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.
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ACL injury is caused by 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't heal by itself, but surgery may not be needed if the knee is stable. This option may be best in those who are elderly or less active. Those who are highly active or want 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 who are young and active or those who want to return to intense sports. It may also be needed if other ligaments of the knee are damaged or the knee is 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 sports.
The physical therapist can test your knee movement and develop a recovery plan. Therapy can include exercise and stretching programs to help balance the muscles of your legs. This can help stabilize the knee and decrease the risk of further injury.
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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7/6/2009 DynaMed Plus Systematic Literature Surveillancehttp://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 Surveillancehttp://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 2018 by EBSCO Medical Review Board Teresa Briedwell, PT, DPT Last Updated: 3/15/2017