Document Type : Original Articles


1 Department of Health and Sports Medicine, Faculty of Physical Education and Sports Sciences, University of Tehran, Tehran

2 Department of Sport Biomechanics and Technology, Sport Science Research Institute, Tehran, Iran.


Background: Knee valgus angle seems to be a key factor in both primary– and second–ACL injury risk models. The control of the alignment of the lower limb during dynamic movements depends on the neural activation of the muscles crossing the knee joint prior to the occurrence of stressful events. The current study examined the relationship between the preparatory knee muscle activity and knee valgus angle.
Methods: Twenty-eight ACL reconstructed (ACLR) athletes were asked to perform three trials of a single-leg cross drop landing (SCD). Lower extremity kinematics and surface EMG were recorded. Initial contact knee valgus angle and EMG from 100 ms prior to ground contact were used in the data analyses.
Results: Preparatory activation medial and lateral hamstring muscles were found to be negatively correlated with knee valgus angle at initial contact (P < 0.05). However, the preparatory activity of vastus medialis and vastus lateralis muscles was not associated with initial contact knee valgus angle (P > 0.05).
Conclusions: The preparatory activity of the knee muscles is linked to knee valgus angle at initial contact, and it may indicate a potential target of second ACL injury prevention programs.


1.            Mall NA, Chalmers PN, Moric M, Tanaka MJ, Cole BJ, Bach BR, et al. Incidence and Trends of Anterior Cruciate Ligament Reconstruction in the United States. The American Journal of Sports Medicine. 2014;42(10):2363-70.
2.            Hewett TE, Di Stasi SL, Myer GD. Current concepts for injury prevention in athletes after anterior cruciate ligament reconstruction. The American journal of sports medicine. 2013;41(1):216-24.
3.            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. The American journal of sports medicine. 2016;44(7):1861-76.
4.            Øiestad BE, Holm I, Aune AK, Gunderson R, Myklebust G, Engebretsen L, et al. Knee function and prevalence of knee osteoarthritis after anterior cruciate ligament reconstruction: a prospective study with 10 to 15 years of follow-up. The American journal of sports medicine. 2010;38(11):2201-10.
5.            Shelbourne KD, Gray T, Haro M. Incidence of subsequent injury to either knee within 5 years after anterior cruciate ligament reconstruction with patellar tendon autograft. The American journal of sports medicine. 2009;37(2):246-51.
6.            Paterno MV, Ford KR, Myer GD, Heyl R, Hewett TE. Limb asymmetries in landing and jumping 2 years following anterior cruciate ligament reconstruction. Clinical Journal of Sport Medicine. 2007;17(4):258-62.
7.            Paterno MV, Schmitt LC, Ford KR, Rauh MJ, Myer GD, Huang B, et al. Biomechanical measures during landing and postural stability predict second anterior cruciate ligament injury after anterior cruciate ligament reconstruction and return to sport. The American journal of sports medicine. 2010;38(10):1968-78.
8.            Ardern CL, Webster KE, Taylor NF, Feller JA. Return to the preinjury level of competitive sport after anterior cruciate ligament reconstruction surgery two-thirds of patients have not returned by 12 months after surgery. The American journal of sports medicine. 2011;39(3):538-43.
9.            Johnston PT, McClelland JA, Webster KE. Lower Limb Biomechanics During Single-Leg Landings Following Anterior Cruciate Ligament Reconstruction: A Systematic Review and Meta-Analysis. Sports Medicine. 2018:1-24.
10.          Hewett TE, Myer GD, Ford KR, Heidt Jr RS, Colosimo AJ, McLean SG, et al. Biomechanical measures of neuromuscular control and valgus loading of the knee predict anterior cruciate ligament injury risk in female athletes: a prospective study. The American journal of sports medicine. 2005;33(4):492-501.
11.          McLean SG, Huang X, Van Den Bogert AJ. Association between lower extremity posture at contact and peak knee valgus moment during sidestepping: implications for ACL injury. Clinical Biomechanics. 2005;20(8):863-70.
12.          Hoshiba T, Fukubayashi T. Biomechanical Adaptations in Subjects After Anterior Cruciate Ligament Reconstruction: Preventing Secondary Injury.  Sports Injuries and Prevention: Springer; 2015. p. 257-65.
