There are four knee ligaments that play a role in the proper function of the knee. One ligament is the anterior cruciate ligament (ACL) which stabilizes the knee and helps it move in the correct direction. If enough force is placed on the ligament, it can stretch and tear. The ACL is the most commonly injured of the four knee ligaments.
Causes
An ACL tear can occur when the ligament becomes stressed beyond its normal range usually due to an injury. For example, an ACL injury may be the result of the knee becoming over straightened from a contact injury. Having the knee hit from the side can also tear the ligament. People who participate in certain contact sports, such as basketball and football are at a higher risk of tearing their ACL.
Symptoms and Natural History
As soon as the injury occurs, a popping sound in the knee may be heard. There will also be immediate pain in the knee. Swelling may occur within an hour as fluid starts to accumulate in the knee joint. Swelling may continue to get worse for several hours after the injury. The knee may also feel unstable.
The extent of the tear may play a role in the severity of symptoms. Slight tears may not cause a great deal of pain. But in other cases, an ACL tear can prevent participation in recreational activities including sports. Walking may also be difficult until the tear heals.
Diagnosis
In order to diagnose an ACL tear, a review of the injury along with a physical exam of the knee is performed. The knee will be assessed for tenderness and swelling. Different techniques may also be done to test the stability of the knee. An MRI is often the preferred imaging technique used to diagnose injuries to the ligament.
Self-help Treatments for an ACL Tear
Immediate first aid for an ACL tear involves applying ice to the knee to reduce swelling and pain. Elevating the knee may also help reduce swelling. Wearing a knee brace may be advised to provide stability for the knee.
Standard Clinical Treatments for an ACL Tear
Medication can be used to treat the pain associated with an ACL tear, but it will not heal the tear. Depending on the severity of the tear and the activity level of the person, additional clinical treatments may be needed including surgery.
In people who are less active and often older, non-surgical treatments may be adequate. For example, after the swelling has decreased, physical therapy may help improve knee strength.
For people who are more active, surgery to repair the torn ACL may be needed to allow the individual to get back to their prior activity level. In many cases, ACL repair involves reconstructing the ligament using a tissue graft.
Sources
American Academy of Orthopaedic Surgeons. Anterior Cruciate Ligament Injuries. http://orthoinfo.aaos.org/topic.cfm?topic=a00549
U.S. National Library of Medicine. Anterior Cruciate Ligament Injuries. https://www.nlm.nih.gov/medlineplus/ency/article/001074.htm
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