scholarly journals Do Muscle Strength Deficits of the Uninvolved Hip and Knee Exist in Young Athletes Before Anterior Cruciate Ligament Reconstruction?

2017 ◽  
Vol 5 (1) ◽  
pp. 232596711668394 ◽  
Author(s):  
Joseph Hannon ◽  
Sharon Wang-Price ◽  
Shiho Goto ◽  
J. Craig Garrison ◽  
James M. Bothwell
Keyword(s):  
Muscle Strength ◽  
Cruciate Ligament ◽  
Acl Injury ◽  
Quadriceps Muscle ◽  
Quadriceps Strength ◽  
Control Group ◽  
Isokinetic Strength ◽  
Healthy Controls ◽  
Healthy Control ◽  
Anterior Cruciate

Background: Muscle strength of the involved limb is known to be decreased after injury. Comparison with the uninvolved limb has become standard of practice to measure progress and for calculation of limb symmetry indices (LSIs) to determine readiness to return to sport. However, some literature suggests strength changes in the uninvolved limb also are present after lower extremity injury. Purpose: To examine the uninvolved limb strength in a population of adolescent athletes after an anterior cruciate ligament (ACL) injury and compare strength values with those of the dominant limb in a healthy control group. Study Design: Cohort study; Level of evidence, 3. Methods: A total of 64 athletes were enrolled in this study, including 31with injured ACLs (mean age, 15.6 ± 1.4 years) and 33 healthy controls (mean age, 14.9 ± 1.9 years). The median time from injury to testing was 23 days for the ACL-injured group. Participants underwent Biodex isokinetic strength testing at 60 deg/s to assess quadriceps and hamstring strength. Isometric hip strength (abduction, extension, external rotation) was measured using a handheld dynamometer. The muscle strength of the uninvolved limb of the ACL-injured group was compared with that of the dominant limb of the healthy control group. Results: The results showed a significant difference in quadriceps muscle strength between the 2 study groups ( P < .001). Isokinetic quadriceps strength of the uninvolved limb in the ACL group was significantly decreased by 25.5% ( P < .001) when compared with the dominant limb of the control group. Conclusion: The results of this study demonstrate a decreased isokinetic strength of the quadriceps muscle in the uninvolved limb after ACL injury as compared with healthy controls. Consideration should be taken when using the uninvolved limb for comparison when assessing quadriceps strength in a population with an ACL injury.

scholarly journals Physiotherapy and Electrical Stimulation Effects on Strength of M. Quadriceps, Knee Range of Motion and Pain in Patients Following Anterior Cruciate Ligament Operation

2019 ◽  
Vol 1 (16) ◽  
Author(s):  
Justina Marčiulionytė ◽  
Justinas Škikas ◽  
Saulė Sipavičienė
Keyword(s):  
Anterior Cruciate Ligament ◽  
Electrical Stimulation ◽  
Muscle Strength ◽  
Range Of Motion ◽  
Cruciate Ligament ◽  
Quadriceps Muscle ◽  
Control Group ◽  
Study Group ◽  
Quadriceps Muscle Strength ◽  
Anterior Cruciate

Background. Research aim was to analyze the quadriceps muscle strength recovery after anterior cruciate ligament reconstruction using electrical stimulation and physical therapy. Methods. There were two randomly selected groups, with eight people in each group. The selection criteria were that the subjects had to have anterior cruciate ligament operation six weeks prior and were very active physically. One group was for research (study group), the other one for reference (control group). The study group had electrical stimulation combined with physical therapy exercises two times a week, for 45 minutes. The control group had exercises to strengthen the quadriceps muscle also two times a week, for 45 minutes. Both groups were tested before and after the research. The things evaluated during the test were – visual pain scale (VAS) scores, quadriceps muscle strength during extension and flexion using (R. Lovett) scoring system and goniometry showing degrees of extension and flexion. Results. Comparing both study and control groups, there was statistically signifcant improvement (p < 0.05), however the study group recovered faster and had statistically greater benefts. Conclusions. After 6 weeks of physiotherapy, the range of motion, quadriceps muscle strength increased and pain decreased in the operated leg. 1. After 6 weeks of physiotherapy and electrical stimulation, the range of motion, quadriceps muscle strength increased and pain decreased in the operated leg. 2. After 6 weeks of physiotherapy and electrical stimulation, the range of motion, quadriceps muscle strength, pain in the operated leg changed more in the study group than in subjects who received only physical therapy.Keywords: anterior cruciate ligament, electrical stimulation, quadriceps muscle, ligament reconstruction, muscle strength.

