An injury to the Anterior Cruciate Ligament can be a debilitating musculoskeletal injury to the knee, seen most often in athletes. Non-contact tears and ruptures are the most common causes of ACL injury.

The anterior cruciate ligament (ACL) is an important ligament for proper movement. ACL injury more commonly causes knee instability than does injury to other knee ligaments. Injuries of the ACL range from mild such as small tears to severe when the ligament is completely torn. There are many ways the ACL can be torn; the most prevalent is when the knee is bent too much toward the back and when it goes too far to the side. Tears in the anterior cruciate ligament often take place when the knee receives a direct impact from the front of the thigh while the leg is in a stable position. Torn ACL’s are most often related to high impact sports or when the knee is forced to make sharp changes in movement and during abrupt stops from high speed. These types of injuries are prevalent in Alpine skiing, Research has shown that women involved in sports are more likely to have ACL injuries than men. Indeed, women are 5 times more likely to suffer from ACL injuries in general. ACL tears can also happen in older individuals through slips and falls and are seen mostly in people over forty due to wear and tear of the ligaments. An ACL tear can be determined by an individual if a popping sound is heard after impact, swelling after a couple of hours, severe pain when bending the knee, and when the knee buckles or locks during movement or gives way while standing still with weight on the affected knee.

Signs and Symptoms

Symptoms of an ACL injury include hearing a sudden popping sound, swelling, and instability of the knee (i.e., a "wobbly" feeling). Pain is also a major symptom in an ACL injury and can range from moderate to severe. Continued athletic activity on a knee with an ACL injury can have devastating consequences, resulting in massive cartilidge damage, leading to an increased risk of developing osteoarthritis later in life. 

Causes

ACL injuries occur when an athlete rapidly decelerates, followed by a sharp or sudden change in direction (cutting). ACL failure has been linked to heavy or stiff-legged landing; as well as twisting or turning the knee while landing, especially when the knee is in the valgus (knock-knee) position.

The majority of ACL injuries occur in athletes landing flat on their heels. The latter directs the forces directly up the tibia into the knee, while the straight-knee position places the lateral femoral condyle on the back-slanted portion of the tibia. The resultant forward slide of the tibia relative to the femur is restrained primarily by the now-vulnerable ACL.

Treatment

The ACL primarily serves to stabilize the knee in an extended position and when surrounding muscles are relaxed; so if the muscles are strong, many people can function without it. Fluids will also build the muscle.

The term for non-surgical treatment for ACL rupture is "conservative management", and it often includes physical therapy and using a knee brace. Lack of an ACL increases the risk of other knee injuries such as a torn meniscus, so sports with cutting and twisting motions are strongly discouraged. For patients who frequently participate in such sports, surgery is often indicated.

Patients who have suffered an ACL injury should always be evaluated for other knee injuries that often occur in combination with an ACL tear. These include cartilage/meniscus injuries, bone bruises, PCL tears, posterolateral injurues and collateral ligament injuries.

Prevention

Research has shown that the incidence of non-contact ACL injury can be reduced anywhere from 20% to 80% by engaging in regular neuromuscular training that is designed to enhance proprioception, balance, proper movement patterns and muscle strength.[12]

References

1. ^ Levy DB, Dickey-White HI. Knee Injury, Soft Tissue, eMedicine, Dec 15, 2009
2. ^ Dr Langran. "Alpine Ski Injuries". Ski-Injury.com. http://www.ski-injury.com/specific-sports/alpine. Retrieved 5 December 2010.
3. ^ Wilson, Chloe. "ACL knee injuries". Knee Pain Explained.com. http://www.knee-pain-explained.com/ACL-knee-injuries.html. Retrieved 27 December 2011.
4. ^ http://www.sports-injury-info.com/symptoms-of-a-torn-acl.html
5. ^ Catalyst: Weak at the Knees - ABC TV Science
6. ^ McLean SG, Huang X, van den Bogert AJ (2005). "Association between lower extremity posture at contact and peak knee valgus moment during sidestepping: implications for ACL injury". Clin Biomech (Bristol, Avon) 20 (8): 863–70. doi:10.1016/j.clinbiomech.2005.05.007. PMID 16005555. http://linkinghub.elsevier.com/retrieve/pii/S0268-0033(05)00111-7.
7. ^ A Genetic Link for ACL Injuries, Science of Soccer Online
8. ^ "Anterior Drawer Test - Wheeless' Textbook of Orthopaedics". http://www.wheelessonline.com/ortho/anterior_drawer_test.
9. ^ "Lachman Test - Wheeless' Textbook of Orthopaedics". http://www.wheelessonline.com/ortho/lachman_test.
10. ^ Starkey's Evaluation of Orthopedic and Athletic Injuries
11. ^ http://johnlachmansociety.org/
12. ^ Patrick, Dick (2003-06-24). "Specific exercises may be key to preventing ACL injuries". USA Today. http://www.usatoday.com/sports/2003-06-24-acl-cover_x.htm.
13. ^ Cluett, Jonathan. "ACL Reconstruction." About.com. The New York Times Company, 07 Sept 2010. Web. 7 Dec 2010. <http://orthopedics.about.com/cs/aclrepain/a/aclgrafts.htm
14. ^ Mohtadi, NG; Chan, DS, Dainty, KN, Whelan, DB (2011 Sep 7). "Patellar tendon versus hamstring tendon autograft for anterior cruciate ligament rupture in adults.". Cochrane database of systematic reviews (Online) 9: CD005960. PMID 21901700.
15. ^ http://www.ehealthmd.com/library/acltears/ACL_rehab.html
16. ^ Mountcastle, Sally; et al. "Gender Differences in Anterior Cruciate Ligament Injury Vary With Activity. The American Journal of Sports Medicine. 35.10 (2007)".