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ACL Tear

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Other Names

  • Anterior Cruciate Ligament Injury
  • Anterior Cruciate Ligament Tear
  • ACL Tear
  • ACL Partial Tear
  • ACL Sprain
  • ACL Injury
  • Tibial Spine Fracture
  • Segond Fracture
  • Tibial eminence avulsion fracture



  • ACL is the most commonly injured knee ligament
    • Account for up to 64% of athletic knee injuries in cutting and pivoting sports (need citation)
  • Incidence
    • In the general population of approximately 1 in 3500 (need citation)
  • Cost
    • 120,000–200,000 ACL reconstructions (ACLRs) performed annually in the United States[1]
    • Cost of around 1.7 billion US dollars annually
  • Pediatric considerations
    • Tibial Spine Fractures are rare, incidence of 3 per 100,000 pediatric trauma cases per year[2]
    • Similar incidence in males and females
    • Occurs in children from age 8 to 14[3]


Tibial spine or eminence avulsion fracture suggestive of ACL tear.
  • Tear location
    • Skeletally mature athlete likely to have mid-substance tear
    • Young, skeletally immature athlete more likely to have at the origin of the femur


  • Noncontact
    • Majority of injuries occur during noncontact mechanism (60-70% of ACL injuries)[4]
    • Typically sustained when a running or jumping athlete suddenly decelerates, changes direction (eg, cutting), pivots or lands
    • Leads to rotation, lateral bending (ie, valgus stress) of the knee, anterior translation of the tibia on the femur
    • Often encompass an ill-timed neuromuscular firing of structures around the knee
  • Indirect contact
    • Occur when a person or object strikes a part of the body other than the knee itself
  • Direct contact
    • Defined as injury sustained when a person or object strikes the knee directly
    • Most often causing hyperextension or valgus deformation of the knee
    • Example: player's foot is planted, opponent strikes him on the lateral aspect of the planted leg
  • High speed trauma
    • Uncommon but can happen from MVC

Anatomy of the Anterior Cruciate Ligament

  • Extends from the lateral femoral condyle to the anterior medial aspect of the tibia[5]
  • Acts as primary passive restraint to anterior translation of the tibia on the femur
  • The bands of the ACL act as a biomechanical restraint in rotational and frontal planes
  • It assists with knee stability during running, jumping, cutting or pivoting.

Associated Injuries

Risk Factors

  • Female
    • Female > Male
    • Ratio ~4.5:1 (need citation)
    • Female soccer, basketball players sustain significantly more ACL injuries than male counterparts[6]
    • More female injuries at a younger age[7]
    • Tend to injury supporting leg/ non-dominant leg
  • Male
    • Tend to injure dominant/ kicking leg (need citation)
  • ACL Tears by Sport (Gornitzky et al) [8]
    • Football (0.089 per 1000 exposures)
    • Lacrosse (0.058)
    • Soccer (0.040)
    • Basketball (0.024)
    • Wrestling (0.021)
  • Additional sports with higher risk
    • Alpine skiing
    • Tennis
  • Anatomic
  • Neuromuscular control
    • Increased risk for ACL injuries[10]
      • Ligament dominance
      • Quadriceps dominance
      • Leg dominance
      • Trunk dominance
    • Female athletes
      • Increased risk with dynamic valgus position, abduction of lower extremities
    • Dynamic Valgus Landing

Differential Diagnosis

Differential Diagnosis Knee Pain

Clinical Features


  • Careful description of mechanism of injury
  • Patients will often describe sudden changes in the direction of movement, rapid stopping, jumping and landing abnormally
  • Less commonly a direct blow to the lateral knee
  • Patients usually feel a "pop"
  • Will describe a buckling sensation
  • Will also endorse pain, typically "deep"
  • Also swelling, loss of range of motion and difficulty ambulating
  • Will endorse instability, knee "giving out"
  • Causes of instability include squatting, pivoting, lateral movement, walking down stairs

Physical Exam: Physical Exam Knee

  • Gait: Quadriceps avoidance (does not actively extend knee)
  • Very important to compare to unaffected knee
  • Joint effusion: ~70% of patients with acute knee and hemarthrosis have ACL tear[11]
  • Note presence and degree of effusion may limit exam
  • Range of motion is typically restricted with a resting position of 20-30° knee flexion
  • There may be tenderness along the tibial plateau
  • If there is a tibial spine fracture, there may be a block to full extension

Special Tests


Sagittal view of knee MRI demonstrating ACL tear
Coronal view of knee MRI demonstrating bone bruise suggesting acute injury