scholarly journals Michigan Initiative for Anterior Cruciate Ligament Rehabilitation (MiACLR): A Protocol for a Randomized Clinical Trial

2020 ◽  
Vol 100 (12) ◽  
pp. 2154-2164
Author(s):  
Kazandra Rodriguez ◽  
Steven A Garcia ◽  
Cathie Spino ◽  
Lindsey K Lepley ◽  
Yuxi Pang ◽  
...  
Keyword(s):  
Clinical Trial ◽  
Anterior Cruciate Ligament ◽  
Muscle Strength ◽  
Cruciate Ligament ◽  
Quadriceps Muscle ◽  
Quadriceps Strength ◽  
Neurological Deficits ◽  
Secondary Outcome ◽  
Patient Reported ◽  
Anterior Cruciate

Abstract Objective Restoring quadriceps muscle strength following anterior cruciate ligament reconstruction (ACLR) may prevent the posttraumatic osteoarthritis that affects over 50% of knees with ACLR. However, a fundamental gap exists in our understanding of how to maximize muscle strength through rehabilitation. Neurological deficits and muscle atrophy are 2 of the leading mechanisms of muscle weakness after ACLR. High-intensity neuromuscular electrical stimulation (NMES) and eccentric exercise (ECC) have been shown to independently target these mechanisms. If delivered in succession, NMES and then ECC may be able to significantly improve strength recovery. The objectives of this study were to evaluate the ability of NMES combined with ECC to restore quadriceps strength and biomechanical symmetry and maintain cartilage health at 9 and 18 months after ACLR. Methods This study is a randomized, double-blind, placebo-controlled, single-center clinical trial conducted at the University of Michigan. A total of 112 participants between the ages of 14 and 45 years and with an anterior cruciate ligament rupture will be included. Participants will be randomly assigned 1:1 to NMES combined with ECC or NMES placebo combined with ECC placebo. NMES or NMES placebo will be delivered 2 times per week for 8 weeks beginning 10 to 14 days postoperatively and will be directly followed by 8 weeks of ECC or ECC placebo delivered 2 times per week. The co-primary endpoints are change from baseline to 9 months and change from baseline to 18 months after ACLR in isokinetic quadriceps strength symmetry. Secondary outcome measures include isometric quadriceps strength, quadriceps activation, quadriceps muscle morphology (cross-sectional area), knee biomechanics (sagittal plane knee angles and moments), indexes of patient-reported function, and cartilage health (T1ρ and T2 relaxation time mapping on magnetic resonance imaging). Impact The findings from this study might identify an intervention capable of targeting the lingering quadriceps weakness after ACLR and in turn prevent deterioration in cartilage health after ACLR, thereby potentially improving function in this patient population.

Arthroscopic Imaging Treatment and Clinical Rehabilitation of Knee Sports Injuries

2021 ◽  
Vol 11 (6) ◽  
pp. 1780-1788
Author(s):  
Habaxi Kaken ◽  
Shanshan Wang ◽  
Wei Zhao ◽  
Baoerjiang Asihaer ◽  
Li Wang
Keyword(s):  
Muscle Strength ◽  
Knee Joint ◽  
Sports Injuries ◽  
Cruciate Ligament ◽  
Quadriceps Muscle ◽  
Lower Limbs ◽  
Continuous Passive Motion ◽  
Control Group ◽  
Pressure Therapy ◽  
Quick Recovery

This article studies the effects of arthroscopic imaging treatment and clinical rehabilitation of knee sports injuries. Arthroscopy was used to perform meniscus trimming and resection for 40 patients with knee sports injuries. The ages of the patients ranged from 20 to 60 years old. All patients received routine rehabilitation training such as continuous passive motion of the knee joint, biofeedback of the lower limbs, and air pressure therapy of the lower limbs. In addition, the control group was given muscle strength training, and the training began after the patients received the quadriceps muscle strength test. The removal of the joint cavity and the joint debridement has achieved satisfactory treatment results. In the experiment, the test cases were divided into two groups, and the sensor test platform was used for signal collection. Normal activities can be resumed 2 weeks after the operation. After a follow-up of 6 to 24 months, the knee joint pain disappeared, the joint was free of swelling, and the knee function was normal up to 93%. Arthroscopic reconstruction of the anterior and posterior cruciate ligament joint repair/reconstruction of the medial and posterolateral ligament knots is safe and feasible for the treatment of multiple ligament injuries of the knee joint. It has the advantages of less trauma and quick recovery. Early postoperative systemic and standardized rehabilitation exercises can obtain good knee joint function.

