ACL Injury: Discover the Causes, Symptoms, and Effective Treatments

What is Anterior cruciate ligament injury (ACL)?

The knee is a hinge joint which is held together by four ligaments. There are two ligaments on each side of the knee, called collateral ligaments. The other two ligaments are found deeper in the knee joint, which cross each other and are called cruciate ligaments. [1] These cruciate ligaments are known as anterior and posterior cruciate ligaments, depending on their location. These ligaments are attached to the thigh bone (femur) on one side and the shinbone (tibia) on the other. [2]

Injury to these ligaments due to any cause, like trauma or surgery, can lead to the instability of the knee joint. Among the two cruciate ligaments, anterior cruciate ligament (ACL) injury is the most common. Most of these ACL injuries occur in athletes, especially during sports requiring sudden stopping or direction changes. It can also occur due to a direct strike to the knee from player-to-player contact, sometimes caused by sudden jumping or landing. [3] Sports likely to cause ACL injury include soccer, basketball, football, and gymnastics. ACL injuries are, however, also seen in cases of work injuries or road traffic accidents. [4]

Risk Factors of ACL Injury

Numerous factors may increase your risk of an ACL injury. The common risk factors are:

• Female: ACL injuries are found to be more common among females. This could be due to the anatomical differences in the knee joint or the effect of hormones on bones.[5]
• Athlete: Since ACL injuries occur during various sports activities, athletes are always at increased risk of this injury.
• Higher BMI: Increased BMI has been found to have a two times higher risk of causing ACL injury than among those who are not obese.[6,7]
• Knee Alignment: If your knee is positioned inward, it can increase the stress on the anterior cruciate ligament during movement, increasing your risk of injury.
• Overtraining: Inadequate rest and excessive repeated moments with the knee can strain the ligaments, increasing the risk of injury.

Symptoms of ACL Injury

The symptoms can vary in intensity depending on the severity of the injury. Some of the common signs are:

1. Popping Sensation

Many people report hearing or feeling a pop at the moment the ACL is injured. The sound is often an indicator of a complete tear of the ligament.

2. Severe Pain

You may have severe and immediate pain after the injury. It can be intense and prevent you from continuing the activity, such as walking or running.

3. Rapid Swelling

Swelling due to an ACL injury develops within a few hours of the injury due to bleeding within the joint. Sometimes, swelling may appear almost immediately or within the first 24 hours.

4. Giving Away

Your knee might feel unstable or as though it could buckle, especially when trying to turn or put some weight on it while walking.

5. Decreased Range of Motion

After an ACL injury, you might feel stiffness or restricted ability to bend or straighten your knee fully. [8]

Diagnosis of ACL Injury

The ACL injury can be diagnosed by a history, physical examination, and imaging test.

1. Provocative Maneuvers

Your doctor might see the changes during the provocative maneuvers to help diagnose. During Lachman test, the ACL will allow the tibial bone to move forward more than normal, indicating ligament instability. With your knee bent at 90°, the tibia will have an excessive forward moment hinting towards a torn ACL during the anterior drawer test. The pivot shift test, done to assess the knee’s stability, will show shifting of the tibia during the rotation and flexion of the knee joint, indicating an ACL injury.

2. X-rays

Although X-rays cannot damage, they are often done to rule out fractures or other bone injuries that may have occurred during the incident.

3. Magnetic Resonance Imaging (MRI)

MRI is the most accurate imaging test for diagnosing ACL injuries. The test is 97.4% sensitive, with an accuracy of 92%. An MRI can show the extent of the ligament and any associated injuries, such as damage to the meniscus cartilage or other ligaments. [9,10]

4. Functional Ultrasound (USG)

In resource-limited situations where an ACL injury is suspected, functional USG can be used as the first investigative technique. It has a good sensitivity (81.65%) and specificity (89%) for detecting ACL injury.[11]

5. Knee Arthroscopy

A knee arthroscopy may be performed in cases where the diagnosis remains unclear after the clinical and imaging evaluation. This is a minimally invasive procedure where a tiny camera is inserted into the knee to visualize the injury directly. Sometimes, this can be used even to manage the case. 12]

Treatment for ACL Injury

Treatment of ACL injuries depends on the severity of the injury, your activity level, and long-term goals.

