An anterior cruciate ligament (ACL) injury is one of the most common severe knee injuries in sports. The purpose of this review was to summarize the studies that directly quantified in vivo ACL loading as a function of knee motion in healthy individuals during static, slow-speed and athletic tasks.
A systematic review of the literature in multiple databases was conducted using different combinations of the terms “anterior cruciate ligament” or “ACL” and “in vivo” combined with “tensile” “strain” “stress” “force” and “loading”.
A total of 27 studies were identified. Eleven studies utilized strain sensors, while 16 studies applied imaging techniques. The numbers of studies for static or semi-static postures, slow-speed tasks, and athletic tasks were 12, 11 and 4, respectively.
There were strong and negative correlations between ACL elongation and knee flexion angles across different tasks. Peak ACL elongation mostly occurred when the knee flexion angle was minimal. Increased tibial anterior shear forces and patellar tendon forces would increase ACL loading when the knee is kept at a constantly small angle. In addition, a high patellar tendon force could be generated by preparatory quadriceps activation to load the ACL even when the lower extremity was not in contact with the ground during athletic tasks. Furthermore, while exercise modalities might affect peak ACL loading, the relationship between exercise intensities and ACL loading was complex and should not be assumed to be linear.
Berns GS, Hull ML, Patterson HA. Strain in the anteromedial bundle of the anterior cruciate ligament under combination loading. J Orthop Res. 1992;10(2):167–76. https://doi.org/10.1002/jor.1100100203.
Beynnon B, Howe JG, Pope MH, Johnson RJ, Fleming BC. The measurement of anterior cruciate ligament strain in vivo. Int Orthop. 1992;16(1):1–12. https://doi.org/10.1007/BF00182976.
Beynnon BD, Fleming BC, Johnson RJ, Nichols CE, Renstrom PA, Pope MH. Anterior cruciate ligament strain behavior during rehabilitation exercises in vivo. Am J Sports Med. 1995;23(1):24–34. https://doi.org/10.1177/036354659502300105.
Beynnon BD, Johnson RJ, Fleming BC, Stankewich CJ, Renstrom PA, Nichols CE. The strain behavior of the anterior cruciate ligament during squatting and active flexion-extension. A comparison of an open and a closed kinetic chain exercise. Am J Sports Med. 1997;25(6):823–9. https://doi.org/10.1177/036354659702500616.
Bey MJ, Derwin KA. Measurement of in vivo tendon function. J Shoulder Elbow Surg. 2012;21(2):149–57. https://doi.org/10.1016/j.jse.2011.10.023.
Bates NA, Schilaty ND, Nagelli CV, Krych AJ, Hewett TE. Multiplanar Loading of the knee and its influence on anterior cruciate ligament and medial collateral ligament strain during simulated landings and noncontact tears. Am J Sports Med. 2019;47(8):1844–53. https://doi.org/10.1177/0363546519850165.
Barber-Westin S, Noyes FR. One in 5 athletes sustain Reinjury upon Return to High-Risk Sports after ACL Reconstruction: a systematic review in 1239 athletes younger than 20 years. Sports Health. 2020;12(6):587–97. https://doi.org/10.1177/1941738120912846.
Cerulli G, Benoit DL, Lamontagne M, Caraffa A, Liti A. In vivo anterior cruciate ligament strain behaviour during a rapid deceleration movement: case report. Knee Surg Sports Traumatol Arthrosc. 2003;11(5):307–11. https://doi.org/10.1007/s00167-003-0403-6.
Draganich LF, Vahey JW. An in vitro study of anterior cruciate ligament strain induced by quadriceps and hamstrings forces. J Orthop Res. 1990;8(1):57–63. https://doi.org/10.1002/jor.1100080107.
Dai B, Herman D, Liu H, Garrett WE, Yu B. Prevention of ACL injury, part Ⅰ: injury characteristics, risk factors, and loading mechanism. Res Sports Med. 2012;20(3–4):180–97. https://doi.org/10.1080/15438627.2012.680990.
Englander ZA, Martin JT, Ganapathy PK, Garrett WE, DeFrate LE. Automatic registration of MRI-based joint models to high-speed biplanar radiographs for precise quantification of in vivo anterior cruciate ligament deformation during gait. J Biomech. 2018;81:36–44. https://doi.org/10.1016/j.jbiomech.2018.09.010.