scholarly journals Quadriceps Activation Following Knee Injuries: A Systematic Review

2010 ◽  
Vol 45 (1) ◽  
pp. 87-97 ◽  
Author(s):  
Joseph M. Hart ◽  
Brian Pietrosimone ◽  
Jay Hertel ◽  
Christopher D. Ingersoll
Keyword(s):  
Anterior Cruciate Ligament ◽  
Knee Injury ◽  
Data Extraction ◽  
Cruciate Ligament ◽  
Knee Injuries ◽  
Quadriceps Muscle ◽  
Control Group ◽  
Data Sets ◽  
Weighted Mean ◽  
Anterior Cruciate

Abstract Context: Arthrogenic muscle inhibition is an important underlying factor in persistent quadriceps muscle weakness after knee injury or surgery. Objective: To determine the magnitude and prevalence of volitional quadriceps activation deficits after knee injury. Data Sources: Web of Science database. Study Selection: Eligible studies involved human participants and measured quadriceps activation using either twitch interpolation or burst superimposition on patients with knee injuries or surgeries such as anterior cruciate ligament deficiency (ACLd), anterior cruciate ligament reconstruction (ACLr), and anterior knee pain (AKP). Data Extraction: Means, measures of variability, and prevalence of quadriceps activation (QA) failure (&lt;95%) were recorded for experiments involving ACLd (10), ACLr (5), and AKP (3). Data Synthesis: A total of 21 data sets from 18 studies were initially identified. Data from 3 studies (1 paper reporting data for both ACLd and ACLr, 1 on AKP, and the postarthroscopy paper) were excluded from the primary analyses because only graphical data were reported. Of the remaining 17 data sets (from 15 studies), weighted mean QA in 352 ACLd patients was 87.3% on the involved side, 89.1% on the uninvolved side, and 91% in control participants. The QA failure prevalence ranged from 0% to 100%. Weighted mean QA in 99 total ACLr patients was 89.2% on the involved side, 84% on the uninvolved side, and 98.5% for the control group, with prevalence ranging from 0% to 71%. Thirty-eight patients with AKP averaged 78.6% on the involved side and 77.7% on the contralateral side. Bilateral QA failure was commonly reported in patients. Conclusions: Quadriceps activation failure is common in patients with ACLd, ACLr, and AKP and is often observed bilaterally.

Blood Flow Restriction Training Applied With High-Intensity Exercise Does Not Improve Quadriceps Muscle Function After Anterior Cruciate Ligament Reconstruction: A Randomized Controlled Trial

2020 ◽  
Vol 48 (4) ◽  
pp. 825-837 ◽  
Author(s):  
Michael T. Curran ◽  
Asheesh Bedi ◽  
Christopher L. Mendias ◽  
Edward M. Wojtys ◽  
Megan V. Kujawa ◽  
...  
Keyword(s):  
Muscle Strength ◽  
High Intensity ◽  
Muscle Function ◽  
Controlled Trial ◽  
Cruciate Ligament ◽  
Quadriceps Muscle ◽  
High Intensity Exercise ◽  
Quadriceps Muscle Strength ◽  
Flow Restriction ◽  
Anterior Cruciate

