconstruct a new ligament.

After surgery, recovery time and physical rehabilitation are required to restore knee stability and allow a return to normal activities, including sports (UPMC, n.d.). Returning to a previous activity level may take one year or more. During rehabilitation, your doctor and physical therapist will test the stability and strength of your knee and assess its functionality. Research shows that up to one-third of athletes with ACL injuries will suffer another tear within two years. You can reduce the chances of re-injury by allowing more time for recovery (Powell, 2024).

Conclusion

Injuries to the anterior cruciate ligament can significantly impact the ability to perform everyday activities and athletic endeavors. Prompt diagnosis and timely treatment are crucial for effective recovery. While minor injuries may be treated without surgery, more severe injuries require surgical intervention that can provide long-term knee stability. It is essential that the injured knee joint undergoes careful rehabilitation, as a lack of proper recovery can increase the risk of reinjury.

*This text is for informational purposes only. If any symptoms occur, it is recommended to seek advice from a doctor or qualified healthcare professional.

References

• Walker, G.N., D’Auria, J., Cui, L.R., Van Eck, C.F., & Fu, F.H. (2015). Anatomic anterior cruciate ligament reconstruction. Medicina Fluminensis, 51(1), 27-40. Retrieved from: https://hrcak.srce.hr/135675
• Singh, Y. (2020, May 17). 2 men in red and white jersey shirt sitting on grass field [Photograph]. Unsplash. https://unsplash.com/photos/2-men-in-red-and-white-jersey-shirt-sitting-on-ground-during-daytime-KtPJkTlke8Y
• Mayo Clinic Staff. (2022, December 1). ACL injury symptoms and causes. Mayo Clinic. Retrieved March 12, 2025, from https://www.mayoclinic.org/diseases-conditions/acl-injury/symptoms-causes/syc-20350738#:~:text=An%20ACL%20injury%20is%20a,to%20your%20shinbone%20(tibia).
• Powell, A. (2024, January 16). Anterior cruciate ligament (ACL) injury and treatment. WebMD. https://www.webmd.com/pain-management/knee-pain/acl-injury-what-to-know
• UPMC. (n.d.). ACL injury. UPMC. Retrieved March 12, 2025, from https://www.upmc.com/services/orthopaedics/conditions/acl-injury