Anterior cruciate ligament injury

Overview 
Theory 
Diagnosis 
Management 
Follow up 
Resources 

Last reviewed: 5 Jun 2025

Last updated: 09 Jan 2025

Anterior cruciate ligament injury is typified by a sudden, painful, audible pop noise. The patient is typically unable to return to the ongoing sporting activity, and presents with joint instability, and rapid development of an effusion (hemarthrosis).

Often tender at lateral femoral condyle, lateral tibial plateau, and tibiofemoral joint lines.

A positive Lachman test is most accurate right after the injury and the pivot shift test is more useful in subacute or chronic cases.

History and physical exam usually provide an accurate diagnosis.

X-rays obtained to rule out avulsion fractures or other related conditions, but do not directly identify ACL injury. Magnetic resonance imaging delineates ACL tears, along with associated injury to the menisci and other structures.

Initial treatment for most patients consists of protection, rest, ice, compression, elevation, and analgesia (as appropriate). Subsequent treatment varies by an individual patient's health and fitness status and goals. Treatment may range from minimal or no additional intervention to bracing, physical therapy, and activity modification, and to surgical reconstruction (either early or delayed).

Definition

A torn anterior cruciate ligament (ACL) usually occurs as a result of an acute noncontact deceleration injury, forceful hyperextension, or excessive rotational forces about the knee.[1][2] The ligament may be completely torn, partially torn, or avulsed from its origin or insertion. The ACL is the primary restraint to excessive anterior translation and rotation of the tibia on the femur; therefore, complete ACL disruption typically results in dynamic knee instability or the inability to respond to quick changes in position.[3]

History and exam

Key diagnostic factors

audible pop
rapid knee swelling
inability to return to the ongoing sporting activity
sensation of knee instability or buckling
pain
positive Lachman test
positive pivot shift maneuver

Full details

Other diagnostic factors

tenderness at lateral femoral condyle, lateral tibial plateau
positive anterior drawer test

Full details

Risk factors

acute trauma
female sex (after puberty)
poor technique for landings
history of previous ACL injury
aggressive athlete with higher skill level
use of cleats or spikes
rough or uneven playing surface
ground condition/weather
fatigue
adolescent, young adults, and middle-aged athletes

Full details

Diagnostic tests

1st tests to order

x-rays

Full details

Tests to avoid

Full details

Tests to consider

MRI
arthroscopy

Full details

Treatment algorithm

ACUTE

sedentary patients

moderate intensity demands

intense dynamic demands

Contributors

Authors

Philip H. Cohen, MD

Clinical Assistant Professor of Medicine

Robert Wood Johnson Medical School

University of Medicine and Dentistry of New Jersey

Piscataway

Disclosures

PHC has been reimbursed by MCE Conferences for providing lectures and workshops in sports medicine.

Peer reviewers

James C. Puffer, MD

Professor

University of Kentucky School of Medicine

President and Chief Executive Officer

American Board of Family Medicine

Lexington

Disclosures

JCP declares that he has no competing interests.

Jung-Ro Yoon, MD

Director

Department of Orthopedic Surgery

Seoul Veterans Hospital

Seoul

South Korea

Disclosures

JRY declares that she has no competing interests.

References

Our in-house evidence and editorial teams collaborate with international expert contributors and peer reviewers to ensure that we provide access to the most clinically relevant information possible.

Key articles

Arundale AJH, Bizzini M, Giordano A, et al. Exercise-Based Knee and Anterior Cruciate Ligament Injury Prevention. J Orthop Sports Phys Ther. 2018 Sep;48(9):A1-A42.Full text Abstract

American Academy of Orthopaedic Surgeons. Management of anterior cruciate ligament injuries: evidence-based clinical practice guideline. Aug 2022 [internet publication].Full text

Padua DA, DiStefano LJ, Hewett TE, et al. National Athletic Trainers' Association Position Statement: Prevention of Anterior Cruciate Ligament Injury. J Athl Train. 2018 Jan;53(1):5-19.Full text Abstract

van Melick N, van Cingel RE, Brooijmans F, et al. Evidence-based clinical practice update: practice guidelines for anterior cruciate ligament rehabilitation based on a systematic review and multidisciplinary consensus. Br J Sports Med. 2016 Dec;50(24):1506-15.Full text Abstract

Reference articles

A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.

Differentials
- Medial collateral ligament (MCL) sprain
- Posterior collateral ligament (PCL) sprain
- Lateral collateral ligament (LCL) sprain
More Differentials
Guidelines
- AAOS management of anterior cruciate ligament injuries
- ACR appropriateness criteria - acute trauma to the knee
More Guidelines
Patient information
Anterior cruciate ligament injury
More Patient information
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Anterior cruciate ligament injury

Summary

Definition

History and exam

Key diagnostic factors

Other diagnostic factors

Risk factors

Diagnostic tests

1st tests to order

Tests to avoid

Tests to consider

Treatment algorithm

sedentary patients

moderate intensity demands

intense dynamic demands

Contributors

Authors

Philip H. Cohen, MD

Disclosures

Peer reviewers

James C. Puffer, MD

Disclosures

Jung-Ro Yoon, MD

Disclosures

References

Key articles

Reference articles

A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.

Differentials

Guidelines

Patient information

Log in or subscribe to access all of BMJ Best Practice

Log in or subscribe to access all of BMJ Best Practice

Log in to access all of BMJ Best Practice