Background: A major goal of rehabilitation after anterior cruciate ligament reconstruction (ACLR) is restoring quadriceps muscle strength. Unfortunately, current rehabilitation paradigms fall short of this goal, such that substantial quadriceps muscle strength deficits can limit return to play and increase the risk of recurrent injuries. Blood flow restriction training (BFRT) involves the obstruction of venous return to working muscles during exercise and may lead to better recovery of quadriceps muscle strength after ACLR. Purpose: To examine the efficacy of BFRT with high-intensity exercise on the recovery of quadriceps muscle function in patients undergoing ACLR. Study Design: Randomized controlled trial; Level of evidence, 2. Methods: A total of 34 patients (19 female, 15 male; mean age, 16.5 ± 2.7 years; mean height, 169.0 ± 19.7 cm; mean weight, 73.2 ± 17.7 kg) scheduled to undergo ACLR were randomly assigned to 1 of 4 groups: concentric (n = 8), eccentric (n = 8), concentric with BFRT (n = 9), and eccentric with BFRT (n = 9). The exercise component of the intervention consisted of patients performing a single-leg isokinetic leg press, at an intensity of 70% of the patients’ 1-repetition maximum during either the concentric or eccentric action, for 4 sets of 10 repetitions 2 times per week for 8 weeks beginning at 10 weeks postoperatively. Patients randomized to the BFRT groups performed the leg-press exercise with a cuff applied to the thigh, set to a limb occlusion pressure of 80%. Isometric and isokinetic (60 deg/s) quadriceps peak torque, quadriceps muscle activation, and rectus femoris muscle volume were assessed before ACLR, after BFRT, and at the time that patients returned to activity and were converted to the change in values from baseline for analysis. Also, 1-way analyses of covariance were used to compare the change in values for each dependent variable between groups after BFRT and at return to activity ( P ≤ .05). Results: No significant differences were found between groups for any outcome measures at either time point ( P > .05). Conclusion: An 8-week BFRT plus high-intensity exercise intervention did not significantly improve quadriceps muscle strength, activation, or volume. On the basis of our findings, the use of BFRT in conjunction with high-intensity resistance exercise in patients undergoing ACLR to improve quadriceps muscle function may not be warranted. Registration: NCT03141801 ( ClinicalTrials.gov identifier)

scholarly journals Anterior Cruciate Ligament Injury

2014 ◽  
Vol 2 (12_suppl4) ◽  
pp. 2325967114S0025
Author(s):  
Tomas Vilaseca ◽  
Jorge Chahla ◽  
Gustavo Gomez Rodriguez ◽  
Damián Arroquy ◽  
Gonzalo Perez Herrera ◽  
...  
Keyword(s):  
Anterior Cruciate Ligament ◽  
Internal Rotation ◽  
Cruciate Ligament ◽  
Acl Injury ◽  
T Test ◽  
Control Group ◽  
Recreational Athletes ◽  
Significant Difference ◽  
Anterior Cruciate ◽  
Knee Pathology

Objectives: The objective of this study was to analyze whether it is more frequent the presence of a decreased range of motion in the hips of recreational athletes with primary injury of the anterior cruciate ligament (ACL) than in a control group of volunteers without knee pathology. Methods: We included prospectively recreational athletes between 18 and 40 years with an acute ACL injury between January 2011 and January 2013. They were compared with a control group of volunteers recreational athletes without lower limb pathology and in the same range of age. The internal and external rotations passively prior to the point at which the pelvis movement contributes were observed. The results were statistically analyzed using t test for related samples to the hips of patients with ACL injury and t test for independent variables for comparison with the control group. Results: 48 patients with ACL injury and 53 healthy volunteers were evaluated. The ACL group was composed of 32 males and 16 females with an average age of 29.3 years. In the control group 26 males and 27 females were studied with a mean age of 26.6 years. Internal (IR) and external (ER) rotation in the LCA group was 22,9º and 55,5º respectively in the ipsilateral hip and 27,9º and 57,7º in the contralateral. In the control group a 35,9º of IR and 55,2º of ER was observed. The analysis showed an association between ACL injury and hypomotility of the hip further expense of a decrease in internal rotation. The analysis showed an association between ACL injury and hypomotility of the hip at the expense to a greater decrease in internal rotation. Conclusion: We found a statistically significant difference in the mobility of the hips in patients with ACL injury predominantly due to internal rotation, pattern that allows us to interpret this injury not only as an intrinsic etiology of the knee but also of the adjacent joints. We consider very importance to incorporate prevention activities and screening of risk factors regarding to at least high performance athletes.

scholarly journals Does Anterior Cruciate Ligament Reconstruction Improve Functional and Radiographic Outcomes Over Nonoperative Management 5 Years After Injury?