Englander ZA, Cutcliffe HC, Utturkar GM, Taylor KA, Spritzer CE, Garrett WE, DeFrate LE. In vivo assessment of the interaction of patellar tendon tibial shaft angle and anterior cruciate ligament elongation during flexion. J Biomech. 2019;90:123–7. https://doi.org/10.1016/j.jbiomech.2019.04.034.
Englander ZA, Baldwin EL, Smith WAR, Garrett WE, Spritzer CE, DeFrate LE. In vivo anterior cruciate ligament deformation during a single-legged Jump measured by magnetic resonance imaging and high-speed biplanar radiography. Am J Sports Med. 2019;47(13):3166–72. https://doi.org/10.1177/0363546519876074.
Englander ZA, Garrett WE, Spritzer CE, DeFrate LE. In vivo attachment site to attachment site length and strain of the ACL and its bundles during the full gait cycle measured by MRI and high-speed biplanar radiography. J Biomech. 2020;98:109443. https://doi.org/10.1016/j.jbiomech.2019.109443.
Englander ZA, Wittstein JR, Goode AP, Garrett WE, DeFrate LE. Reconsidering reciprocal length patterns of the Anteromedial and Posterolateral Bundles of the Anterior Cruciate Ligament during in vivo gait. Am J Sports Med. 2020;48(8):1893–9. https://doi.org/10.1177/0363546520924168.
Englander ZA, Lau BC, Wittstein JR, Goode AP, DeFrate LE. Patellar tendon orientation and strain are predictors of ACL strain in vivo during a Single-Leg Jump. Orthop J Sports Med. 2021;9(3):2325967121991054. https://doi.org/10.1177/2325967121991054.
Fleming BC, Beynnon BD, Nichols CE, Johnson RJ, Pope MH. An in vivo comparison of anterior tibial translation and strain in the anteromedial band of the anterior cruciate ligament. J Biomech. 1993;26(1):51–8. https://doi.org/10.1016/0021-9290(93)90612-I.
Fleming BC, Beynnon BD, Renstrom PA, Peura GD, Nichols CE, Johnson RJ. The strain behavior of the anterior cruciate ligament during bicycling. An in vivo study. Am J Sports Med. 1998;26(1):109–18. https://doi.org/10.1177/03635465980260010301.
Fleming BC, Beynnon BD, Renstrom PA, Johnson RJ, Nichols CE, Peura GD, Uh BS. The strain behavior of the anterior cruciate ligament during stair climbing: an in vivo study. Arthroscopy. 1999;15(2):185–91. https://doi.org/10.1053/ar.1999.v15.015018.
Fleming BC, Renstrom PA, Beynnon BD, Engstrom B, Peura GD, Badger GJ, Johnson RJ. The effect of weightbearing and external loading on anterior cruciate ligament strain. J Biomech. 2001;34(2):163–70. https://doi.org/10.1016/S0021-9290(00)00154-8.
Fleming BC, Renstrom PA, Ohlen G, Johnson RJ, Peura GD, Beynnon BD, Badger GJ. The gastrocnemius muscle is an antagonist of the anterior cruciate ligament. J Orthop Res. 2001;19(6):1178–84. https://doi.org/10.1016/S0736-0266(01)00057-2.
Fleming BC, Beynnon BD. In vivo measurement of ligament/tendon strains and forces: a review. Ann Biomed Eng. 2004;32(3):318–28. https://doi.org/10.1023/b:abme.0000017542.75080.86.
Flanagan SP, Salem GJ. Lower extremity joint kinetic responses to external resistance variations. J Appl Biomech. 2008;24(1):58–68. https://doi.org/10.1123/jab.24.1.58.
Gorsic M, Rochelle LE, Layer JS, Smith DT, Novak D, Dai B. Biomechanical comparisons of back and front squats with a straight bar and four squats with a transformer bar. Sports Biomech. 2020;1–16. https://doi.org/10.1080/14763141.2020.1832563.
