Search

The purpose of this study was to identify alterations in preparatory muscle activation patterns across different drop heights in female athletes. Sixteen female high school volleyball players performed the drop vertical jump from three different drop heights. Surface electromyography of the quadriceps and hamstrings were collected during the movement trials. As the drop height increased, muscle activation of the quadriceps during preparatory phase also increased (p < .05). However, the hamstrings activation showed no similar increases relative to drop height. Female athletes appear to preferentially rely on increased quadriceps activation, without an increase in hamstrings activation, with increased plyometric intensity. The resultant decreased activation ratio of the hamstrings relative to quadriceps before landing may represent altered dynamic knee stability and may contribute to the increased risk of ACL injury in female athletes.

Following the onset of maturation, female athletes have a significantly higher risk for anterior cruciate ligament (ACL) injury compared with male athletes. While multiple sex differences in lower-extremity neuromuscular control and biomechanics have been identified as potential risk factors for ACL injury in females, the majority of these studies have focused specifically on the knee joint. However, increasing evidence in the literature indicates that lumbo-pelvic (core) control may have a large effect on knee-joint control and injury risk. This review examines the published evidence on the contributions of the trunk and hip to knee-joint control. Specifically, the sex differences in potential proximal controllers of the knee as risk factors for ACL injury are identified and discussed. Sex differences in trunk and hip biomechanics have been identified in all planes of motion (sagittal, coronal and transverse). Essentially, female athletes show greater lateral trunk displacement, altered trunk and hip flexion angles, greater ranges of trunk motion, and increased hip adduction and internal rotation during sport manoeuvres, compared with their male counterparts. These differences may increase the risk of ACL injury among female athletes. Prevention programmes targeted towards trunk and hip neuromuscular control may decrease the risk for ACL injuries.

Regular participation in organized youth sports does not ensure adequate exposure to skill- and health-related fitness activities, and sport training without preparatory conditioning does not appear to reduce risk of injury in young athletes. Current trends indicate that widespread participation in organized youth sports is occurring at a younger age, especially in girls. Current public health recommendations developed to promote muscle strengthening and bone building activities for youth aged 6 yr and older, along with increased involvement in competitive sport activities at younger ages, has increased interest and concern from parents, clinicians, coaches, and teachers regarding the optimal age to encourage and integrate more specialized physical training into youth development programs. This review synthesizes the latest literature and expert opinion regarding when to initiate neuromuscular conditioning in youth and presents a how-to integrative training conceptual model that could maximize the potential health-related benefits for children by reducing sports-related injury risk and encouraging lifelong, regular physical activity.

Objective To establish the clinical relevance of proprioceptive deficits reported after anterior cruciate ligament (ACL) injury. Material and methods A literature search was done in electronic databases from January 1990 to June 2009. Inclusion criteria for studies were ACL deficient (ACL-D) and ACL reconstruction (ACL-R) articles written in English, Dutch or German and calculation of correlation(s) between proprioception tests and clinical outcome measures. Clinical outcome measures were muscle strength, laxity, hop test, balance, patient-reported outcome, objective knee score rating, patient satisfaction or return to sports. Studies included in the review were assessed on their methodological quality. Results In total 1161 studies were identified of which 24 met the inclusion criteria. Pooling of all data was not possible due to substantial differences in measurement techniques and data analysis. Most studies failed to perform reliability measurements of the test device used. In general, the correlation between proprioception and laxity, balance, hop tests and patient outcome was low. Four studies reported a moderate correlation between proprioception, strength, balance or hop test. Conclusion There is limited evidence that proprioceptive deficits as detected by commonly used tests adversely affect function in ACL-D and ACL-R patients. Development of new tests to determine the relevant role of the sensorimotor system is needed. These tests should ideally be used as screening tests for primary and secondary prevention of ACL injury.

Stability at the knee joint is provided by both the static structures, including the ligaments and joint capsule and the coordinated activation of dynamic structures surrounding the joint. These dual stabilizers allow for functional movements, such as gait, to occur safely, effectively, and efficiently. In the presence of a multi-ligament knee injury (MLKI) an absence of static stability can result in an increased reliance on the dynamic knee stabilizers. If sufficient stability is not provided, the potential for an increase in abnormal movements in the knee joint can result. These potential gait alterations that may be associated with a MLKI can result in abnormally high stresses on healing tissues and potentially high shearing forces on articular cartilage, resulting in early breakdown. Early recognition of gait abnormalities and an appropriate implementation of a gait re-training program to control abnormal forces in a patient following an MLKI or a surgical intervention for a MLKI are critical for successful long-term outcomes.

Background Bone bruises located on the lateral femoral condyle and posterolateral tibia are commonly associated with anterior cruciate ligament (ACL) injuries and may contribute to the high risk for knee osteoarthritis after ACL injury. The resultant footprint (location) of a bone bruise after ACL injury provides evidence of the inciting injury mechanism. Purpose/Hypothesis ( 1 ) To analyze tibial and femoral articular cartilage pressure distributions during normal landing and injury simulations, and ( 2 ) to evaluate ACL strains for conditions that lead to articular cartilage pressure distributions similar to bone bruise patterns associated with ACL injury. The hypothesis was that combined knee abduction and anterior tibial translation injury simulations would demonstrate peak articular cartilage pressure distributions in the lateral femoral condyle and posterolateral tibia. The corollary hypothesis was that combined knee abduction and anterior tibial translation injury conditions would result in the highest ACL strains. Study Design Descriptive laboratory study. Methods Prospective biomechanical data from athletes who subsequently suffered ACL injuries after testing (n = 9) and uninjured teammates (n = 390) were used as baseline input data for finite element model comparisons. Results Peak articular pressures that occurred on the posterolateral tibia and lateral femoral condyle were demonstrated for injury conditions that had a baseline knee abduction angle of 5°. Combined planar injury conditions of abduction/anterior tibial translation, anterior tibial translation/internal tibial rotation, or anterior tibial translation/external tibial rotation or isolated anterior tibial translation, external tibial rotation, or internal tibial rotation resulted in peak pressures in the posterolateral tibia and lateral femur. The highest ACL strains occurred during the combined abduction/anterior tibial translation condition in the group that had a baseline knee abduction angle of 5°. Conclusion The results of this study support a valgus collapse as the major ACL injury mechanism that results from tibial abduction rotations combined with anterior tibial translation or external or internal tibial rotations. Clinical Relevance Reduction of large multiplanar knee motions that include abduction, anterior translation, and internal/external tibial motions may reduce the risk for ACL injuries and associated bone bruises. In particular, prevention of an abduction knee posture during initial contact of the foot with the ground may help prevent ACL injury.