Non-Surgical Treatment Of ACL Injury

Non-surgical treatment is more suitable for less severe injuries.

• First Aid: General care and first aid measures may be enough for minor injuries. Regular application of ice packs may help with swelling. Further, compression bandage also reduces swelling. Elevating your leg, staying off your feet, and using crutches are other first-aid measures.
• Medications: Pain medications are the primary way to manage the condition. Your doctor might prescribe you non-steroid anti-inflammatory drugs or may even provide you with steroids to reduce the inflammation in the joint.
• Physiotherapy: Physiotherapy is an essential component of the treatment as it helps improve knee strength, stability, and range of motion. Exercises that target strengthening the muscles around the knee, improving balance, and stretching can help restore the full range of motion.

Surgical Treatment Of ACL Injury

Anterior cruciate ligament reconstruction(ACLR) is the surgical technique often done where the ligament is reconstructed using a graft taken from your body or tissue from a donor. [13]

ACL Reconstruction Surgery

ACL reconstruction surgery is a procedure used to fix a torn anterior ligament. Reconstruction is like replacing a broken rope in your knee with a new one, strengthening and stabilizing your knee. The surgery is usually recommended if the ACL is completely torn, your knee feels unstable, making it hard to do sports, or you want to return to high-demand sports and physical activity that requires knee stability.

During reconstruction, the surgeon makes a small cut around your knee, and a tiny camera called an arthroscope is inserted to see what is inside your knee. The torn ACL is then located and removed. The new replacement ligament harvested from yourself or the donor is placed where the old ligament was present. The surgery usually takes about 1 to 2 hours, and most patients can go home the same day. Arthroscopic reconstruction is more commonly used than open-knee surgery. [14 ]

Recovering from a reconstruction surgery is another essential part of the treatment. You need to rest your knees and use only crutches for a few weeks before you can start walking. You also need to coordinate with your physical therapist to regain your knees’ strength, flexibility, and balance. For most people, returning to sports or intense physical activity takes around 6 to 9 months. [15,16]

As with many other surgical procedures, ACLR can cause a number of potential complications, including infection, blood clots or hemorrhage at the site, stiffness and knee discomfort, and graft failure or poor healing.

Reoccurrence of ACL injury

Even after successful treatment or surgery, injuries can re-occur. Studies show that about one in five people experience re-injury. [17]  The risk of tearing the ACL in the opposite knee is also higher in people with an injury. [17]

Returning to sports too soon, especially high-demand sports like soccer, basketball, or skiing, before the knee fully recovers increases the risk of re-injury. Poor rehabilitation or not completing a full rehabilitation program can leave the knee unstable, leading to a higher chance of re-injury.

With proper rehabilitation, strength training, and a gradual return to activities, you can resume sports without reinjury.

Five tips to prevent ACL injuries

1. Wear proper protective gear and equipment.
2. Stretch and warm up before sports.
3. Wear shoes that fit you right.
4. Rest and stretch after sports activities.
5. Don’t ignore symptoms like pain and swelling.

Questions to ask your Doctor

1. Should I get surgery for my ACL injuries?
2. When will I be able to return to playing sports again?
3. Can I have an ACL tear again in the future?
4. How do I know if my ACL is completely recovered?
5. How can I prevent reinjury after I recover?