Howe JG, Wertheimer C, Johnson RJ, Nichols CE, Pope MH, Beynnon B. Arthroscopic strain gauge measurement of the normal anterior cruciate ligament. Arthroscopy. 1990;6(3):198–204. https://doi.org/10.1016/0749-8063(90)90075-O.
Heijne A, Fleming BC, Renstrom PA, Peura GD, Beynnon BD, Werner S. Strain on the anterior cruciate ligament during closed kinetic chain exercises. Med Sci Sports Exerc. 2004;36(6):935–41. https://doi.org/10.1249/01.mss.0000128185.55587.a3.
Hosseini A, Gill TJ, Li G. In vivo anterior cruciate ligament elongation in response to axial tibial loads. J Orthop Sci. 2009;14(3):298–306. https://doi.org/10.1007/s00776-009-1325-z.
Jordan SS, DeFrate LE, Nha KW, Papannagari R, Gill TJ, Li G. The in vivo kinematics of the anteromedial and posterolateral bundles of the anterior cruciate ligament during weightbearing knee flexion. Am J Sports Med. 2007;35(4):547–54. https://doi.org/10.1177/0363546506295941.
Kanamori A, Woo SL, Ma CB, Zeminski J, Rudy TW, Li G, Livesay GA . The forces in the anterior cruciate ligament and knee kinematics during a simulated pivot shift test: a human cadaveric study using robotic technology. Arthroscopy. 2000;16(6):633–9. https://doi.org/10.1053/jars.2000.7682.
Kamath GV, Murphy T, Creighton RA, Viradia N, Taft TN, Spang JT. Anterior cruciate ligament Injury, Return to play, and Reinjury in the Elite Collegiate Athlete: analysis of an NCAA Division I cohort. Am J Sports Med. 2014;42(7):1638–43. https://doi.org/10.1177/0363546514524164.
Kiapour AM, Demetropoulos CK, Kiapour A, Quatman CE, Wordeman SC, Goel VK, Hewett TE. Strain response of the anterior cruciate ligament to Uniplanar and Multiplanar loads during simulated landings: implications for Injury mechanism. Am J Sports Med. 2016;44(8):2087–96. https://doi.org/10.1177/0363546516640499.
Kay MC, Register-Mihalik JK, Gray AD, Djoko A, Dompier TP, Kerr ZY. The epidemiology of severe Injuries sustained by National Collegiate Athletic Association student-athletes, 2009–2010 through 2014–2015. J Athl Train. 2017;52(2):117–28. https://doi.org/10.4085/1062-6050-52.1.01.
Li G, DeFrate LE, Sun H, Gill TJ. In vivo elongation of the anterior cruciate ligament and posterior cruciate ligament during knee flexion. Am J Sports Med. 2004;32(6):1415–20. https://doi.org/10.1177/0363546503262175.
Li G, Defrate LE, Rubash HE, Gill TJ. In vivo kinematics of the ACL during weight-bearing knee flexion. J Orthop Res. 2005;23(2):340–4. https://doi.org/10.1016/j.orthres.2004.08.006.
Lohmander LS, Englund PM, Dahl LL, Roos EM. The long-term consequence of anterior cruciate ligament and meniscus injuries: osteoarthritis. Am J Sports Med. 2007;35(10):1756–69. https://doi.org/10.1177/0363546507307396.
Lyman S, Koulouvaris P, Sherman S, Do H, Mandl LA, Marx RG. Epidemiology of anterior cruciate ligament reconstruction: trends, readmissions, and subsequent knee surgery. J Bone Joint Surg Am. 2009;91(10):2321–8. https://doi.org/10.2106/JBJS.H.00539.
Laughlin WA, Weinhandl JT, Kernozek TW, Cobb SC, Keenan KG, O’Connor KM. The effects of single-leg landing technique on ACL loading. J Biomech. 2011;44(10):1845–51. https://doi.org/10.1016/j.jbiomech.2011.04.010.
Luque-Seron JA, Medina-Porqueres I. Anterior cruciate ligament strain in vivo: a systematic review. Sports Health. 2016;8(5):451–5. https://doi.org/10.1177/1941738116658006.
Majewski M, Susanne H, Klaus S. Epidemiology of athletic knee injuries: a 10-year study. Knee. 2006;13(3):184–8. https://doi.org/10.1016/j.knee.2006.01.005.