AIMS: Prospective measures of high knee abduction moment (KAM) during landing identify female athletes at increased risk for anterior cruciate ligament (ACL) injury. Laboratory-driven measurements predict high KAM with 90% accuracy. This study aimed to validate the clinic-based variables against 3-dimensional motion analysis measurements. METHODS: Twenty female basketball, soccer, and volleyball players (age, 15.9 ± 1.3 years; height, 163.6 ± 9.9 cm; body mass, 57.0 ± 12.1 kg) were tested using 3-dimensional motion analysis and clinic-based techniques simultaneously. Multiple logistic regression models have been developed to predict high KAM (a surrogate for ACL injury risk) using both measurement techniques. Clinic-based measurements were validated against 3-dimensional motion analysis measures, which were recorded simultaneously, using within- and between-method reliability as well as sensitivity and specificity comparisons. RESULTS: The within-variable analysis showed excellent inter-rater reliability for all variables using both 3-dimensional motion analysis and clinic-based methods, with intraclass correlation coefficients (ICCs) that ranged from moderate to high (0.60–0.97). In addition, moderate-to-high agreement was observed between 3-dimensional motion analysis and clinic-based measures, with ICCs ranging from 0.66 to 0.99. Bland-Altman plots confirmed that each variable provided no systematic shift between 3-dimensional motion analysis and clinic-based methods, and there was no association between difference and average. A developed regression equation also supported model validity with > 75% prediction accuracy of high KAM using both the 3-dimensional motion analysis and clinic-based techniques. CONCLUSION: The current validation provides the critical next step to merge the gap between laboratory identification of injury risk factors and clinical practice. Implementation of the developed prediction tool to identify female athletes with high KAM may facilitate the entry of female athletes with high ACL injury risk into appropriate injury-prevention programs.

As more children and adolescents participate in sports and conditioning activities (sometimes without consideration for cumulative workload), it is important to establish age-appropriate training guidelines that may reduce the risk of sports-related injury and enhance athletic performance. The purpose of this article is to review the scientific evidence on youth strength and conditioning and to provide age-appropriate recommendations for integrating different strength and conditioning activities into a well-designed program that is safe, effective, and enjoyable. Integrative training is defined as a program or plan that incorporates general and specific strength and conditioning activities that enhance both health- and skill-related components of physical fitness. The cornerstone of integrative training is age-appropriate education and instruction by qualified professionals who understand the physical and psychosocial uniqueness of children and adolescents.

It is now possible to manipulate the murine genome and produce transgenic mice in which genes encoding myocardial proteins have been ablated, resulting in an altered myocardial performance. In this study, we quantitate myocardial performance in work-performing mouse heart preparations from euthyroid, hypothyroid, and hyperthyroid mice. Our results show that time to peak pressure (TPP) and time to half-relaxation (RT1/2), together with first derivatives of intraventricular pressure (+/- dP/dt), are significant indicators of the quality and quantity of systolic contraction and relaxation. We compared the normal control indicators of contraction and relaxation of three different mouse strains at minimum afterloads (approximately 50 mmHg) and preloads (approximately 5 ml/min) and found them identical in range. All indicators of myocardial performance were significantly higher in the hyperthyroid and lower in the hypothyroid compared with normal mice. The cardiac myosin heavy chain isoform transcript shift (alpha-->beta) associated with hypothyroidism was observed. Because sympathetic activity is greatly enhanced with hyperthyroidism, we studied the effects of isoproterenol and the beta-blocker sotalol on cardiac contractility. Only approximately 50% of the myocardial hyperactivity displayed by hyperthyroid mice could be attributed to beta-adrenergic activity.

Purpose: The objective of this study was to determine whether biomechanical and neuromuscular risk factors related to abnormal movement patterns increased in females, but not males, during the adolescent growth spurt. Methods: A total of 315 subjects participated in two testing sessions approximately 1 yr apart. Male and female subjects were classified on the basis of their maturation status as pubertal or postpubertal. Three trials of a drop vertical jump (DVJ) were collected. Maximum knee abduction angle and external moments were calculated during the DVJ deceleration phase using a three-dimensional motion analysis system. Changes in knee abduction from the first to second year were compared among four subject groups (female pubertal, female postpubertal, male pubertal, and male postpubertal). Results: There were no sex differences in peak knee abduction angle or moment during DVJ between pubertal males and females (P > 0.05). However, pubertal females increased peak abduction angle from first to second year (P < 0.001), whereas males demonstrated no similar change (P = 0.90) in the matched developmental stages. After puberty, the peak abduction angle and moment were greater in females relative to males (angle: female -9.3[degrees] +/- 5.7[degrees], male -3.6[degrees] +/- 4.6[degrees], P < 0.001; moment: female -21.9 +/- 13.5 N[middle dot]m, male -13.0 +/- 12.0 N[middle dot]m, P = 0.017). Conclusions: This study identified, through longitudinal analyses, that knee abduction angle was significantly increased in pubertal females during rapid adolescent growth, whereas males showed no similar change. In addition, knee abduction motion and moments were significantly greater for the subsequent year in young female athletes, after rapid adolescent growth, compared with males. The combination of longitudinal, sex, and maturational group differences indicates that early puberty seems to be a critical phase related to the divergence of increased anterior cruciate ligament injury risk factors

Background Athletes who return to sport participation after anterior cruciate ligament reconstruction (ACLR) have a higher risk of a second anterior cruciate ligament injury (either reinjury or contralateral injury) compared with non—anterior cruciate ligament— injured athletes. Hypotheses Prospective measures of neuromuscular control and postural stability after ACLR will predict relative increased risk for a second anterior cruciate ligament injury. Study Design Cohort study (prognosis); Level of evidence, 2. Methods Fifty-six athletes underwent a prospective biomechanical screening after ACLR using 3-dimensional motion analysis during a drop vertical jump maneuver and postural stability assessment before return to pivoting and cutting sports. After the initial test session, each subject was followed for 12 months for occurrence of a second anterior cruciate ligament injury. Lower extremity joint kinematics, kinetics, and postural stability were assessed and analyzed. Analysis of variance and logistic regression were used to identify predictors of a second anterior cruciate ligament injury. Results Thirteen athletes suffered a subsequent second anterior cruciate ligament injury. Transverse plane hip kinetics and frontal plane knee kinematics during landing, sagittal plane knee moments at landing, and deficits in postural stability predicted a second injury in this population (C statistic = 0.94) with excellent sensitivity (0.92) and specificity (0.88). Specific predictive parameters included an increase in total frontal plane (valgus) movement, greater asymmetry in internal knee extensor moment at initial contact, and a deficit in single-leg postural stability of the involved limb, as measured by the Biodex stability system. Hip rotation moment independently predicted second anterior cruciate ligament injury (C = 0.81) with high sensitivity (0.77) and specificity (0.81). Conclusion Altered neuromuscular control of the hip and knee during a dynamic landing task and postural stability deficits after ACLR are predictors of a second anterior cruciate ligament injury after an athlete is released to return to sport.

Prospective measures of high knee abduction moment during landing identify female athletes at high risk for non-contact anterior cruciate ligament injury. Biomechanical laboratory measurements predict high knee abduction moment landing mechanics with high sensitivity (85%) and specificity (93%). The purpose of this study was to identify correlates to laboratory-based predictors of high knee abduction moment for use in a clinic-based anterior cruciate ligament injury risk prediction algorithm. The hypothesis was that clinically obtainable correlates derived from the highly predictive laboratory-based models would demonstrate high accuracy to determine high knee abduction moment status.Female basketball and soccer players (N=744) were tested for anthropometrics, strength and landing biomechanics. Pearson correlation was used to identify clinically feasible correlates and logistic regression to obtain optimal models for high knee abduction moment prediction.Clinical correlates to laboratory-based measures were identified and predicted high knee abduction moment status with 73% sensitivity and 70% specificity. The clinic-based prediction algorithm, including (Odds Ratio: 95% confidence interval) knee valgus motion (1.43:1.30-1.59 cm), knee flexion range of motion (0.98:0.96-1.01 degrees ), body mass (1.04:1.02-1.06 kg), tibia length (1.38:1.25-1.52 cm) and quadriceps to hamstring ratio (1.70:1.06-2.70) predicted high knee abduction moment status with C statistic 0.81.The combined correlates of increased knee valgus motion, knee flexion range of motion, body mass, tibia length and quadriceps to hamstrings ratio predict high knee abduction moment status in female athletes with high sensitivity and specificity.Utilization of clinically obtainable correlates with the prediction algorithm facilitates high non-contact anterior cruciate ligament injury risk athletes' entry into appropriate interventions with the greatest potential to prevent injury.

