- The anterior cruciate ligament (ACL) is one of the major stabilizers of the knee:
- It prevents excessive anterior translation and internal rotation of the tibia in relation to the femur.
- During dynamic movement, the ACL and posterior cruciate ligament (PCL) work together to stabilize the knee.
- ACL injuries are common and can occur through noncontact or contact mechanisms. >70% of ACL injuries are caused by noncontact forces (1).
- Partial tears of the ACL can occur, but complete tears are far more common.
- Female athletes are at 2–5 times higher risk of ACL tear, particularly in soccer, basketball, and skiing.
- ACL injury is associated with early onset of knee osteoarthritis, regardless of surgical or nonsurgical treatment (2)[B].
- 250,000 ACL injuries annually in the US (1)
- Female athletes incidence 2–5-fold > male athletes
- Greater incidence of noncontact ACL injuries in sports requiring cutting, pivoting, and rapid deceleration, such as basketball and soccer
- Young athletes aged 15–25 years sustain >50% of all ACL injuries.
- >2/3 of patients with complete ACL tear have associated menisci and/or articular cartilage injury (1).
- Must be concerned about physeal injuries in the skeletally immature
- The incidence of ACL tears in patients with open physes has increased in recent years.
- ACL injury rates increase for both boys and girls beginning at age 11 years.
- No single risk factor correlates directly with higher ACL injury rates in female athletes. Likely multifactorial etiology:
- Sex hormones:
- Increased rate may be due to monthly hormonal fluctuations.
- No conclusive evidence linking a menstrual cycle phase to ACL injury risk
- Anatomic gender differences:
- Increased Q angle, increased genu valgum, narrower femoral notch size, smaller ACL
- Neuromuscular imbalances (increased quadriceps activation, decreased hamstring activity during landings)
- Movement patterns (sudden deceleration, change-of-direction cutting movements, landing from a jump in hyperextension)
- Sex hormones:
Familial tendency has been identified.
- Neuromuscular training with proprioceptive, plyometric, and strength exercises may reduce noncontact ACL injuries by 72% in female athletes if performed > once per week for >6 weeks (1,3)[B].
- No evidence that prophylactic knee bracing prevents ACL injuries
- Educate the patient about possible risk factors for ACL injury and provide instruction on neuromuscular training exercises.
- Noncontact mechanisms (torsional or hyperextension forces)
- Direct trauma (player, object on playing field), most often a valgus blow to the knee
Commonly Associated Conditions
- Meniscal tear
- Collateral ligament tear
- PCL tear
- Tibia or femur fractures
- Osteochondral injury
- Loose bodies
- Early-onset degenerative joint disease
May recall mechanism:
- Sudden deceleration
- Cutting, sudden change in direction
- Landing from a jump in extension
- Combination of mechanisms
- Contact with player, object
- May recall sudden pop or snap
- Sudden pain and giving way
- Marked effusion/hemarthrosis within 4–12 hours
- Decreased range of motion (ROM)
- Joint instability
- Difficulty bearing weight
- Inspect for malalignment (fracture, dislocation)
- Palpate for effusion
- Evaluate extensor mechanism integrity
- Evaluate ROM:
- Deficits may be secondary to pain, effusion, mechanical blocks (meniscal tear, loose body, torn ACL stump).
Diagnostic Tests and Interpretation
- Lachman test: Most sensitive and highly specific diagnostic test for ACL injury, especially in acute setting (4)[A]:
- Knee placed in 20–30° flexion. Tibia is translated anteriorly while the femur is stabilized with the opposite hand. Increased anterior translation compared with uninjured knee indicates injury. Lack of a solid endpoint indicates rupture.
- Pivot shift test: Lower sensitivity, but more specific for ACL tear than Lachman test (4)[B]:
- Knee placed in extension. Knee is flexed while applying a valgus and internal rotation stress. A positive test is subluxation at 20–40° of flexion.
- Anterior drawer test:
- Posterior drawer test assesses PCL integrity.
- McMurray test assesses for meniscal tears.
