An anterior cruciate ligament (ACL) injury is a tear in a ligament of the knee. The ACL is a tough band of fiber in the middle of the knee joint. It connects the lower leg bone to the thigh bone. The ACL keeps the knee stable during movement by keeping the lower leg bone from sliding too far forward. An injury to this ligament can make the knee unstable. The injury may be partly torn or a complete tear.
ACL injury is caused be excess force on the knee. It occurs most often when your knee gets twisted or during a hard landing from a jump. It can also happen with:
Factors that increase your chance of ACL injury include:
Symptoms may include:
You will be asked about your symptoms and how you injured your knee. A physical exam will be done and your doctor will test your knee's strength and stability.
The doctor may do further tests to see if there is any other damage to the joint. This may be done with:
Ligament sprains are graded according to their severity:
Talk with your doctor about the best treatment plan for you. Recovery time will depend on the severity of the injury. Immediate care includes:
The ACL can not heal by itself but if the knee is fairly stable surgery may not be needed. This option may be best in those that are less active or elderly. Those that are highly active or wish to return to sports will probably need surgery.
A knee brace can help keep the knee stable. Crutches may also be helpful in the beginning.
Over-the-counter or prescription medications may be used to reduce pain and swelling.
Surgery may be needed for those that are young and active or those that need to return to intense sports. It may also be needed if other ligaments of the knee are damaged or the knee is very unstable.
The surgery will use tissue from another part of the body to make a new ligament. It can take several months for the graft to become strong enough to return to sport activity.
To reduce your chance of injuring the ACL:
OrthoInfo—American Academy of Orthopaedic Surgeons
Sports Med—American Orthopaedic Society for Sports Medicine
Canadian Orthopaedic Association
Canadian Orthopaedic Foundation
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Anterior cruciate ligament injuries. Ortho Info—American Academy of Orthopaedic Surgeons website. Available at: http://orthoinfo.aaos.org/topic.cfm?topic=A00549. Updated March 2014. Accessed February 29, 2016.
Anterior cruciate ligament injuries: treatment and rehabilitation. Encyclopedia of Sports Medicine and Science website. Available at: http://sportsci.org/encyc/aclinj/aclinj.html. Updated April 18, 1998. Accessed February 29, 2016.
ACL Injury: Does It Require Surgery? American Academy of Orthopaedic Surgeons website. Available at: http://orthoinfo.aaos.org/topic.cfm?topic=A00297. Updated September 2009. Accessed February 29, 2016.
Griffin LY, Agel J, et al. Noncontact anterior cruciate ligament injuries: risk factors and prevention strategies. J Am Acad Orthop Surg. 2000;8:141-150.
Knee sprains and meniscal injuries. Merck Manual for Health Care Professionals. Available at: http://www.merckmanuals.com/professional/injuries_poisoning/fractures_dislocations_and_sprains/knee_sprains_and_meniscal_injuries.html. Updated December 2014. Accessed February 29, 2016.
Ligament injuries to the knee. John Hopkins Medicine website. Available at. http://www.hopkinsmedicine.org/healthlibrary/conditions/adult/orthopaedic_disorders/ligament_injuries_to_the_knee_85,P00926. Accessed February 29, 2016.
7/6/2009 DynaMed Plus Systematic Literature Surveillance http://www.dynamed.com/topics/dmp~AN~T114675/Anterior-cruciate-ligament-ACL-injury: Prodromos CC, Han Y, et al. A meta-analysis of the incidence of anterior cruciate ligament tears as a function of gender, sport, and a knee injury-reduction regimen. Arthroscopy. 2007;23:1320-1325.
5/12/2014 DynaMed Plus Systematic Literature Surveillance http://www.dynamed.com/topics/dmp~AN~T114675/Anterior-cruciate-ligament-ACL-injury: Anterior cruciate ligament injuries: Diagnosis, treatment, and prevention. Pediatrics. 2014 Apr [Epub ahead of print].
Last reviewed March 2017 by EBSCO Medical Review BoardTeresa Briedwell, PT, DPT
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.