The aims of this study were to determine the prevalence and incidence of patellofemoral pain (PFP) in young female athletes and prospectively evaluate measures of frontal plane knee loading during landing to determine their relationship to development of PFP. We hypothesized that increased dynamic knee abduction measured during preseason biomechanical testing would be increased in those who developed PFP relative to teammates who did not develop PFP.Middle and high school female athletes (n=240) were evaluated by a physician for PFP and for landing biomechanics prior to their basketball season. The athletes were monitored for athletic exposures and PFP injury during their competitive seasons.At the beginning of the season, the point prevalence of PFP was 16.3 per 100 athletes. The cumulative incidence risk and rate for the development of new unilateral PFP was 9.66 per 100 athletes and 1.09 per 1000 athletic exposures, respectively. All new PFPs developed in middle school athletes who demonstrated mean International Knee Documentation Committee score of 85.6+/-7.7 at diagnosis. The new PFP group demonstrated increased knee abduction moments at initial contact (95% CI: 0.32 to 4.62Nm) on the most-symptomatic limb and maximum (95% CI: 1.3 to 10.1Nm; P=0.02) on the least-symptomatic (or no symptoms) limb relative to the matched control limbs. Knee abduction moments remained increased in the new PFP group when normalized to body mass (P0.05).The increased knee abduction landing mechanics in the new PFP group indicate that frontal plane loads contribute to increased incidence of PFP.

BACKGROUND: The incidence of anterior cruciate ligament (ACL) injuries among females continues at disproportionate rates compared to males, with research indicating inconclusive multifactorial causality. Data from previous retrospective studies suggest an effect of abnormal foot and ankle biomechanics on pathology at the knee, including the ACL. OBJECTIVE: To determine if a relationship exists between plantar foot loading patterns during normal gait and high risk biomechanics purported to increase risk of ACL injury. METHODS: Dynamic barefoot plantar pressure distribution was measured on 33 female collegiate soccer players. Groups were divided according to their predominant gait loading pattern (medial or lateral). Three dimensional (3-D) motion analysis was conducted during drop vertical jumps to assess vertical ground reaction force and discrete angle and joint moment variables of the lower extremities. RESULTS: No significant differences occured in sagittal or coronal plane knee joint kinematics and kinetics between the medial and lateral loading groups. DISCUSSION: Dynamic foot and ankle biomechanics during gait do not appear to be related to lower extremity kinematics or kinetics during landing in collegiate female soccer players. CONCLUSION: The exact cause of the abnormal differences in female landing biomechanics has not been irrefutably defined. This study suggests no effect of foot and ankle biomechanics exists on the landing mechanics of female soccer players.

Pain from osteoarthritis, the leading cause of disability in older patients, affects gait mechanics. Wearing an unloading brace may improve gait symmetry, decrease symptomatic pain, and increase activity for patients who have osteoarthritis of the knee or other varus knee deformities. Brace use may contribute to improved knee proprioception, gait parameters, and pain scores. Clinicians can recommend a trial of brace wear for patients who have knee pain as a conservative measure or to provide temporary pain relief before joint replacement surgery.

Neuromuscular training has a significant effect on reducing relative ACL injury risk in female athletes in high-risk landing and cutting sports like soccer, basketball, volleyball, and team handball.

Objective. The purpose of this study was to determine if high functioning children with Juvenile Idiopathic Arthritis (JIA) with minimal disease activity have different biomechanics during high loading tasks compared to controls. Patients were included if they had minimal inflammation documented in one or both knees. Methods. The subject groups consisted of eleven patients with JIA and eleven sex, age, height, and weight matched controls. Sagittal plane kinematic and kinetics were calculated during a drop vertical jump maneuver. The Child Health Assessment Questionnaire (CHAQ) was collected on each patient with JIA. Results. The subjects with JIA had increased knee ( 𝑃 = . 0 1 1 ) and hip flexion ( 𝑃 < . 0 0 1 ) compared to control subjects. Subjects with JIA also demonstrated decreased knee extensor moments during take-off ( 𝑃 = . 0 2 8 ) and ankle plantar flexor moments during landing ( 𝑃 = . 0 2 4 ) and take-off ( 𝑃 = . 0 0 4 ). In the JIA group, increased hip extensor moments were predictive of increased disability ( 𝑅 2 = . 4 7 7 , 𝑆 𝐸 𝐸 = . 1 3 1 ). Conclusions. Patients with JIA may demonstrate underlying biomechanical deviations compared to controls. In addition, biomechanical assessment of hip extensor mechanics during dynamic tasks may provide an objective assessment tool to determine overall function in patients with JIA.

FEMALE ATHLETES demonstrate a 4 to 6 times higher incidence of non-contact anterior cruciate ligament (ACL) injury than male athletes participating in the same landing and pivoting sports.1-3 This greater risk of ACL injury, coupled with a dramatic increase in participation (doubling each decade), has led to a significant rise in the number of ACL injuries in female athletes. This gender disparity in non-contact ACL injury risk, combined with evidence that the primary cause may be neuromuscular in nature, have lead to the development of neuromuscular interventions designed to prevent injury.4-9 Initial interventions aimed at reducing the incidence of ACL injuries in female athletes were developed based on empirical evidence from coaching and training female athletes and from performance enhancement research.4,10 More current techniques, developed from identified injury mechanism (dynamic knee valgus11) and objective analysis of training methods,12-19 may further reduce traumatic ACL injuries in female athletes.5-7 The programs that have demonstrated ACL injury reduction are comprehensive, and include multiple training components that may induce the neuromuscular changes. The purpose of this report is to discuss the current evidence related to modifiable ACL injury mechanisms during landing and to present a novel “clinician-friendly” assessment and training technique that can be used to identify these mechanisms in high-risk female athletes. Key Points Use of the tuck jump assessment to identify neuromuscular imbalances may provide direction for targeted treatment for those at high risk for ACL injury. Improvement in neuromuscular techniques may be assessed and continually monitored with repeated measurement using the tuck jump assessment. Multiple factors may underlie the differences in ACL injury risk in male and females, neuromuscular control may be the most important and modifiable factor that can be addressed with plyometric training.

