Anterior Cruciate Ligament Injury
An anterior cruciate ligament (ACL) injury is a tear in the ACL ligament. The ACL is located in the middle of the knee joint. It connects the lower leg bone to the thigh bone. It stabilizes the knee and prevents the lower leg bone from sliding too far forward at the knee.
The ACL ligament can become strained or torn when a strong force is applied to it. This can happen during sports or other high-stress activity.
Treatment depends on the severity of the injury.
Anterior Cruciate Ligament Injury
ACL injury occurs when your knee gets twisted or during a hard landing from a jump. It can also happen with:
- Sudden stops or changes in direction
- Sidestepping or pivoting
- Direct contact
ACL injuries are more common in women. Other factors that increase your chance of ACL injury include:
- Weak knee structure
- Muscle strength imbalance between the quadriceps and hamstrings
- Playing sports that require sudden changes of direction and deceleration
- Use of incorrect technique for cutting, planting, pivoting, or jumping
Symptoms may include:
- A popping sound at the time of the injury
- Pain and swelling in the knee
- Loss of full range of motion
- Weakness or instability in the knee
- Difficulty walking
The doctor will ask about your symptoms and how you injured your knee. A physical exam will be done.
Tests may include:
- Arthroscopy —a thin, lighted tube inserted through a small incision in the knee to look at the structures inside the knee
Ligament sprains are graded according to their severity:
- Grade 1—Mild ligament damage.
- Grade 2—Partial tearing of the ligament.
- Grade 3—Complete tearing of the ligament.
Talk with your doctor about the best treatment plan for you. Recovery time ranges depending on the grade of your injury. Treatment steps may include:
Your ligament will need time to heal. Avoid activities that place extra stress on the knee:
- Do not do activities that cause pain. This includes running, jumping, and weight lifting using the legs.
- Do not play sports until your doctor has said it is safe to do so.
Your doctor may recommend a knee brace to stabilize the knee, and crutches to keep extra weight off your leg.
Apply an ice or a cold pack to the area for 15-20 minutes, four times a day, for several days after the injury. Do not apply the ice directly to your skin. Wrap the ice or cold pack in a towel.
Pain Relief Medications
To manage pain, your doctor may recommend:
- Over-the-counter medication, such as aspirin , ibuprofen , or acetaminophen
- Topical pain medication—creams or patches that are applied to the skin
- Prescription pain relievers
Compression can help prevent more swelling. Your doctor may recommend an elastic compression bandage around your knee. Be careful not to wrap the bandage too tight.
Use heat only when you are returning to physical activity. Heat may then be used before stretching or getting ready to play sports to help loosen the ligament.
When the acute pain is gone, start gentle stretching as recommended. Stay within pain limits. Hold each stretch for about 10 seconds and repeat six times. Stretch several times a day.
To reduce your chance of injuring the ACL, take these steps:
- Plyometrics , a form of jumping exercises, can be used to train and strengthen the leg muscles for jumping and landing.
- When jumping and landing, or turning and pivoting, your hips and knees should be bent, not straight.
- Strengthen both the quadriceps and the hamstrings.
- Maintain proper technique when exercising or playing sports.
American Academy of Orthopaedic Surgeons
American Orthopaedic Society for Sports Medicine
Canadian Orthopaedic Association
Canadian Orthopaedic Foundation
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ACL Injury: Does It Require Surgery? American Academy of Orthopaedic Surgeons website. Available at: http://orthoinfo.aaos.org/topic.cfm?topic=A00297http://orthoinfo.aaos.org/topic.cfm?topic=A00297. Updated September 2009. Accessed May 3, 2013.
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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 February 2012. Accessed May 3, 2012.
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 May 3, 2013.
7/6/2009 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed/what.php: 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.
Last reviewed March 2013 by John C. Keel, MD
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.