  • Standard Radiographs Knee
    • Screening tool in the setting of suspected ACL injury
  • Segund Fracture
    • Avulsion fracture at the latera aspect of the proximal tibia
    • Attachment site of the lateral collateral ligament and/or biceps femoris tendon
  • Tibial Spine Fracture
    • Fleck of bone off the center of tibial plateau that appears avulsed
    • Optimal beam projection: AP with 5° caudad tilt matching the slope of the proximal tibia[12]


  • Imaging modality of choice in the setting of suspected ACL injury
  • Primary Findings
    • Edema
    • Increased signal (T2 weighted, proton density images)
    • Discontinuity of the fibers
    • Change in the expected course of the ACL
    • Tears usually occur within the midportion of the ligament
  • Secondary Findings
    • Bone marrow edema/ contusion
    • Joint effusion
    • Segund Fracture (discussed above)
  • Without contrast
    • Sensitivity 86%
    • Specificity 95%
  • Arthrogram (rarely used)
    • Sensitivity 92-100%
    • Specificity 95-100%


  • Can be used to aid in the diagnosis
    • Ultrasound is best at detecting complete ACL rupture
    • Sensitivity is likely more limited than MRI.
  • Meta-analysis[13]
    • Sensitivity: 90.0% (95% CI: 77–96)
    • Specificity: 97% (95% CI: 90–99)
    • LR+: 31.08 (95% CI: 8.75–110.41)
    • LR-: 0.11 (95% CI: 0.05–0.24)
    • Post-test probability: 89% (3%)
    • Diagnostic OR: 288.81 (95% CI: 78.51–1062.48)


  • No current widely accepted classification system exists



  • Neuromuscular control
    • Increase dynamic knee stability translates to decreased incidence of noncontact ACL injury in female athletes
    • Improve pre- and mid-stance neuromuscular activation patterns, decrease joint motion and protect the ACL
  • Posterior chain muscle group
    • Involves strengthening such as the gluteus maximus, gluteus medius, gluteus minimus, and hamstings
    • Reduces the load to the ACL by controlling frontal plane motion and improving neuromuscular control[14]
    • Benefit likely greatest in preadolescent or early adolescent female athletes[15]
  • Screening
    • Microsoft kinect can be used for screening dynamic valgus during drop vertical jump test[16]


  • Indications
    • Patients who are not good surgical candidates
    • Low demand patients with decreased laxity
    • Recreational athlete not participating in cutting/pivoting activities
    • Minimally displaced tibial spine fracture
  • Treatment includes


  • Indications
    • Vast majority of young, healthy adults
    • Displaced tibial spine fracture
  • Technique
    • ACL Repair
    • ACL Reconstruction
    • ACL revision reconstruction
  • Reconstruction sources
    • Hamstring Tendon (HT)
    • Bone-patellar Tendon-bone (BPTB)
    • Quadriceps Tendon (QT)
  • Double vs single bundle
    • Double bundle reconstructs AM, PL bundles to more closely reproduce native knee anatomy
    • Single bundle is used in smaller tibial insertions, severe bone bruising, arthritic changes or open physes
  • Biologic agents
    • Increasing interest in using biologic agents to augment repair or to treat stable partial tears
    • A few small studies suggest Platelet Rich Plasma may promote graft maturation, however this is controversial
    • The use of Stem Cell Therapy is highly debated and poorly understood

Rehab and Return to Play


  • General
    • No consensus regarding most effective rehabilitation program
  • General modalities and approach
    • Cryotherapy (ice)
    • Gravity-assisted motion or continuous passive motion (constant mechanical movement by a machine)
    • Protective bracing
    • Electrical neuromuscular stimulation
    • Exercises (i.e., isometric, isotonic, and isokinetic) aimed at strengthening, balance, proprioception
    • Mitigation of the inflammatory response

3 Stage Approach

  • Acute
    • Used both following acute injury, immediate postoperative period
    • Goal: restore range of motion, maintain quadriceps strength, reduce inflammation
  • Recovery
    • Goal: improving lower limb muscle strength and functional stability
    • Typically lasts 3–6 weeks
  • Functional Phases
    • Begins 6 weeks postinjury or postoperatively
    • Goal: return the patient to his or her previous levels of function/activity
    • Goal: reduce the risk of re-injury

