Cruciate ligament injury - anterior; ACL tear; Knee injury - anterior cruciate ligament (ACL)
An anterior cruciate ligament injury is the over-stretching or tearing of the anterior cruciate ligament (ACL) in the knee. A tear may be partial or complete.
The knee joint is located where the end of the thigh bone (femur) meets the top of the shin bone (tibia).
Four main ligaments connect these two bones:
Women are more likely to have an ACL tear than men.
An ACL injury can occur if you:
Basketball, football, soccer, and skiing are common sports linked to ACL tears.
ACL injuries often occur with other injuries. For example, an ACL tear often occurs along with tears to the MCL and the shock-absorbing cartilage in the knee (meniscus).
Most ACL tears occur in the middle of the ligament, or the ligament is pulled off the thigh bone. These injuries form a gap between the torn edges, and do not heal on their own.
Early symptoms:
Those who have only a mild injury may notice that the knee feels unstable or seems to "give way" when using it.
See your health care provider if you think you have an ACL injury. Do not play sports or other activities until you have seen your provider and have been treated.
Your provider may send you to get an MRI of the knee. It can confirm the diagnosis. It may also show other knee injuries.
First aid for an ACL injury may include:
You also may need:
Some people can live and function normally with a torn ACL. However, most people complain that their knee is unstable and may "give out" with physical activity. An unstable knee after an ACL tear can lead to further knee damage. You are also less likely to be able to return to the same level of sports if you have a torn ACL.
Contact your provider right away if you have a serious knee injury.
Get immediate medical attention if the foot is cool and blue after a knee injury. This means that the knee joint may be dislocated, and blood vessels to the foot may be injured. This is a medical emergency.
Use proper techniques when playing sports or exercising. Some college sports programs teach athletes how to reduce stress placed on the ACL. This involves a series of warm up exercises and jumping drills. There are jumping and landing exercises that have been shown to reduce ACL injuries.
The use of knee braces during vigorous athletic activity (such as football) is controversial. It has been shown to reduce the number of certain knee ligament injuries, but not specifically ACL injuries.
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Brotzman SB. Anterior cruciate ligament injuries. In: Giangarra CE, Manske RC, eds. Clinical Orthopaedic Rehabilitation: A Team Approach. 4th ed. Philadelphia, PA: Elsevier; 2018:chap 47.
Cheung EC, McAllister DR, Petrigliano FA. Anterior cruciate ligament injuries. In: Miller MD, Thompson SR, eds. DeLee, Drez, & Miller's Orthopaedic Sports Medicine. 5th ed. Philadelphia, PA: Elsevier; 2020:chap 98.
Gokeler A, Dingenen B, Hewett TE. Rehabilitation and return to sport testing after anterior cruciate ligament reconstruction: where are we in 2022? Arthrosc Sports Med Rehabil. 2022;4(1):e77-e82. PMID: 35141539 pubmed.ncbi.nlm.nih.gov/35141539/.
Kalawadia JV, Guenther D, Irarrázaval S, Fu FH. Anatomy and biomechanics of the anterior cruciate ligament. In: Prodomos CC. The Anterior Cruciate Ligament: Reconstruction and Basic Science. 2nd ed. Philadelphia, PA: Elsevier; 2018:chap 1.
Miller RH, Azar FM. Knee injuries. In: Azar FM, Beaty JH, eds. Campbell's Operative Orthopaedics. 14th ed. Philadelphia, PA: Elsevier; 2021:chap 45.
BACK TO TOPReview Date: 6/17/2024
Reviewed By: C. Benjamin Ma, MD, Professor, Chief, Sports Medicine and Shoulder Service, UCSF Department of Orthopaedic Surgery, San Francisco, CA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
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