Side-to-side differences in lower-extremity biomechanics may be predictive of increased risk of lower-extremity injuries in athletes. The purpose of this report is to provide field testing methodology for tests designed to isolate lower-extremity asymmetry and to demonstrate the potential for these tests to provide reliable measures. Six athletes (3 females, 3 males) were tested on 2 consecutive days for activities incorporated into a replicated National Football League (NFL) combine setting. Vertical hop power (VHP) and jump height were measured on a portable force platform as athletes performed maximum effort hops for 10 seconds. The modified agility T-test (MAT) incorporates two 90-degree single-leg cuts during the trial and was measured as total time for completion. Intraclass correlations (within ICC [3,k], between ICC [3,1]) were calculated. The VHP test had good to excellent within-session reliability for peak power of both the right (ICC = 0.942) and left (ICC = 0.895) sides. Jump height showed excellent within-session reliability for both the right (ICC = 0.963) and left (ICC = 0.940) sides. The between-session reliability for peak power between jumps was good for the right (ICC = 0.748) and left (ICC = 0.834) sides. Jump height showed good to excellent between-session reliability on the right (ICC = 0.794) and left (ICC = 0.909) sides. The MAT also showed good reliability between days (ICC = 0.825).The results indicate that the VHP test provides reliable assessment of both within- and between-session jump height and power production. The MAT also provides good reliability between testing days. Both the VHP and the MAT may be useful for clinicians to identify the presence of lower-limb asymmetry and potential injury risk factors in athletic populations.

Traditional methods employed to study musculoskeletal injury mechanisms and joint biomechanics utilise in vivo or in vitro techniques. The advent of new technology and improved methods has also given rise to in silico (computer modelling) techniques. Under the current research paradigm, in vivo, in vitro and in silico methods independently provide information regarding the mechanisms and prevention of musculoskeletal injury. However, individually, each of these methods has multiple, inherent limitations and is likely to provide incomplete answers about multifactorial, complex injury conditions. The purpose of this treatise is to review current methods used to study, understand, and prevent musculoskeletal injury and to develop new conceptual-methodological frameworks that may help create a paradigm shift in musculoskeletal injury prevention research. We term the fusion of these three techniques in simulacra amalgama, or simply in sim, meaning a “union of models done on the likeness of phenomena.” Anterior cruciate ligament (ACL) injury will be employed as a model example for the utility and applicability of the proposed, synthesised approach. Shifting the current experimental paradigm to incorporate a multifaceted, multidisciplinary, integration of in vivo, in vitro and in silico methods into the proposed in sim approaches may provide a platform for a more comprehensive understanding of the relationships between complex joint biomechanics and observed injury mechanisms.

Myer, GD, Quatman, CE, Khoury, J, Wall, EJ, and Hewett, TE. Youth versus adult “weightlifting” injuries presenting to united states emergency rooms: accidental versus nonaccidental injury mechanisms. J Strength Cond Res 23(7): 2054–2060, 2009—Resistance training has previously been purported to be unsafe and ineffective in children. The purpose of this investigation was to evaluate resistance training-related injuries presenting to U.S. emergency rooms by age, type, and mechanism of injury. We hypothesized that older athletes would sustain greater percentages of joint sprains and muscle strains, whereas younger athletes would sustain a greater percentage of accidental injuries that would result in an increased percentage of fractures in youths. The U.S. Consumer Product Safety Commission (CPSC) National Electronic Injury Surveillance System was queried from 2002 to 2005 using the CPSC code for “Weightlifting.” Subjects between the ages of 8 and 30 were grouped by age categories 8 to 13 (elementary/middle school age), 14 to 18 (high school), 19 to 22 (college), and 23 to 30 (adult). Injuries were classified as “accidental” if caused by dropped weight or improper equipment use. Multiple logistic regression was used to compare accidental injuries between age groups. The sample consisted of 4, 111 patients. Accidental injuries decreased (p < 0.05) with age: 8 to 13 > 14 to 18 > 19 to 22 years = 23 to 30 years. Conversely, sprain/strain injuries increased in each successive age group (p < 0.05). Evaluation of only the nonaccidental injuries (n = 2, 565) showed that the oldest categories (19–22 and 23–30 yr) demonstrated a greater percentage of sprains and strains relative to younger age categories (p < 0.001). Two thirds of the injuries sustained in the 8 to 13 group were to the hand and foot and were most often related to “dropping” and “pinching” in the injury descriptions, and there was an increased percentage of fractures in the 8 to 13 group relative to all other groups (p < 0.001). The study findings indicate that children have lower risk of resistance training-related joint sprains and muscle strains than adults. The majority of youth resistance training injuries are the result of accidents that are potentially preventable with increased supervision and stricter safety guidelines.

The relationship between generalized joint laxity and plantar pressure distribution of the foot and the potential implications for lower extremity injury have not been studied.Context:To determine the relationship between generalized joint laxity and dynamic plantar pressure distribution. We hypothesized that individuals with greater generalized joint laxity, or hypermobility, would have greater dynamic medial midfoot pressure and loading during walking than nonhypermobile individuals.Objective:Case control.Design:Institutional biomechanics laboratory.Setting:Participants included 112 female soccer players between 11 and 21 years of age.Patients or Other Participants:Each participant was tested for generalized joint laxity using the Beighton and Horan Joint Mobility Index (BHJMI; range, 0–9) and was categorized as having either high (BHJMI score ≥4) or low (BHJMI score Peak pressure and maximum force were greater in the 27 participants categorized as having high generalized joint laxity than in the 85 participants categorized as having low generalized joint laxity. The midfoot region exhibited greater loading in participants with high generalized joint laxity than in the other participants. We found an effect of BHJMI classification in the medial midfoot; peak pressure in the dominant (F1,109 = 11.262, P = .001) and nondominant (F1,109 = 14.32, P < .001) sides and maximum force in the dominant (F1,109 = 7.88, P = .006) and nondominant (F1,109 = 9.18, P = .003) sides were greater in the high generalized joint laxity group than in the low generalized joint laxity group.Results:Athletes classified as having high generalized joint laxity demonstrated increased midfoot loading. Delineation of risk factors for medial collapse of the foot, which include hypermobility in athletes, may help clinicians evaluate and prevent lower extremity injury with treatments, such as orthoses.Conclusions

Biomechanical factors, such as hip and knee extensor moments, related to drop jump (DJ) performance have not been investigated in adolescent girls. The purpose of this study was to determine the key independent biomechanical variables that predict overall vertical jump performance in adolescent girls. Sixteen high school adolescent girls from club-sponsored and high school-sponsored volleyball teams performed DJ at 3 different drop heights (15, 30, and 45 cm). A motion analysis system consisting of 10 digital cameras and a force platform was used to calculate vertical jump height, joint angles, and joint moments during the tasks. A multiple linear regression was used to determine the biomechanical parameters that were best predictive of vertical jump height at each box drop distance. The 2 predictor variables in all 3 models were knee and hip extensor moments. The models predicted 82.9, 81.9, and 88% of the vertical jump height variance in the 15, 30, and 45 cm trials, respectively. The results of the investigation indicate that knee and hip joint moments are the main contributors to vertical jump height during the DJ in adolescent girls. Strength and conditioning specialists attempting to improve vertical jump performance should target power and strength training to the hip and knee extensors in their athletes.