Mather RC, Koenig L, Kocher MS, Dall TM, Gallo P, Scott DJ, Bach Jr BR, Spindler KP, MOON Knee Group. Societal and economic impact of anterior cruciate ligament tears. J Bone Joint Surg Am. 2013;95(19):1751–9. https://doi.org/10.2106/JBJS.L.01705.
Nagai K, Gale T, Chiba D, Su F, Fu F, Anderst W. The complex relationship between in vivo ACL elongation and knee kinematics during walking and running. J Orthop Res 2019;37(9):1920–8. https://doi.org/10.1002/jor.24330.
Ravary B, Pourcelot P, Bortolussi C, Konieczka S, Crevier-Denoix N. Strain and force transducers used in human and veterinary tendon and ligament biomechanical studies. Clin Biomech (Bristol Avon). 2004;19(5):433–47. https://doi.org/10.1016/j.clinbiomech.2004.01.008.
Roriz P, Carvalho L, Frazao O, Santos JL, Simoes JA. From conventional sensors to fibre optic sensors for strain and force measurements in biomechanics applications: a review. J Biomech. 2014;47(6):1251–61. https://doi.org/10.1016/j.jbiomech.2014.01.054.
Rao Z, Zhou C, Kernkamp WA, Foster TE, Bedair HS, Li G. In vivo kinematics and ligamentous function of the knee during weight-bearing flexion: an investigation on mid-range flexion of the knee. Knee Surg Sports Traumatol Arthrosc. 2020;28(3):797–805. https://doi.org/10.1007/s00167-019-05499-y.
Shelburne KB, Torry MR, Pandy MG. Muscle, ligament, and joint-contact forces at the knee during walking. Med Sci Sports Exerc. 2005;37(11):1948–56. https://doi.org/10.1249/01.mss.0000180404.86078.ff.
Song Y, Li L, Hughes G, Dai B. Trunk motion and anterior cruciate ligament injuries: a narrative review of injury videos and controlled jump-landing and cutting tasks. Sports Biomech. 2021;1–19. https://doi.org/10.1080/14763141.2021.1877337.
Taylor KA, Terry ME, Utturkar GM, Spritzer CE, Queen RM, Irribarra LA, Garrett WE, DeFrate LE. Measurement of in vivo anterior cruciate ligament strain during dynamic jump landing. J Biomech. 2011;44(3):365–71. https://doi.org/10.1016/j.jbiomech.2010.10.028.
Taylor KA, Cutcliffe HC, Queen RM, Utturkar GM, Spritzer CE, Garrett WE, DeFrate LE. In vivo measurement of ACL length and relative strain during walking. J Biomech. 2013;46(3):478–83. https://doi.org/10.1016/j.jbiomech.2012.10.031.
Utturkar GM, Irribarra LA, Taylor KA, Spritzer CE, Taylor DC, Garrett WE, Defrate LE. The effects of a valgus collapse knee position on in vivo ACL elongation. Ann Biomed Eng. 2013;41(3):123–30. https://doi.org/10.1007/s10439-012-0629-x.
Wu JL, Hosseini A, Kozanek M, Gadikota HR, Gill TJ, Li G. Kinematics of the anterior cruciate ligament during gait. Am J Sports Med. 2010;38(7):1475–82. https://doi.org/10.1177/0363546510364240.
Wiggins AJ, Grandhi RK, Schneider DK, Stanfield D, Webster KE, Myer GD. Risk of secondary Injury in younger athletes after Anterior Cruciate Ligament Reconstruction: a systematic review and Meta-analysis. Am J Sports Med. 2016;44(7):1861–76. https://doi.org/10.1177/0363546515621554.
Yu B, Garrett WE. Mechanisms of non-contact ACL injuries. Br J Sports Med. 2007;41(Suppl 1):i47–51. https://doi.org/10.1136/bjsm.2007.037192.
Zhang Q, Adam NC, Hosseini Nasab SH, Taylor WR, Smith CR. Techniques for in vivo measurement of ligament and Tendon strain: a review. Ann Biomed Eng. 2021;49(1):7–28. https://doi.org/10.1007/s10439-020-02635-5.