Return to Play/Work

  • General
    • No clear consensus on return to play guidelines
    • Premature return to play associated with graft failure, contralateral ACL tear
    • Recent trends favor a decelerated rehabilitation protocol with consideration of return to play in the realm of 8–12 months
  • Set of criteria for return to play
    • 8-12+ months from time from surgery
    • Absence of pain and effusion
    • Knee range of motion comparable to the contralateral limb
    • Negative Lachman or pivot shift test
    • Successful performance of hop tests at >85%–90% the performance of the contralateral limb
    • Jump and landing tasks such as the drop vertical jump without evidence of dynamic valgus

Prognosis and Complications


  • Nonoperative management
    • Tolerated poorly by young active adults, skeletal immature
    • Can lead to instability, chondral and meniscal injuries
  • Cochrane review compared surgical vs nonsurgical management[17]
    • No difference between surgery and conservative treatment in patient-reported knee scores at 2 and 5 years
    • However, in conservative group, 39% of patients had surgery at 2 years and 51% at 5 years.
  • Early vs delayed reconstruction
    • Shelbourne at al showed delayed (8-21 days) was superior to early (0-7) days reconstruction for quadriceps strength, terminal knee extension[18]
    • For this reason, there is a growing trend to use preoperative rehabilitation emphasizing quadriceps strength, knee range of motion
  • Concomitant meniscal repair
    • Saltzman et al found meniscal allograft transplantation (MAT) can provide significant improvements in clinical outcomes and enhancement in objective knee stability[19]
  • Early return to play
    • Increased risk of graft failure[20]
    • Increased risk of injury to contralateral ACL


  • Intra-operative
    • Graft-tunnel mismatch
    • Posterior wall blowout
  • Post-operative complications
  • Re-tear/ graft failure
    • Failure rates as high as 14% (adults), 28% (males under 18)[21]
    • May occur due to
      • Tunnel malposition
      • Inadequate graft fixation, hardware failure
      • Graft-screw divergence >30°
      • Attritional graft failure
      • Graft less then 8mm in width
      • Intra-articular femoral bone plug dislodgement
      • Missed diagnosis of concomitant ligamentous injuries
      • Over-aggressive or improper rehab
    • Increased risk
      • Increased graft irradiation
      • Posterior tibial tunnel placement[22]
      • Meniscal deficiency, especially posterior horn of medial meniscus[23]
      • Younger patient age
    • Reduced risk
      • BPTB had lowest failure rate[24]
      • Increasing age[25]
  • Contralateral ACL tear
    • As high as 8% during 12 years follow up[24]
  • Chronic complications
    • Meniscal Tear
      • Not necessarily present on initial injury but occurs due altered biomechanics of knee
    • Chondromalacia
    • Knee Osteoarthritis
    • Arthrofibrosis
      • Most commmon complication following ACL repair
    • Altered knee kinematics and gait
    • Muscle Weakness
    • Reduced functional performance
    • Inability to return to sport
    • Loss of range of motion
    • Infrapatellar contracture syndrome
    • Patella Tendon Rupture
    • Reflex Sympathetic Dystrophy
    • Patellar Fracture
    • Tunnel osteolysis
    • Local nerve irritation
    • Cyclops lesion