References

1. In brief: What are ligaments? 2018.Institute for Quality and Efficiency in Health Care (IQWiG); 2006-. In brief: What are ligaments? 2018 Jul 26. Available from: https://www.ncbi.nlm.nih.gov/books/NBK525790/
2. Gupton M, Imonugo O, Black AC, Launico M V., Terreberry RR. Anatomy, Bony Pelvis and Lower Limb, Knee. StatPearls 2023.
3. Alsubaie SF, Abdelbasset WK, Alkathiry AA, Alshehri WM, Azyabi MM, Alanazi BB, et al. Anterior cruciate ligament injury patterns and their relationship to fatigue and physical fitness levels – a cross-sectional study. Medicine 2021;100. https://doi.org/10.1097/MD.0000000000024171.
4. LaBella CR, Hennrikus W, Hewett TE, Brenner JS, Brooks A, Demorest RA, et al. Anterior Cruciate Ligament Injuries: Diagnosis, Treatment, and Prevention. Pediatrics 2014;133:e1437–50. https://doi.org/10.1542/PEDS.2014-0623.
5. Alsubaie SF, Abdelbasset WK, Alkathiry AA, Alshehri WM, Azyabi MM, Alanazi BB, et al. Anterior cruciate ligament injury patterns and their relationship to fatigue and physical fitness levels – a cross-sectional study. Medicine 2021;100. https://doi.org/10.1097/MD.0000000000024171.
6. Weir CB, Jan A. BMI Classification Percentile And Cut Off Points. StatPearls 2019.
7. Alsayed HN, Alkhateeb MA, Aldossary AA, Houbani KM, Aljamaan YM, Alrashidi YA. Risk of anterior cruciate ligament injury in population with elevated body mass index. Med Glas (Zenica) 2023;20:83–7. https://doi.org/10.17392/1517-22.
8. Sokal PA, Norris R, Maddox TW, Oldershaw RA. The diagnostic accuracy of clinical tests for anterior cruciate ligament tears are comparable but the Lachman test has been previously overestimated: a systematic review and meta-analysis. Knee Surgery, Sports Traumatology, Arthroscopy 2022;30:3287. https://doi.org/10.1007/S00167-022-06898-4.
9. Lukas S, Putman S, Delay C, Blairon A, Chazard E, Letartre R. Knee Ligament Sprains: Diagnosing Anterior Cruciate Ligament Injuries by Patient Interview. Development and Evaluation of the Anterior Cruciate Ligament Injury Score (ACLIS). Orthopaedics and Traumatology: Surgery and Research 2022;108. https://doi.org/10.1016/j.otsr.2022.103257.
10. D’Ambrosi R, Di Maria F, Ursino C, Ursino N, Di Feo F, Formica M, et al. Magnetic resonance imaging shows low sensitivity but good specificity in detecting ramp lesions in children and adolescents with ACL injury: A systematic review. Journal of ISAKOS 2024;9:371–7. https://doi.org/10.1016/j.jisako.2023.12.005.
11. Kumar S, Kumar A, Kumar S, Kumar P. Functional Ultrasonography in Diagnosing Anterior Cruciate Ligament Injury as Compared to Magnetic Resonance Imaging. Indian J Orthop 2018;52:638. https://doi.org/10.4103/ORTHO.IJORTHO_28_17.
12. Laprade RF, Spalding T, Murray IR, Chahla J, Safran MR, Larson CM, et al. Knee arthroscopy: evidence for a targeted approach. Br J Sports Med 2021;55:707. https://doi.org/10.1136/BJSPORTS-2020-103742.
13. Knee ligament surgery – NHS n.d. https://www.nhs.uk/conditions/knee-ligament-surgery/
14. Macaulay AA, Perfetti DC, Levine WN. Anterior Cruciate Ligament Graft Choices. Sports Health 2012;4:63. https://doi.org/10.1177/1941738111409890.
15. Brukner P, Clarsen B, Cook J, Cools A, Crossley K, Hutchinson M, et al. Brunkner & Khans’s Clinical Sports Medicine: Injuries. Brunkner & Khans’s Clinical Sports Medicine: Injuries 2017:287.
16. Eitzen I, Holm I, Risberg MA. Preoperative quadriceps strength is a significant predictor of knee function two years after anterior cruciate ligament reconstruction. Br J Sports Med 2009;43:371–6. https://doi.org/10.1136/BJSM.2008.057059.
17. Rigg JD, Panagodage Perera NK, Toohey LA, Cooke J, Hughes D. Anterior cruciate ligament injury occurrence, return to sport and subsequent injury in the Australian High Performance Sports System: A 5-year retrospective analysis. Physical Therapy in Sport 2023;64:140–6. https://doi.org/10.1016/J.PTSP.2023.10.001.