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Anterior cruciate ligament injury

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Updated 2023 APTA guidelines for the prevention of anterior cruciate ligament injury.



ACL injury is a tear or sprain of the ACL, a major ligament in the knee that helps stabilize the joint.
ACL injury is commonly caused by sports-related activities that involve sudden stops, changes in direction, or direct blows to the knee. These injuries are particularly prevalent in sports such as football, basketball, skiing, and soccer.
The incidence of ACL injury in the US is estimated at 5.3 per 100,000 person-years.
Disease course
Clinically, ACL injury typically presents with immediate pain in the knee, which is often accompanied by a popping sensation. This is usually followed by swelling within a few hours. Patients may also experience a feeling of instability or "giving way" in the knee, possible bruising, and difficulty walking due to pain or instability.
Prognosis and risk of recurrence
The prognosis of ACL injury depends on the severity of the injury and the treatment approach. ACL injuries do not heal on their own, but they can be effectively managed with rehabilitation or surgical interventions.


Key sources

The following summarized guidelines for the evaluation and management of anterior cruciate ligament injury are prepared by our editorial team based on guidelines from the American Physical Therapy Association (APTA 2023), the European Bone and Joint Infection Society (EBJIS 2023), the American Academy of Orthopaedic Surgeons (AAOS 2022), the American College of Radiology (ACR 2020), and the American Academy of ...
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Diagnostic investigations

History and physical examination: as per AAOS 2022 guidelines, elicit a relevant history and perform a focused musculoskeletal examination of the lower extremities in the evaluation for an ACL injury.
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  • Knee radiography

  • Knee MRI

  • Knee CT

Nonpharmacologic interventions

Conservative management: as per AAFP 2010 guidelines, consider offering a trial of conservative management in patients with few giving-way episodes, near normal ROM on knee extension, minimal or no meniscal damage on MRI, strong quadriceps femoris, and no difficulty performing the crossover hop test.

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  • Functional knee bracing

Therapeutic procedures

Knee joint aspiration: as per AAOS 2022 guidelines, consider performing knee joint aspiration of painful, tense effusions after a knee injury.

Surgical interventions

ACL reconstruction, indications: as per AAOS 2022 guidelines, consider performing ACL reconstruction in order to lower the risk of future meniscus pathology or procedures, particularly in younger and/or more active patients, and to improve long-term pain and function.

More topics in this section

  • ACL reconstruction (timing)

  • ACL reconstruction (choice of technique)

  • ACL reconstruction (choice of graft)

  • MCL reconstruction

  • Meniscal repair

Specific circumstances

Patients with postoperative septic arthritis: as per EBJIS 2023 guidelines, suspect septic arthritis after reconstruction of the ACL in the presence of a delayed ROM recovery, increased warmth or swelling, wound drainage and arthrofibrosis, unusual pain, and systemic symptoms, such as fever and malaise. Confirm the diagnosis in the presence of purulent discharge/aspirate, sinus tract communication with the joint, and intra-articular pus.
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Preventative measures

Education programs: as per APTA 2023 guidelines, offer exercise-based knee injury prevention programs in athletes to prevent knee and ACL injuries, such as:
for all knee inuries: 11+ and FIFA 11, HarmoKnee, Knäkontroll, and programs used by Emery and Meeuwisse, Goodall et al, Junge et al, LaBella et al, Malliou et al, Olsen et al, Pasanen et al, Petersen et al, and Wedderkopp et al
for ACL injuries: HarmoKnee, Knäkontroll, Prevent Injury and Enhance Performance, and Sportsmetrics, and programs used by Caraffa et al, Heidt et al, LaBella et al, Myklebust et al, Olsen et al, and Petersen et al.
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  • Prophylactic knee bracing

Follow-up and surveillance

Return to sport activities: as per AAOS 2022 guidelines, consider obtaining functional evaluation, such as the hop test, as one factor to determine return to sport after ACL reconstruction.