- Valgus/Varus stress test for medial collateral ligament/lateral collateral (MCL/LCL) integrity
Initial Imaging Approach
- Radiographs to rule out associated bony injury
- Anterior-posterior (AP), lateral, and tunnel views:
- Segond fracture: Avulsion fracture of the lateral capsular margin of the tibia
- Tibial eminence avulsion fracture
- Fracture of proximal tibia or distal femur
- Osteochondral injuries
- MRI is the gold standard for imaging ligamentous and intra-articular structures; MRI may show secondary signs of ACL injury. The sensitivity of MRI is 87–94%, specificity 88–93% (5).
- Secondary signs include: Bone contusion of the anterior femoral condyle and/or posterior tibial plateau, anterior translation of the tibia, an uncovered or displaced posterior horn of the lateral meniscus, PCL buckling, or a Segond fracture (an avulsion fracture of the lateral tibial condyle).
Surgical management should be considered in the active population, young or old.
- Meniscal injury
- Patellar dislocation/subluxation
- Tendon disruption
- PCL injury
- Collateral ligament injury
- Acute ligament sprains:
- Ibuprofen: 200–800 mg t.i.d.
- Naproxen: 375–500 mg b.i.d.
- Indomethacin: 25–50 mg t.i.d.
- Acute ligament sprains:
- Narcotics for severe pain (e.g., acetaminophen-hydrocodone)
- Contraindications/Precautions/Interactions: Refer to the manufacturer’s profile of each drug.
- Acute injury: PRICEMM therapy: Protection, Relative rest, Ice, Compression, Elevation, Medications, Modalities
- Crutches may be indicated until patient is able to ambulate without pain.
- Knee brace may be used initially for comfort. Use with caution.
- Aspiration of large effusion may be indicated to alleviate pain and increase ROM.
Management is based on anticipated activity level, associated injuries, coexisting medical conditions, and acute vs. long-standing ACL deficiency.
Issue for Referral
Surgical management should be considered in the active population.
- Physical therapy is recommended if an athlete chooses nonsurgical or surgical treatment. Nonsurgical physical therapy is focused on restoring ROM, strength, and proprioception.
- Preoperative phase:
- Increase ROM, minimize inflammation
- Early postoperative phase: Weeks 2–4:
- ROM: Full extension is the most important goal. Rehabilitation begins immediately.
- Progress to full weight bearing.
- Intermediate postoperative phase: Weeks 4–12:
- ROM: Full flexion, hyperextension
- Quadriceps and hamstring strengthening proprioceptive training, normalize gait
- Late postop phase: 2–3 months postop:
- Straight-line running
- Increase speed, duration over 6–8 weeks.
- Progress to cutting and sport-specific drills.
- Strength and proprioceptive training
- Surgical vs. conservative management depends on patient’s activity level, age, associated injuries, and presence of osteoarthritis.
- Insufficient evidence for ACL reconstructive surgery vs. conservative management in the skeletally immature patient
- Insufficient evidence from randomized trials comparing surgical vs. nonoperative management of ACL injuries in adults based on studies in the 1980s (6)[A]
- In young, active adults with acute ACL tears, rehabilitation plus early ACL repair was not superior to a strategy of initial rehabilitation with delayed repair if rehab alone failed. In fact, the latter strategy led to an overall reduction of ACL reconstructions (7)[A].
- Reconstruction techniques:
- Bone-patella tendon-bone autograft
- Hamstring autograft
- Allograft tendon (from cadaver)
- No consistent significant differences in outcome between patellar tendon and hamstring tendon autografts (8)[A]
- Concomitant meniscal tears are repaired at the time of ACL reconstruction.
- ROM exercises to regain full flexion and extension
- Advance activity as tolerated.
Assess functional status, rehabilitative exercise compliance, and pain control at follow-up visit.