13.          Gokeler A, Hof AL, Arnold MP, Dijkstra PU, Postema K, Otten E. Abnormal landing strategies after ACL reconstruction. Scandinavian journal of medicine & science in sports. 2010;20(1):e12-e9.
14.          Zazulak BT, Hewett TE, Reeves NP, Goldberg B, Cholewicki J. Deficits in neuromuscular control of the trunk predict knee injury risk. The American Journal of Sports Medicine. 2007;35(7):1123.
15.          Zazulak BT, Hewett TE, Reeves NP, Goldberg B, Cholewicki J. The effects of core proprioception on knee injury. The American Journal of Sports Medicine. 2007;35(3):368.
16.          Burke D, Dickson HG, Skuse NF. Task‐dependent changes in the responses to low‐threshold cutaneous afferent volleys in the human lower limb. The Journal of Physiology. 1991;432(1):445-58.
17.          Palmieri-Smith RM, Wojtys EM, Ashton-Miller JA. Association between preparatory muscle activation and peak valgus knee angle. Journal of Electromyography and Kinesiology. 2008;18(6):973-9.
18.          Beard DJ, Kyberd PJ, Fergusson CM, Dodd CA. Proprioception after rupture of the anterior cruciate ligament. An objective indication of the need for surgery? The Journal of bone and joint surgery British volume. 1993;75(2):311-5.
19.          Hefti E, Müller W, Jakob RP, Stäubli HU. Evaluation of knee ligament injuries with the IKDC form. Knee Surgery, Sports Traumatology, Arthroscopy. 1993;1(3-4):226-34.
20.          DiCesare CA, Bates NA, Barber Foss KD, Thomas SM, Wordeman SC, Sugimoto D, et al. Reliability of 3-Dimensional Measures of Single-Leg Cross Drop Landing Across 3 Different Institutions: Implications for Multicenter Biomechanical and Epidemiological Research on ACL Injury Prevention. Orthopaedic Journal of Sports Medicine. 2015;3(12):2325967115617905.
21.          Perotto AO. Anatomical guide for the electromyographer: the limbs and trunk: Charles C Thomas Publisher; 2011.
22.          Eils E, Behrens S, Mers O, Thorwesten L, Völker K, Rosenbaum D. Reduced plantar sensation causes a cautious walking pattern. Gait & posture. 2004;20(1):54-60.
23.          Donnelly CJ, Elliott BC, Doyle TLA, Finch CF, Dempsey AR, Lloyd DG. Changes in muscle activation following balance and technique training and a season of Australian football. Journal of science and medicine in sport. 2015;18(3):348-52.
24.          Myer GD, Ford KR, Palumbo JP, Hewett TE. Neuromuscular training improves performance and lower-extremity biomechanics in female athletes. The Journal of Strength & Conditioning Research. 2005;19(1):51-60.
25.          Zhang L-Q, Wang G. Dynamic and static control of the human knee joint in abduction–adduction. Journal of biomechanics. 2001;34(9):1107-15.
26.          Nyland J, Brand E, Fisher B. Update on rehabilitation following ACL reconstruction. Open access journal of sports medicine. 2010;1:151.
27.          Lloyd DG, Buchanan TS, Besier TF. Neuromuscular biomechanical modeling to understand knee ligament loading. Medicine and science in sports and exercise. 2005;37(11):1939-47.
28.          Goerger BM, Marshall SW, Beutler AI, Blackburn JT, Wilckens JH, Padua DA. Anterior cruciate ligament injury alters preinjury lower extremity biomechanics in the injured and uninjured leg: the JUMP-ACL study. Br J Sports Med. 2015;49(3):188-95.
29.          Nyland J, Klein S, Caborn DNM. Lower extremity compensatory neuromuscular and biomechanical adaptations 2 to 11 years after anterior cruciate ligament reconstruction. Arthroscopy: The Journal of Arthroscopic & Related Surgery. 2010;26(9):1212-25.
30.          Blackburn JT, Padua DA. Sagittal-plane trunk position, landing forces, and quadriceps electromyographic activity. Journal of athletic training. 2009;44(2):174.
31.          Nyland J, Kuzemchek S, Parks M, Caborn DNM. Femoral anteversion influences vastus medialis and gluteus medius EMG amplitude: composite hip abductor EMG amplitude ratios during isometric combined hip abduction-external rotation. Journal of electromyography and kinesiology. 2004;14(2):255-61.
32.          Coventry E, O’Connor KM, Hart BA, Earl JE, Ebersole KT. The effect of lower extremity fatigue on shock attenuation during single-leg landing. Clinical Biomechanics. 2006;21(10):1090-7.