Objective A multifactorial combination of predictors may increase anterior cruciate ligament (ACL) injury risk in athletes. The objective of this twin study was to examine these risk factors to identify commonalities in risk factors that predisposed female fraternal twins to ACL injury. Methods Female twins in high-risk sports were prospectively measured prior to an injury for neuromuscular control using three-dimensional motion analysis during landing, hamstrings and quadriceps muscular strength on a dynamometer and joint laxity using a modified Beighton–Horan index and a Compu-KT arthrometer. Intraoperative measures of femoral intercondylar notch width were recorded during ACL reconstruction. Results Abduction angles were increased at one knee in both of the twin sister athletes relative to uninjured controls at initial contact and at maximum displacement during landing. The twin female athletes that went on to ACL injury also demonstrated decreased peak knee flexion motion at both knees than uninjured females during landing. The twin athletes also had increased joint laxity and decreased hamstrings to quadriceps (H/Q) torque ratios compared to controls. Femoral intercondylar notch widths were also below the control mean in the twin siblings. Conclusions Prescreened mature female twins that subsequently experienced ACL injury demonstrated multiple potential risk factors including: increased knee abduction angles, decreased knee flexion angles, increased general joint laxity, decreased H/Q ratios and femoral intercondylar notch width.

OBJECTIVE: The purpose of the current investigation was to determine the association of quadriceps and hamstrings strength to ACL injury risk in female athletes. The primary hypothesis was that there would be decreased knee flexor and increased knee extensor strength in female athletes who went on to ACL injured status (FACL) compared to uninjured female (FC) and male (MC) control subjects. STUDY DESIGN: Matched case control SETTING: Institutional Biomechanics Laboratory PARTICIPANTS: Prospectively measured FACL (n=22) females who subsequently suffered confirmed non-contact ACL ruptures (16 during soccer and 6 during basketball play) were matched to (1:4 ratio) female controls (FC; n=88) using limb (dominant or non-dominant), pubertal status, sport and nearest height and mass. In addition, males (MC) were matched (1:1 ratio) to FACL to serve as a secondary comparative control. ASSESSMENT OF RISK FACTORS: Isokinetic (concentric) knee extension/flexion strength (300°/s). RESULTS: FACL subjects had decreased hamstrings strength compared to MC [15% (95% C.I. 1%, 27%); P=0.04]. FC were not different than MC in hamstrings strength. Conversely, FACL subjects did not differ compared to the MC in quadriceps strength and the FC demonstrated decreased quadriceps strength relative to MC [10% (95% C.I. 3%,18%); P=0.01]. CONCLUSIONS: The results of this investigation indicate that female athletes who suffered ACL injury subsequent to strength testing had a combination of decreased hamstrings, but not quadriceps, strength compared to males. In direct contrast, female athletes who did not go on to ACL injury had decreased quadriceps strength and similar hamstrings strength compared to matched male athletes.

The Cincinnati Children's Hospital Medical Center and Research Foundation, Sports Medicine Biodynamics Center and Human Performance Laboratory, Cincinnati, OH; University of Cincinnati College of Medicine, Departments of Pediatrics and Orthopaedic Surgery and the College of Engineering, Department of Biomedical Engineering and Rehabilitation Sciences, College of Allied Health Sciences, Cincinnati, OH; University of Kentucky, Department of Rehabilitation Sciences, College of Health Sciences, Lexington, KY

Limited proteolysis of gizzard myosin by alpha-chymotrypsin converted the heavy chain doublet pattern, seen by gel electrophoresis, to a single band. Light chain degradation was not observed and only minor cleavage occurred at other heavy chain sites. Using a polyclonal antibody raised against a unique sequence from the slower-migrating heavy chain (SM1) it was shown that this conversion was due to the loss of a peptide approximately 4000 daltons from the C terminus of SM1. The peptide was isolated and sequenced, and the cleavage site was identified between phenylalanine 1943 and alanine 1944. Addition of antibody before protease protected SM1 from cleavage. The following changes were observed (a) the Mg2(+)-dependence of actin-activated ATPase of digested phosphorylated myosin was altered and activity was relatively high at low Mg2+ levels, i.e. similar to phosphorylated heavy meromyosin; (b) the KCl dependence of Mg2(+)-ATPase of the digested myosin, particularly the phosphorylated form, showed an altered pattern consistent with the stabilization of the 6 S conformation; (c) the tendency for aggregation was increased by proteolysis of phosphorylated myosin. These results show that the C-terminal region of a gizzard myosin heavy chain can modify some of the properties of myosin. It is suggested that the observed modifications reflect an enhanced tendency of the digested myosin to aggregate.

Background: The purpose of the present study was to determine if patient age, lesion size, lesion location, presenting knee symptoms, and sex predict the healing status after six months of a standard protocol of nonoperative treatment for stable juvenile osteochondritis dissecans of the knee. Methods: Forty-two skeletally immature patients (forty-seven knees) who presented with a stable osteochondritis dissecans lesion were included in the present study. All patients were managed with temporary immobilization followed by knee bracing and activity restriction. The primary outcome measure of progressive lesion reossification was determined from serial radiographs every six weeks, for up to six months of nonoperative treatment. A multivariable logistic regression model was used to determine potential predictors of healing status from the listed independent variables. Results: After six months of nonoperative treatment, sixteen (34%) of forty-seven stable lesions had failed to progress toward healing. The mean surface area (and standard deviation) of the lesions that showed progression toward healing (208.7 ± 135.4 mm2) was significantly smaller than that of the lesions that failed to show progression toward healing (288.0 ± 102.6 mm2) (p = 0.05). A logistic regression model that included patient age, normalized lesion size (relative to the femoral condyle), and presenting symptoms (giving-way, swelling, locking, or clicking) was predictive of healing status. Age was not a significant contributor to the predictive model (p = 0.25). Conclusions: In two-thirds of immature patients, six months of nonoperative treatment that includes activity modification and immobilization results in progressive healing of stable osteochondritis dissecans lesions. Lesions with an increased size and associated swelling and/or mechanical symptoms at presentation are less likely to heal. Level of Evidence: Prognostic Level II. See Instructions to Authors for a complete description of levels of evidence.

Objectives: To systematically review the current literature that relates the effects of age and skill level to motor control patterns of knee musculature co-contraction during functional movements. Methods: A search of electronic databases was performed with the search terms specifying co-contraction (cocontract*, co-contract*, coactive* or co-activ*). The search was focused on the effects age and/or skill level and were limited by the keywords of age or skill level (skill*) or experience (experi*). Results: The search yielded a total of six peer-reviewed manuscripts that met the search criteria and were included in the review. Conclusions: The relationship between adequate dynamic joint stability and efficient movement patterns are complex. Co-contraction related to age and skill development varies among studies due to technical and practical considerations. Adequate antagonistic co-contraction of hamstring musculature seems to be a component of all functional movements, possibly maintain dynamic knee stability and protect against excessive joint loads. Future investigations that further delineate the appropriate lower extremity agonist and antagonist relationships during dynamic tasks may help elucidate injury risk mechanisms in specific populations.