- Secondary meniscal and articular cartilage injury
- Early-onset degenerative arthritis
- Surgical risks:
- Infection, pulmonary embolism (PE), subsequent ACL graft rupture, laxity due to failure of graft remodeling
- Cascio BM, Culp L, Cosgarea AJ. Return to play after anterior cruciate ligament reconstruction. Clin Sports Med. 2004;23(3):395–408, ix.
- Jackson JL, O'Malley PG, Kroenke K. Evaluation of acute knee pain in primary care. Ann Intern Med. 2003;139(7):575–588.
- Spindler KP, Kuhn JE, Freedman KB, et al. Anterior cruciate ligament reconstruction autograft choice: Bone-tendon-bone versus hamstring: does it really matter? A systematic review. Am J Sports Med. 2004;32(8):1986–1995.
Algorithm: Knee pain
844.2 Sprain of cruciate ligament of knee
- S83.519A Sprain of anterior cruciate ligament of unsp knee, init
- S83.519D Sprain of anterior cruciate ligament of unsp knee, subs
- S83.519S Sprain of anterior cruciate ligament of unsp knee, sequela
- S83.511A Sprain of anterior cruciate ligament of right knee, init
- S83.511D Sprain of anterior cruciate ligament of right knee, subs
- S83.511S Sprain of anterior cruciate ligament of right knee, sequela
- S83.512A Sprain of anterior cruciate ligament of left knee, init
- S83.512D Sprain of anterior cruciate ligament of left knee, subs
- S83.512S Sprain of anterior cruciate ligament of left knee, sequela
- 444470001 Injury of anterior cruciate ligament
- 127292004 sprain of anterior cruciate ligament of knee (disorder)
- 239725005 Rupture of anterior cruciate ligament (disorder)
- 209520004 partial tear, knee, anterior cruciate ligament (disorder)
- 209629006 complete tear, knee, anterior cruciate ligament (disorder)
- Lachman test: Most sensitive and highly specific diagnostic test for ACL injury, especially in acute setting (4)[A]
- Pivot shift test: Less sensitive but more specific for ACL tear than the Lachman test (4)[B]
- Anterior drawer test: Low sensitivity for ACL integrity, especially in acute setting (4)[A]
- 2/3 of complete ACL tears have associated meniscal or articular injuries.
Kylee Eagles, DO
J. Herbert Stevenson, MD
- Silvers HJ, Mandelbaum BR. Prevention of anterior cruciate ligament injury in the female athlete. Br J Sports Med. 2007;41(Suppl 1):i52–i59. [PMID:17609222]
- Christiansen BA, Anderson MJ, Lee CA, et al. Musculoskeletal changes following non-invasive knee injury using a novel mouse model of post-traumatic osteoarthritis. Osteoarthr Cartil. 2012;20(7):773–782. Epub 2012 Apr 21.
- Hewett TE, Ford KR, Myer GD. Anterior cruciate ligament injuries in female athletes: Part 2, a meta-analysis of neuromuscular interventions aimed at injury prevention. Am J Sports Med. 2006;34:490–498. [PMID:16382007]
- Jain DK, Amaravati R, Sharma G. Evaluation of the clinical signs of anterior cruciate ligament and meniscal injuries. Indian J Orthop. 2009;43(4):375–378. [PMID:19838388]
- Vincken PW, ter Braak BP, van Erkell AR, et al. Effectiveness of MR imaging in selection of patients for arthroscopy of the knee. Radiology. 2002;223(3):739–746. [PMID:12034943]
- Linko E, Harilainen A, Malmivaara A, et al. Surgical versus conservative interventions for anterior cruciate ligament rupture in adults. Cochrane Database Syst Rev. 2005;Issue 4.
- Frobell RB, Roos EM, Roos HP, et al. A randomized trial of treatment for acute anterior cruciate ligament tears. N Engl J Med. 2010;363(4):331–342. [PMID:20660401]
- Mohtadi NG, Chan DS, Dainty KN, et al. Patellar tendon versus hamstring tendon autograft for anterior cruciate ligament rupture in adults. Cochrane Database Syst Rev. 2011;(9):CD005960. Epub 2011 Sep 7.
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