2018 ◽  
Vol 46 (9) ◽  
pp. 2103-2112 ◽  
Author(s):  
Elizabeth Wellsandt ◽  
Matthew J. Failla ◽  
Michael J. Axe ◽  
Lynn Snyder-Mackler
Keyword(s):  
Nonoperative Management ◽  
Cruciate Ligament ◽  
Acl Injury ◽  
Quadriceps Strength ◽  
Nonoperative Treatment ◽  
Joint Effusion ◽  
Long Term Outcomes ◽  
Radiographic Outcomes ◽  
Anterior Cruciate

Background: Current practice patterns for the management of anterior cruciate ligament (ACL) injury favor surgical reconstruction. However, long-term outcomes may not differ between patients completing operative and nonoperative treatment of ACL injury. Differences in outcomes between operative and nonoperative treatment of patients in the United States is largely unknown, as are outcomes in long-term strength and performance measures. Purpose: To determine if differences exist in 5-year functional and radiographic outcomes between patients completing operative and nonoperative treatment of ACL injury when both groups complete a progressive criterion-based rehabilitation protocol. Study Design: Cohort study; Level of evidence, 2. Methods: From an original group of 144 athletes, 105 participants (mean ± SD age, 34.3 ± 11.4 years) with an acute ACL rupture completed functional testing (quadriceps strength, single-legged hop, and knee joint effusion testing; patient-reported outcomes) and knee radiographs 5 years after ACL reconstruction or completion of nonoperative rehabilitation. Results: At 5 years, patients treated with ACL reconstruction versus rehabilitation alone did not differ in quadriceps strength ( P = .817); performance on single-legged hop tests ( P = .234-.955); activity level ( P = .349-.400); subjective reports of pain, symptoms, activities of daily living, and knee-related quality of life ( P = .090-.941); or presence of knee osteoarthritis ( P = .102-.978). When compared with patients treated nonoperatively, patients treated operatively did report greater global ratings of knee function ( P = .001), and lower fear ( P = .035) at 5 years but were more likely to possess knee joint effusion ( P = .016). Conclusion: The current findings indicate that favorable outcomes can occur after both operative and nonoperative management approaches with the use of progressive criterion-based rehabilitation. Further study is needed to determine clinical algorithms for identifying the best candidates for surgical versus nonoperative care after ACL injury. These findings provide an opportunity to improve the educational process between patients and clinicians regarding the expected clinical course and long-term outcomes of operative and nonoperative treatment of ACL injuries.

scholarly journals The Effect of External Focus Attention Exercise On the Kinetic Risk Factors Associated With ACL Injury

2021 ◽  
Vol 10 (3) ◽  
pp. 470-485
Author(s):  
Nazanin Dalvandpour ◽  
◽  
Mostafa Zarei ◽  
Behrouz Abdoli ◽  
Hamed Abbasi ◽  
...  
Keyword(s):  
Injury Prevention ◽  
Ground Reaction Force ◽  
Cruciate Ligament ◽  
Reaction Force ◽  
Acl Injury ◽  
Control Group ◽  
External Focus ◽  
Time To Stabilization ◽  
Internal Focus ◽  
Anterior Cruciate

Background and Aims One of the most common and dangerous injuries in sports is an Anterior Cruciate Ligament (ACL) injury. Today, despite the ACL injury prevention programs, the prevalence of this injury remains high. Most of the instructions used in injury prevention programs are based on internal focus, while studies have shown that using external focus can improve performance in individuals. The purpose of this study was to investigate the effect of focus of attention on eight weeks of anterior cruciate ligament injury prevention training on landing skill kinetic variables in soccer players. Methods The current methodology included 35 players from 3 premier league teams in Tehran province. The teams were randomly divided into three groups of Prevent injury and Enhance Performance (PEP) exercises based on the External Focus (EF) (12 people), Internal Focus (IF) (12 people), and control group (11 people). In the pretest of ground reaction force, rate of loading, and time to stabilization during landing skill. The training groups performed pep injury prevention exercises for eight weeks and related instructions instead of warm-up exercises. Control group players were performing the regular activities. ANOVA with repeated measures and one-way ANOVA and Tukey post hoc tests were used to evaluate changes Results The test results showed significant changes in vertical, anterior-posterior ground reaction force and rate of loading in the external focus group (P≤0.05). But there was no critical difference in time to stabilization and internal-external ground reaction force. Conclusion According to the results, external focus instruction has positive effects on kinetic components. Therefore, it is recommended that exercises based on these instructions be used to reduce the risk of ACL injury and to repair this injury.

scholarly journals Increased Lateral and Medial Femoral Posterior Radius Ratios Are Risk Factors for Anterior Cruciate Ligament Injury