Purpose: Biomechanical measures quantified during dynamic tasks with coupled epidemiological data in longitudinal experimental designs may be useful to determine which mechanisms underlie injury risk in young athletes. A key component is the ability to reliably measure biomechanical variables between testing sessions. The purpose was to determine the reliability of three-dimensional (3D) lower-extremity kinematic and kinetic variables during landing in young athletes measured within a session and between two sessions 7 wk apart. Methods: Lower-extremity kinetics and kinematics were quantified during a drop vertical jump. Coefficient of multiple correlations (CMC), intraclass correlation coefficients (ICC (3, k), ICC (3, 1)), and typical error (TE) analyses were used to examine within- and between-session reliability. Results: There were no differences in within-session reliability for peak angular rotations between planes with all discrete variables combined (sagittal ICC >= 0.933, frontal ICC >= 0.955, transverse ICC >= 0.934). Similarly, the between-session reliability of kinematic measures were not different between the three planes of motion but were lower than the within-session ICC. The within- and between-session reliability of discrete joint moment variables were excellent for all sagittal (within ICC >= 0.925, between ICC >= 0.800) and frontal plane moment measures (within ICC >= 0.778, between ICC >= 0.748). CMC analysis revealed similar averaged within-session (CMC = 0.830 +/- 0.119) and between-session (CMC = 0.823 +/- 0.124) waveform comparisons. Conclusion: The majority of the kinematic and kinetic variables in young athletes during landing have excellent to good reliability. The ability to reliably quantify lower-extremity biomechanical variables of young athletes during dynamic tasks over extended intervals may aid in identifying potential mechanisms related to injury risk factors.

Our purpose was to determine if females demonstrate decreased hamstrings to quadriceps peak torque (H/Q) ratios compared to males and if H/Q ratios increase with increased isokinetic velocity in both sexes. Maturation disproportionately increases hamstrings peak torque at high velocity in males, but not females. Therefore, we hypothesised that mature females would demonstrate decreased H/Q ratios compared to males and the difference in H/Q ratio between sexes would increase as isokinetic velocity increased. Studies that analysed the H/Q ratio with gravity corrected isokinetic strength testing reported between 1967 and 2004 were included in our review and analysis. Keywords were hamstrings/quadriceps, isokinetics, peak torque and gravity corrected. Medline and Smart databases were searched combined with cross-checked bibliographic reference lists of the publications to determine studies to be included. Twenty-two studies were included with a total of 1568 subjects (1145 male, 423 female). Males demonstrated a significant correlation between H/Q ratio and isokinetic velocity (R=0.634, p

Loss of cardiac myocytes in heart failure is thought to occur largely through an apoptotic process. Here we show that heart failure can also be precipitated through myocyte necrosis associated with Ca2+ overload. Inducible transgenic mice with enhanced sarcolemmal L-type Ca2+ channel (LTCC) activity showed progressive myocyte necrosis that led to pump dysfunction and premature death, effects that were dramatically enhanced by acute stimulation of beta-adrenergic receptors. Enhanced Ca2+ influx-induced cellular necrosis and cardiomyopathy was prevented with either LTCC blockers or beta-adrenergic receptor antagonists, demonstrating a proximal relationship among beta-adrenergic receptor function, Ca2+ handling, and heart failure progression through necrotic cell loss. Mechanistically, loss of cyclophilin D, a regulator of the mitochondrial permeability transition pore that underpins necrosis, blocked Ca2+ influx-induced necrosis of myocytes, heart failure, and isoproterenol-induced premature death. In contrast, overexpression of the antiapoptotic factor Bcl-2 was ineffective in mitigating heart failure and death associated with excess Ca2+ influx and acute beta-adrenergic receptor stimulation. This paradigm of mitochondrial- and necrosis-dependent heart failure was also observed in other mouse models of disease, which supports the concept that heart failure is a pleiotropic disorder that involves not only apoptosis, but also necrotic loss of myocytes in association with dysregulated Ca2+ handling and beta-adrenergic receptor signaling.

Female athletes who are at increased risk for anterior cruciate ligament (ACL) injury demonstrate biomechanical differences between limbs during athletic tasks that may persist following anterior cruciate ligament reconstruction (ACLR). This may limit an athlete's potential for safe return to sports competition. The purpose of this study was to determine if female athletes demonstrate lower limb asymmetries in landing and takeoff force following ACLR and clearance for return to competitive sports participation. We hypothesized that females following ACLR would demonstrate side-to-side differences in landing and jumping kinetics after their return to sport (2+ years) that would not be observed in a group of healthy female controls.Case control study.The Sports Medicine Biodynamics Center at Cincinnati Children's Hospital Medical Center.Fourteen female athletes at a mean of 27 months following ACLR and 18 healthy female athletes participated in the study.All subjects executed a drop vertical jump (DVJ) task onto 2 force plates. Vertical ground reaction force (VGRF) was measured during landing and takeoff and was used to calculate landing phase loading rates. A 2-way analysis of variance was used to determine differences between the involved, uninvolved, and control limbs.Females who had undergone ACLR demonstrated increased VGRF (P = 0.001) and loading rate (P0.001) on the uninvolved limb during landing when compared with the involved limb and the control group. During takeoff, the involved limb showed significantly less ability to generate force (P = 0.03) than the uninvolved limb and the control limbs.Female athletes who have undergone ACLR and returned to sport may continue to demonstrate biomechanical limb asymmetries 2 years or more after reconstruction that can be identified during landing.

Our purpose was to examine the effects of pubertal status on generalized joint laxity in a population of male and female athletes. We hypothesized that females would show higher generalized joint laxity after the onset of puberty while males would not. This cross-sectional cohort study included 275 female and 143 male middle school and high school basketball and soccer athletes. Joint laxity was assessed using the Beighton and Horan Joint Mobility Index. BHJMI scores were averaged and female and male athletes were compared by pubertal stage. Females demonstrated increased joint laxity scores between pre-pubertal and post-pubertal groups (P=0.042), while males did not. Pre-pubertal male and female athletes were not different in cumulative joint laxity scores (female pre-puberty Mean=2.00; male pre-pubertal Mean=1.66). However, following the onset of puberty females (pubertal Mean=2.96; post-pubertal Mean= 3.03) demonstrated a greater joint laxity score compared to males (pubertal Mean=1.24; post-pubertal Mean=1.30). Gender differences in BHJMI score was found at puberty and post-puberty (P

Female athletes are four to six times more likely to sustain an anterior cruciate ligament (ACL) injury than male athletes. Since the enactment of Title IX, male athletic participation at the high school level has remained steady (3.8 million), whereas female athletic participation has increased tenfold (from 0.3 to 3.0 million). Geometric growth in athletic participation and the higher injury rate in female athletes have led to gender inequity in ACL injury rates. Most ACL injuries occur as a result of noncontact mechanisms such as during landing from a jump or while making a lateral pivot. Dynamic knee instability, caused by ligament dominance (decreased dynamic neuromuscular control of the joint), quadriceps dominance (decreased hamstring strength and recruitment), and leg dominance (side-to-side differences in strength and coordination) may be responsible for gender inequity in ACL injury rates.