See Also




  1. 7. Kim S, Bosque J, Meehan JP, Jamali A, Marder R. Increase in outpatient knee arthroscopy in the United States: A comparison of national surveys of ambulatory surgery, 1996 and 2006. J Bone Joint Surg Am. 2011;93:994–1000
  2. Scrimshire, A. B., et al. "Management and outcomes of isolated paediatric tibial spine fractures." Injury 49.2 (2018): 437-442.
  3. Gans, Itai, Keith D. Baldwin, and Theodore J. Ganley. "Treatment and management outcomes of tibial eminence fractures in pediatric patients: a systematic review." The American Journal of Sports Medicine 42.7 (2014): 1743-1750.
  4. Boden, Barry P., et al. "Mechanisms of anterior cruciate ligament injury." Orthopedics 23.6 (2000): 573-578.
  5. Kiapour AM, Murray MM. Basic science of anterior cruciate ligament injury and repair. Bone Joint Res. 2014;3:20–31
  6. Prodromos, Chadwick C., 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: The Journal of Arthroscopic & Related Surgery 23.12 (2007): 1320-1325.
  7. DeFrancesco, Christopher J., et al. "Challenges in the management of anterior cruciate ligament ruptures in skeletally immature patients." JAAOS-Journal of the American Academy of Orthopaedic Surgeons 26.3 (2018): e50-e61.
  8. Gornitzky AL, Lott A, Yellin JL, Fabricant PD, Lawrence JT, Ganley TJ. Sport-Specific Yearly Risk and Incidence of Anterior Cruciate Ligament Tears in High School Athletes: A Systematic Review and Meta-analysis. Am J Sports Med. 2016 Oct;44(10):2716-2723. Epub 2015 Dec 11.
  9. Christensen JJ, Krych AJ, Engasser WM, Vanhees MK, Collins MS, Dahm DL, et al. Lateral tibial posterior slope is increased in patients with early graft failure after anterior cruciate ligament reconstruction. Am J Sports Med. 2015;43:2510–4.
  10. Hewett TE, Ford KR, Hoogenboom BJ, Myer GD. Understanding and preventing ACL injuries: Current biomechanical and epidemiologic considerations - Update 2010. N Am J Sports Phys Ther. 2010;5:234–51
  11. Maffulli, N., et al. "Acute haemarthrosis of the knee in athletes. A prospective study of 106 cases." The Journal of Bone and Joint Surgery. British volume 75.6 (1993): 945-949.
  12. Egol, Kenneth, Kenneth J. Koval, and Joseph D. Zuckerman. Handbook of fractures. Lippincott Williams & Wilkins, 2012.
  13. Wang, Jianhong, et al. "The role of ultrasonography in the diagnosis of anterior cruciate ligament injury: a systematic review and meta-analysis." European Journal of Sport Science 18.4 (2018): 579-586.
  14. Stone EE, Butler M, McRuer A, Gray A, Marks J, Skubic M, et al. Evaluation of the Microsoft Kinect for screening ACL injury. Conf Proc IEEE Eng Med Biol Soc. 2013;2013:4152–5.
  15. Hewett TE, Myer GD, Ford KR, Paterno MV, Quatman CE. Mechanisms, prediction, and prevention of ACL injuries: Cut risk with three sharpened and validated tools. J Orthop Res. 2016;34:1843–55.
  16. Gray AD, Marks JM, Stone EE, Butler MC, Skubic M, Sherman SL. Validation of the Microsoft Kinect as a portable and inexpensive screening tool for identifying ACL injury risk. Orthop J Sports Med. 2014;2(2 Suppl)
  17. Monk AP, Davies LJ, Hopewell S, Harris K, Beard DJ, Price AJ, et al. Surgical versus conservative interventions for treating anterior cruciate ligament injuries. Cochrane Database Syst Rev. 2016;4:CD011166.
  18. Shelbourne KD, Foulk DA. Timing of surgery in acute anterior cruciate ligament tears on the return of quadriceps muscle strength after reconstruction using an autogenous patellar tendon graft. Am J Sports Med. 1995;23:686–9
  19. Saltzman BM, Meyer MA, Weber AE, Poland SG, Yanke AB, Cole BJ, et al. Prospective clinical and radiographic outcomes after concomitant anterior cruciate ligament reconstruction and meniscal allograft transplantation at a mean 5-year followup. Am J Sports Med. 2017;45:550–62.
  20. Ellman MB, Sherman SL, Forsythe B, LaPrade RF, Cole BJ, Bach BR, Jr, et al. Return to play following anterior cruciate ligament reconstruction. J Am Acad Orthop Surg. 2015;23:283–96.
  21. Webster KE, Feller JA. Exploring the high reinjury rate in younger patients undergoing anterior cruciate ligament reconstruction. Am J Sports Med. 2016;44:2827–32.
  22. Inderhaug E, Raknes S, Østvold T, Solheim E, Strand T. Increased revision rate with posterior tibial tunnel placement after using the 70-degree tibial guide in ACL reconstruction. Knee Surg Sports Traumatol Arthrosc. 2017;25:152–8
  23. Parkinson B, Robb C, Thomas M, Thompson P, Spalding T. Factors that predict failure in anatomic single-bundle anterior cruciate ligament reconstruction. Am J Sports Med. 2017;45:1529–36.
  24. 24.0 24.1 Ho B, Edmonds EW, Chambers HG, Bastrom TP, Pennock AT. Risk factors for early ACL reconstruction failure in pediatric and adolescent patients: A review of 561 cases. J Pediatr Orthop. 2016
  25. Ponce BA, Cain EL, Jr, Pflugner R, Fleisig GS, Young BL, Boohaker HA, et al. Risk factors for revision anterior cruciate ligament reconstruction. J Knee Surg. 2016;29:329–36.
Created by:
John Kiel on 7 July 2019 05:43:30
Last edited:
22 March 2023 14:53:29