2021 ◽  
Author(s):  
Chunxu Fu ◽  
Xuguo Fan ◽  
Shigang Jiang ◽  
Junsen Wang ◽  
Tong Li ◽  
...  
Keyword(s):  
Risk Factors ◽  
Distal Femur ◽  
Cruciate Ligament ◽  
Morphological Characteristics ◽  
Acl Injury ◽  
Curve Analysis ◽  
Control Group ◽  
Roc Curve Analysis ◽  
Injury Group ◽  
Anterior Cruciate

Abstract Background Many studies have shown that the distal femoral sagittal morphological characteristics had a clear relationship with knee joint kinematics. The aim of this study was to determine the relationship between distal femoral sagittal morphological characteristics and noncontact anterior cruciate ligament (ACL) injury. Methods A retrospective case-control study of 148 patients was conducted. Two age- and sex-matched cohorts (each n = 74) were analysed: a noncontact ACL injury group and a control group. The lateral femoral posterior radius (LFPR), medial femoral posterior radius (MFPR), lateral height of the distal femur (LH), medial height of the distal femur (MH), lateral femoral anteroposterior diameter (LFAP), medial femoral anteroposterior diameter (MFAP), lateral femoral posterior radius ratio (LFPRR), and medial femoral posterior radius ratio (MFPRR) were compared between the two groups. Receiver operating characteristic (ROC) curve analysis was used to evaluate the significance of the LFPRR and MFPRR in predicting ACL injury. Results Compared with patients in the control group, patients in the ACL injury group had an increased LFPR, MFPR, MFAP, LFPRR, and MFPRR. ROC curve analysis revealed that an increased LFPRR above 31.7% was associated with noncontact ACL injury, with a sensitivity of 78.4% and a specificity of 58.1%, and an increased MFPRR above 33.4% was associated with noncontact ACL injury, with a sensitivity of 58.1% and a specificity of 70.3%. Conclusion This study showed that increased LFPRR and MFPRR were risk factors for noncontact ACL injury. These data could help identify individuals susceptible to ACL injuries.

scholarly journals Anterior Cruciate Ligament Tear Promotes Skeletal Muscle Myostatin Expression, Fibrogenic Cell Expansion, and a Decline in Muscle Quality

2019 ◽  
Vol 47 (6) ◽  
pp. 1385-1395 ◽  
Author(s):  
Bailey D. Peck ◽  
Camille R. Brightwell ◽  
Darren L. Johnson ◽  
Mary Lloyd Ireland ◽  
Brian Noehren ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Extracellular Matrix ◽  
Anterior Cruciate Ligament ◽  
Cruciate Ligament ◽  
Acl Injury ◽  
Quadriceps Muscle ◽  
Muscle Quality ◽  
Injured Limb ◽  
Extracellular Matrix Components ◽  
Anterior Cruciate

Background: Anterior cruciate ligament (ACL) tears result in significant quadriceps muscle atrophy that is resistant to recovery despite extensive rehabilitation. Recent work suggests an elevated fibrotic burden in the quadriceps muscle after the injury, which may limit recovery. Elucidating the mechanisms and cell types involved in the progression of fibrosis is critical for developing new treatment strategies. Purpose: To identify factors contributing to the elevated fibrotic burden found after the injury. Study Design: Descriptive laboratory study. Methods: After an ACL injury, muscle biopsy specimens were obtained from the injured and noninjured vastus lateralis of young adults (n = 14, mean ± SD: 23 ± 4 years). The expression of myostatin, transforming growth factor β, and other regulatory factors was measured, and immunohistochemical analyses were performed to assess turnover of extracellular matrix components. Results: Injured limb skeletal muscle demonstrated elevated myostatin gene ( P < .005) and protein ( P < .0005) expression, which correlated ( R2 = 0.38, P < .05) with fibroblast cell abundance. Immunohistochemical analysis showed that human fibroblasts express the activin type IIB receptor and that isolated primary human muscle-derived fibroblasts increased proliferation after myostatin treatment in vitro ( P < .05). Collagen 1 and fibronectin, primary components of the muscle extracellular matrix, were significantly higher in the injured limb ( P < .05). The abundance of procollagen 1–expressing cells as well as a novel index of collagen remodeling was also elevated in the injured limb ( P < .05). Conclusion: These findings support a role for myostatin in promoting fibrogenic alterations within skeletal muscle after an ACL injury. Clinical Relevance: The current work shows that the cause of muscle quality decline after ACL injury likely involves elevated myostatin expression, and future studies should explore therapeutic inhibition of myostatin to facilitate improvements in muscle recovery and return to sport.

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