Background Neuromuscular training may reduce risk factors that contribute to ACL injury incidence in female athletes. Multi-component, ACL injury prevention training programs can be time and labor intensive, which may ultimately limit training program utilization or compliance. The purpose of this study was to determine the effect of neuromuscular training on those classified as "high-risk" compared to those classified as "low-risk." The hypothesis was that high-risk athletes would decrease knee abduction moments while low-risk and control athletes would not show measurable changes. Methods Eighteen high school female athletes participated in neuromuscular training 3×/week over a 7-week period. Knee kinematics and kinetics were measured during a drop vertical jump (DVJ) test at pre/post training. External knee abduction moments were calculated using inverse dynamics. Logistic regression indicated maximal sensitivity and specificity for prediction of ACL injury risk using external knee abduction (25.25 Nm cutoff) during a DVJ. Based on these data, 12 study subjects (and 4 controls) were grouped into the high-risk (knee abduction moment >25.25 Nm) and 6 subjects (and 7 controls) were grouped into the low-risk (knee abduction Results Athletes classified as high-risk decreased their knee abduction moments by 13% following training (Dominant pre: 39.9 ± 15.8 Nm to 34.6 ± 9.6 Nm; Non-dominant pre: 37.1 ± 9.2 to 32.4 ± 10.7 Nm; p = 0.033 training X risk factor interaction). Athletes grouped into the low-risk category did not change their abduction moments following training (p > 0.05). Control subjects classified as either high or low-risk also did not significantly change from pre to post-testing. Conclusion These results indicate that "high-risk" female athletes decreased the magnitude of the previously identified risk factor to ACL injury following neuromuscular training. However, the mean values for the high-risk subjects were not reduced to levels similar to low-risk group following training. Targeting female athletes who demonstrate high-risk knee abduction loads during dynamic tasks may improve efficacy of neuromuscular training. Yet, increased training volume or more specific techniques may be necessary for high-risk athletes to substantially decrease ACL injury risk.

Menstrual cycle phase has been correlated with risk of noncontact anterior cruciate ligament injury in women. The mechanism by which hormonal cycling may affect injury rate is unknown.Jumping and landing activities performed during different phases of the menstrual cycle lead to differences in foot strike knee flexion, as well as peak knee and hip loads, in women not taking an oral contraceptive but not in women taking an oral contraceptive. Women will experience greater normalized joint loads than men during these activities.Controlled laboratory study.Twenty-five women (13 using oral contraceptives) and 12 men performed repeated trials of a horizontal jump, vertical jump, and drop from a 30-cm box on the left leg. Lower limb kinematics (foot strike knee flexion) and peak externally applied moments were calculated (hip adduction moment, hip internal rotation moment, knee flexion moment, knee abduction moment). Men were tested once. Women were tested twice for each phase of the menstrual cycle (follicular, luteal, ovulatory), as determined from serum analysis. An analysis of variance was used to examine differences between phases of the menstrual cycle and between groups (alpha = .05).No significant differences in moments or knee angle were observed between phases in either female group or between the 2 female groups or between either female group and the male controls.Variations of the menstrual cycle and the use of an oral contraceptive do not affect knee or hip joint loading during jumping and landing tasks.Because knee and hip joint loading is unaffected by cyclic variations in hormone levels, the observed difference in injury rates is more likely attributable to persistent differences in strength, neuromuscular coordination, or ligament properties.

Background In sports involving pivoting and landing, female athletes suffer knee injury at a greater rate than male athletes. Hypotheses Proprioceptive deficits in control of the body's core may affect dynamic stability of the knee. Female, but not male, athletes who suffered a knee injury during a 3-year follow-up period would demonstrate decreased core proprioception at baseline testing as compared with uninjured athletes. Study Design Cohort study (prognosis); Level of evidence, 2. Methods Study subjects were 277 collegiate athletes (140 female, 137 male) who were prospectively tested for core proprioception by active and passive proprioceptive repositioning. Athletes were monitored for injury for 3 years. An ANOVA and multivariate logistic regression were used to test whether core proprioception was related to knee injuries in athletes. Results Twenty-five athletes sustained knee injuries (11 women, 14 men). Deficits in active proprioceptive repositioning were observed in women with knee injuries (2.2°) and ligament/meniscal injuries (2.4°) compared with uninjured women (1.5°, P ≤ .05). There were no differences in average active proprioceptive repositioning error between injured men and uninjured men (P ≥ .05). Uninjured women demonstrated significantly less average error in active proprioceptive repositioning than uninjured men (1.5° vs 1.7°, P ≤ .05). For each degree increase in average active proprioceptive repositioning error, a 2.9-fold increase in the odds ratio of knee injury was observed, and a 3.3-fold increase in odds ratio of ligament/meniscal injury was observed (P ≤ .01). Active proprioceptive repositioning predicted knee injury status with 90% sensitivity and 56% specificity in female athletes. Conclusions Impaired core proprioception, measured by active proprioceptive repositioning of the trunk, predicted knee injury risk in female, but not male, athletes.

Knee dislocations with multi-ligamentous involvement are potentially limb-threatening injuries that require extensive surgical and rehabilitative intervention. These knee injuries, such as combined anterior cruciate ligament, posterior cruciate ligament, medial collateral ligament and/or lateral collateral ligament injuries, are devastating injuries with results that vary from total disability to nearly full recovery of function. Recent surgical advances, including the use of allograft tissues, have increased the efficacy of these procedures while posing new challenges. By combining scientifically based surgical and rehabilitative approaches, improved outcomes in these difficult cases are being reported in the orthopaedic literature. This review details the epidemiology and biomechanics of these serious knee ligament injuries. In addition, state-of-the-art surgical and rehabilitative techniques will be outlined. Clinical and diagnostic imaging evaluation of these knee injuries is reviewed in order to plan and execute the surgical and rehabilitative practices. We review the basic science, surgical and rehabilitative theories and practices associated with bringing patients with these serious knee injury injuries to full recovery, and detail the development of strategies for developing protocols to address these complicated cases.

Objectives: Over 125,000 anterior cruciate ligament (ACL) injuries occur each year in the United States. External loads on the knee in the frontal plane, specifically the knee abduction moment (KAM), predict future ACL injury with high sensitivity and specificity. The purpose of this randomized controlled trial (RCT) was to determine if biomechanical and neuromuscular factors could be used to characterize athletes by distinct factor profiles, to examine if neuromuscular training (NMT) would decrease the potential risk factors, and if NMT would preferentially benefit athletes that exhibited specific risk profiles. The hypotheses tested were: 1) a priori chosen biomechanical and neuromuscular factors would characterize subjects into distinct at-risk profiles, 2) NMT would decrease biomechanical and neuromuscular factors related to increased injury risk and 3) the decrease in these biomechanical and neuromuscular factors would be greater in those athletes characterized by the overall higher risk profiles. Methods: A total of 624 female athletes from 52 basketball, soccer and volleyball teams participated and were screened prior to their competitive season. During the pre-season testing, the athletes performed 3 different types of tasks for which biomechanical measures were taken: 1) drop vertical jump (DVJ), 2) single leg drop (SLD), and 3) single leg cross drop (SCD) landings. Using data from these tasks a latent profile analysis (LPA) was conducted to identify distinct profiles based on pre-intervention biomechanical and neuromuscular measures. As a validation, we examined whether the profile membership was significant predictor of KAM. Analysis of Co-Variance (ANCOVA) was used to examine treatment effects of NMT on biomechanical and neuromuscular measures in the 375 athletes who completed both pre- and post-intervention tasks. Differences were considered statistically significant at pResults: LPA using six pre-intervention biomechanical measures selected a priori resulted in three distinct profiles. Athletes in profiles II and III had significant higher KAM, compared to Profile I. The Core/Trunk-based NMT significantly increased hip external rotation moments and moment impulse and increased peak trunk flexion and decreased extension. In addition, the treatment effect of NMT varied by pre-intervention risk profile. Athletes with pre-intervention risk Profile II and III (higher risk) had a more significant treatment effect of NMT than Profile I. Conclusion: This is the first study to use LPA analysis of biomechanical landing data to create KAM and potentially ACL injury risk profiles. The LPA of multiple biomechanical and neuromuscular measures identified three distinct risk groups; associated with differences in peak KAM Analysis of the RCT showed that NMT significantly increased hip external rotation moments and moment impulse and increased peak trunk flexion and decreased extension, and that alterations in risk factors are different across risk profile group, with higher risk groups showing an overall significant improvement in KAM. These findings show the existence of discernable groups of athletes that are more appropriate for NMT intervention; further study is needed in even larger cohorts to investigate ACL injury as our primary outcome variable.

