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Esther Suter, Walter Herzog, and Robert Bray

This study assessed muscle inhibition in patients with chronic anterior cruciate ligament (ACL) deficiency or ACL reconstruction. A series of protocols were tested for their effectiveness in increasing activity of the individual knee extensor muscles and decreasing muscle inhibition of the whole quadriceps group. Quadriceps muscle inhibition was measured by superimposing an electrical twitch onto the quadriceps muscle during a maximal voluntary knee extension. The level of activation of the individual knee extensor and knee flexor muscles was assessed via electromyography (EMG). Patients with ACL pathologies showed strength deficits and muscle inhibition in the knee extensors of the involved leg and the contralateral leg. Muscle inhibition was statistically significantly greater in ACL-deficient patients compared to ACL-reconstructed patients. When a knee extension was performed in combination with a hip extension, there was a significant increase, p < 0.05, in activation of the vastus medialis and vastus lateralis muscles compared to isolated knee extension. The use of an anti-shear device, designed to help stabilize the ACL-deficient knee, resulted in increased inhibition in the quadriceps muscle. Furthermore, a relatively more complete activation of the vasti compared to the rectus femoris was achieved during a fatiguing isometric contraction. Based on the results of this study, it is concluded that performing knee extension in combination with hip extension, or performing fatiguing knee extensor contractions, may be more effective in fully activating the vasti muscles than an isolated knee extensor contraction. Training interventions are needed to establish whether these exercise protocols are more effective than traditional rehabilitation approaches in decreasing muscle inhibition and achieving better functional recovery, including equal muscle strength in the injured and the contralateral leg.

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Stephanie L. Di Stasi, Erin H. Hartigan, and Lynn Snyder-Mackler

Aberrant movement strategies are characteristic of ACL-deficient athletes with recurrent knee instability (non-copers), and may instigate premature or accelerate joint degradation. Biomechanical evaluation of kinematic changes over time may elucidate noncopers’ responses to neuromuscular intervention and ACL reconstruction (ACLR). Forty noncopers were randomized into a perturbation group or a strength training only group. We evaluated the effects of perturbation training, and then gender on knee angle and tibial position during a unilateral standing task before and after ACLR. No statistically significant interactions were found. Before surgery, the strength training only group demonstrated knee angle asymmetry, but 6 months after ACLR, both groups presented with similar knee flexion between limbs. Aberrant and asymmetrical tibial position was found only in females following injury and ACLR. Neither treatment group showed distinct unilateral standing strategies following intervention; however, males and female noncopers appear to respond uniquely to physical therapy and surgery.

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Jonathon R. Staples, Kevin A. Schafer, Matthew V. Smith, John Motley, Mark Halstead, Andrew Blackman, Amanda Haas, Karen Steger-May, Matthew J. Matava, Rick W. Wright, and Robert H. Brophy

Context: Patients with anterior cruciate ligament (ACL) tears are likely to have deficient dynamic postural stability compared with healthy sex- and age-matched controls. Objectives: To test the hypothesis that patients undergoing ACL reconstruction have decreased dynamic postural stability compared with matched healthy controls. Design: Prospective case-control study. Setting: Orthopedic sports medicine and physical therapy clinics. Patients or Other Participants: Patients aged 20 years and younger with an ACL tear scheduled for reconstruction were enrolled prospectively. Controls were recruited from local high schools and colleges via flyers. Interventions: Patients underwent double-stance dynamic postural stability testing prior to surgery, recording time to failure and dynamic motion analysis (DMA) scores. Patients were then matched with healthy controls. Main Outcome Measures: Demographics, time to failure, and DMA scores were compared between groups. Results: A total of 19 females and 12 males with ACL tears were matched with controls. Individuals with ACL tears were more active (Marx activity score: 15.7 [1.0] vs 10.8 [4.9], P < .001); had shorter times until test failure (84.4 [15.8] vs 99.5 [14.5] s, P < .001); and had higher (worse) DMA scores (627 [147] vs 481 [132], P < .001), indicating less dynamic postural stability. Six patients with ACL deficiency (1 male and 5 females) demonstrated lower (better) DMA scores than their controls, and another 7 (4 males and 3 females) were within 20% of controls. Conclusions: Patients undergoing ACL reconstruction had worse global dynamic postural stability compared with well-matched controls. This may represent the effect of the ACL injury or preexisting deficits that contributed to the injury itself. These differences should be studied further to evaluate their relevance to ACL injury risk, rehabilitation, and return to play.

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Pass Return to Sports Criteria After ACL Reconstruction Erin H. Hartigan * Joseph Zeni Jr. * Stephanie Di Stasi * Michael J. Axe * Lynn Snyder-Mackler * 8 2012 28 4 366 373 10.1123/jab.28.4.366 Unilateral Stance Strategies of Athletes With ACL Deficiency Stephanie L. Di Stasi * Erin H

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Harsh H. Buddhadev, Daniel L. Crisafulli, David N. Suprak, and Jun G. San Juan

asymmetry in power output has been observed in individuals with unilateral anterior cruciate ligament (ACL) deficiency during cycling. When pedaling at a fixed intensity, the normal ACL-intact limb increased its output by 44% to 50% to compensate for the reduced effort by the ACL-deficient leg. 11 Similar

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Salman Nazary-Moghadam, Mahyar Salavati, Ali Esteki, Behnam Akhbari, Sohrab Keyhani, and Afsaneh Zeinalzadeh

. Determining Lyapunov exponents from a time series . Physica D Nonlinear Phenomena . 1985 ; 16 ( 3 ): 285 – 317 . doi:10.1016/0167-2789(85)90011-9 10.1016/0167-2789(85)90011-9 11. Moraiti C , Stergiou N , Ristanis S , Georgoulis AD . ACL deficiency affects stride-to-stride variability as measured

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Justin M. Stanek, Jake Parish, Richard Rainville, and Jeffrey G. Williams

.1097/00003086-200002000-00022 27. Zhang L , Dobson S , Shiavi R , Peterson S , Limbird T . Changes in knee kinematics caused by ACL deficiency during fast walking . Gait Posture . 1993 ; 7 : 144 – 156 . 28. Ness M , Long J , Marks R , Harris G . Foot and ankle kinematics in patients with posterior

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Joerg Teichmann, Rachel Tan, Kim Hébert-Losier, Yeo Wee Kian, Shabana Jalal Din, Ananthi Subramaniam, Dietmar Schmidtbleicher, and C. Martyn Beaven

given the known neuromuscular asymmetries associated with ACL deficiency. 24 Another important aspect of injury rehabilitation is overcoming the fear of movements that could cause reinjury, known as kinesiophobia. Kinesiophobia has been closely correlated with the lack of or failure to return to sport

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Jonathan Sinclair and Paul J. Taylor

knee motion during their sports-specific movements. The majority of the research investigating the efficacy of knee bracing in relation to the ACL has examined its effects in those with preexisting pathologies, either in those with ACL deficiencies or following ACL reconstruction. 14 – 17 There is

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Komeil Dashti Rostami, Aynollah Naderi, and Abbey Thomas

muscle activation in chronic ACL deficiency . Knee Surg Sports Traumatol Arthrosc . 2010 ; 18 ( 1 ): 106 – 114 . PubMed ID: 19693489 doi:10.1007/s00167-009-0886-x 19693489 10.1007/s00167-009-0886-x 17. Klyne DM , Keays SL , Bullock-Saxton JE , Newcombe PA . The effect of anterior cruciate