Objectives: Loss of quadriceps strength after anterior cruciate ligament (ACL) injury and reconstruction (ACLR) is a common and debilitating complicating factor. The association between the recovery of quadriceps strength and functional outcomes after ACLR is a focus of current study, while evaluation of the recovery of hamstrings strength is limited despite use of hamstrings autografts. Decreased hamstrings activation increases risk of a primary ACL injury; however, the effect of hamstring strength on post-operative knee function is unknown. We hypothesized that improvement in quadriceps and hamstrings strength would correlate with improvements in self-reported outcome (SRO) measures in the first six months after ACLR. Methods: Thirty subjects (20 males / 10 females) diagnosed with acute ACL rupture that underwent ACLR with hamstrings autograft were enrolled in the study. Subjects were between the ages of 14 and 44 who previously had participated in level I/II pivoting/cutting sports. Subjects underwent isokinetic quadriceps and hamstrings strength assessment at 60 degrees/second (Biodex System III, Shirley, NY) prior to surgery and at 12, and 24 weeks post-operatively. Quadriceps and hamstrings limb symmetry indexes [(involved strength/uninvolved strength) x 100] were calculated at each time point. The Knee Injury Osteoarthritis Outcome Score (KOOS subscales Pain, Symptoms, ADL, Quality of Life (QOL) and Sport) was administered at each time point. Pearson's correlation was utilized to determine the relationships between changes in quadriceps index (QI), hamstrings index (HI), and SRO measures between each time point. Results: Mean QI pre-ACLR, 12 weeks and 24 weeks post-ACLR were 78.3%, 76.7%, and 83.7% respectively. Mean HI at the same time points were 78.5%, 71.6% and 82.8% respectively. Improvements in QI were correlated with improvement on the KOOS-Sport at each time point (pre-ACLR to 12 weeks post-ACLR: r= 0.65; pre-ACLR to 24 weeks post-ACLR: r= 0.66; 12 weeks post-ACLR to 24 weeks post-ACLR: r= 0.69; p < 0.001) as well as KOOS-QOL pre-operative to 12 weeks post-ACLR (r= 0.38, p < 0.05). Improvements in HI were correlated with KOOS-Pain from the pre-operative to 12 and 24 weeks post-ACLR (r = 0.47 and r= 0.44 respectively; p < 0.04). Improvements in HI and QI were related to improvements on KOOS-Symptoms from pre-operative to 24 weeks post-ACLR (r = 0.43 and r= 0.51 respectively; p < 0.05) while QI and KOOS-Symptoms also improved from pre-operative to 12 weeks post-ACLR (r = 0.39, p < 0.04). Conclusion: Positive correlations were seen between QI and multiple SRO measures over time. Associations between HI and KOOS-Symptoms and Pain subscales were found early in post-operative recovery; there was no association between changes in HI and KOOS-ADL, Sport or QOL subscales at any time point. Correlations between HI and KOOS-Pain and Symptoms may be representative of pain and inflammation associated with hamstrings graft harvest, which resolve over time. These results support current literature demonstrating the relationship between the recovery of quadriceps strength and self-reported function post-ACLR. Continued focus on restoration of quadriceps strength is imperative to maximize functional outcomes post-ACLR.

Objectives: Knee laxity in the setting of suspected anterior cruciate ligament (ACL) injury is frequently assessed through physical examination using the Lachman, pivot-shift, and anterior drawer tests. The degree of laxity noted on these examinations may influence treatment decisions and prognosis. We hypothesized that increased pre-operative knee laxity (Grade 3+ pivot-shift, Lachman > 10mm, or anterior drawer greater than 10mm) are associated with increased risk of revision ACL reconstruction and poorer patient-reported outcomes at two years post-operative. Methods: From an ongoing prospective cohort study, 1394 patients that underwent primary isolated ACL reconstruction within 3 months of injury with autograft tissue without medial collateral, lateral collateral, or posterior cruciate injury requiring treatment or prior contralateral ACL injury were identified. Demographic data, physical examination findings under anesthesia at the time of ACL reconstruction, information regarding meniscus status and treatment, and pre-operative and 2 year post-operative International Knee Documentation Committee (IKDC), Knee Injury and Osteoarthritis Outcome Score Knee Related Quality of Life subscale (KOOS-QOL), and Marx activity scores were collected. Patients reported by the operating surgeons as having a Lachman or anterior drawer examination at least 10mm greater than the contralateral side were classified as having a high grade Lachman or anterior drawer respectively. Patients reported by the operating surgeon as having a 3+ pivot-shift were classified as having a high-grade pivot-shift. Patients demonstrating high-grade laxity on any of these examinations were classified as having high-grade pre-operative knee laxity. Multiple logistic regression modeling was used to evaluate whether having high-grade pre-operative laxity was associated with increased odds of undergoing revision ACL reconstruction within 2 years of the index procedure, controlling for patient age, sex, activity level, and graft type. Multiple linear regression modeling was used to evaluate whether having high-grade pre-operative laxity was associated with poorer IKDC or KOOS-QOL scores at 2 years post-operative, controlling for patient age, sex, BMI, and smoking status, baseline score, activity level, graft type, and the presence and treatment of meniscal tears. Results: Two year revision data were available for 1333 patients (95.4%) and patient-reported outcomes were available for 1205 patients (86.4%). High-grade pre-operative laxity was noted in 395 patients (29.6%), including high grade pivot-shift in 24.9%, high-grade Lachman in 11.5%, and high-grade anterior drawer in 8.1%. ACL graft revision was performed in 59 patients (4.4%). The mean post-operative IKDC score was 84.1 ± 14.4 and the mean KOOS-QOL score was 75.1 ± 20.4. The presence of high grade pre-laxity was not associated with increased odds of ACL graft revision (OR=1.47, 95% CI: 0.85 - 2.55, p = 0.17). Similarly, the presence of high-grade pre-laxity was not associated with any difference in post-operative IKDC (β = -0.33, p = 0.71) or KOOS-QOL (β = -0.51, p = 0.70). Conclusion: The presence of high-grade pre-operative knee laxity as assessed by physical examination under anesthesia (Grade 3+ pivot-shift, Lachman > 10mm, or anterior drawer greater than 10mm) is not associated increased odds of revision ACL surgery or poorer patient-reported outcome scores at 2 years following ACL reconstruction.