Clinical femoral anteversion (Craig test) and hip range of motion (ROM) have been associated with... more Clinical femoral anteversion (Craig test) and hip range of motion (ROM) have been associated with valgus collapse, but their clinical usefulness in predicting biomechanics is unknown. Our purpose was to determine the individual and combined predictive power of femoral anteversion and passive hip ROM on 3-dimensional valgus collapse (hip internal rotation and adduction, knee rotation, and abduction) during a single-leg forward landing in females. Femoral anteversion and passive hip ROM were measured on 20 females (24.9 [4.1] y, 168.7 [8.0] cm, 63.8 [11.6] kg). Three-dimensional kinematics and kinetics were collected over 5 trials of the task. Each variable was averaged across trials. Backward, stepwise regressions determined the extent to which our independent variables were associated with valgus collapse. The combination of greater hip internal and external rotation ROM (partial r = .52 and .56) predicted greater peak knee internal rotation moment (R2 = .38, P = .02). Less hip internal rotation ROM (partial r = −.44) predicted greater peak knee abduction moments (R2 = .20, P = .05). Greater total hip ROM (internal and external rotation ROM) was not consistently associated with combined motions of valgus collapse but was indicative of isolated knee moments. Passive hip ROM is more associated with knee moments than is femoral anteversion as measured with Craig test.
This chapter summarizes the findings and discussion focused on ACL risk factors, screening, and i... more This chapter summarizes the findings and discussion focused on ACL risk factors, screening, and injury prevention from the 2015 ACL Research Retreat. Risk factors include neuromuscular, anatomical, structural, genetic, and hormonal. For each risk factor, the current understandings, key unknowns, and directions for future research are described. In addition, risk factor screening and injury prevention are discussed in a similar manner. A consensus statement was devised that reflects the most recent advances in this field.
Medicine and Science in Sports and Exercise, May 1, 1999
annual meeting of the American Academy of Orthopaedic Surgeons, James Garrick and Ralph Requa pre... more annual meeting of the American Academy of Orthopaedic Surgeons, James Garrick and Ralph Requa presented a paper entitled "ACL Injuries in Women: Epidemiology." They found that, between 1965 and the present, 3514 MEDLINE citations were indexed under "anterior cruciate ligament," yet only 130 were indexed under prevention, and fewer than 10 focused on prevention of the injury. This special issue of the Journal of Athletic Training has several purposes: to remind readers that the epidemic of ACL injuries in female athletes continues, to identify potential risk factors that can be targeted for preventive interventions, and to recognize important research initiatives in our quest to reduce the incidence of this injury in both female and male athletes. In 1995, Elizabeth Arendt and Randall Dick published their seminal epidemiologic research in the American Journal of Sports Medicine demonstrating a higher rate of ACL injuries in college female soccer and basketball athletes in comparison with males participating in the same sports. In this issue, you will find a 5-year update of the NCAA epidemiologic research that reaffirms the higher rate of injury in female athletes. You will also find an epidemiologic review that documents a higher rate of ACL injury in physically active females participating at the college, high school, Olympic, and military levels. Both papers emphasize the importance of prevention as the cornerstone to reducing the incidence of ACL injury in the female athlete. To exemplify this emphasis on prevention, many of the articles in this issue focus on the potential risk factors for ACL injury. Extrinsic factors, which are somewhat controllable, include playing style, preparation and practice, conditioning, skill acquisition, environmental conditions, and equipment such as shoes and playing surface. Intrinsic factors include individual physical and psychosocial factors that are less controllable than the extrinsic factors. A plan for the standardized screening of the clinically measurable intrinsic anatomical risk factors, such as subtalar joint pronation, knee recurvatum, external tibial rotation, and lower extremity muscular strength, is presented. Several of the original research papers in this issue focus on the intrinsic risk factors of joint laxity, postural control, and knee biodynamics in female and male subjects. The general use of electromyography in assessing sex differences is explained, and 3 papers examine the neuromuscular factors related to muscle preactivity, fatigue, and reactive muscle firing during functional activity. Very recent research is presented that documents greater anterior laxity in conjunction with elevations in estrogen and progesterone levels during the menstrual cycle. Fluctuating hormonal levels represent one of the more obvious differences between males and females, yet the relevance of this finding to ACL injury in the female athlete has yet to be elucidated. Specialized rehabilitation programs for the female athlete who is ACL deficient or who has undergone ACL reconstruction are presented. These programs also have application for preinjury proprioceptive, strength, and neuromuscular control exercises for the prevention of ACL injury. Finally, you will find that the Current Literature and Abstracts sections of this issue are entirely devoted to the anterior cruciate ligament. Many people deserve recognition for this special issue. The authors and manuscript reviewers completed the process of review and revision in a timely manner so that deadlines for production could be met. The Associate Editors played a critical role in reviewing the papers in this issue, and, as always, the JAT office staff did a stellar job of overseeing and moving the manuscripts into production. I trust you will find the information in this issue useful to your clinical practice, and I hope athletic training researchers are stimulated to continue our efforts to find solutions to the increased risk of anterior cruciate ligament injury in the female athlete.
The International journal of sports physical therapy, Dec 1, 2022
Background Females have an increased incidence of musculoskeletal injuries compared to males. Sex... more Background Females have an increased incidence of musculoskeletal injuries compared to males. Sex differences in neuromuscular control has been widely studied regarding the dynamics and muscle activity during preplanned movements. While muscle activation patterns and movement biomechanics are understood to differ between sexes, it is not well understood how sex influences brain activity for lower extremity movement. Since the brain plays a vital role for voluntary movement and joint stability, it is important to understand the sex differences in brain function in order to better understand neuromuscular control associated with increased musculoskeletal injury risk in female. Hypothesis/Purpose The purpose of this study is to understand the differences in brain activation patterns between sexes during a simple active knee extension-flexion movement. It was hypothesized that females would demonstrate higher cortical activation in the somatosensory areas compared to males as a compensatory strategy. Study Design Cross-Sectional Study Methods Thirteen males and seventeen females who were healthy and physically active participated in this study (Male: 23.7±3.8 years, 74.5±13.5 kg, 172.3±6.4 cm; Female: 20.6±1.6 years, 65.4±12.8 kg, 163±6.1 cm). Functional magnetic resonance imaging data were obtained during a simple left knee extension-flexion exercise with their own leg weight while lying on the MRI table. The blood oxygen level dependent (BOLD) signals were compared between sexes. Results There was significantly greater activation in the visual cortices and premotor cortex in females compared to males during the studied movement. Males demonstrated significantly greater activation in the right cerebellum. Conclusion The results revealed sex differences in BOLD signal during simple knee extension-flexion movement. The results suggest that sex may be a biological factor in understanding brain activity associated with knee motor control.
Sports Health: A Multidisciplinary Approach, Nov 17, 2011
I njuries to the anterior cruciate ligament (ACL) of the knee are immediately disabling, take a s... more I njuries to the anterior cruciate ligament (ACL) of the knee are immediately disabling, take a significant amount of time to rehabilitate, are often associated with other concomitant articular injuries, and result in an increased risk of early onset posttraumatic osteoarthritis regardless of the treatment administered. 26 Treatment of the injury is costly and not always successful at returning patients to their preinjury activity level. Injury rates as high as 2.8 and 3.2 injuries per 10 000 athlete exposures have been reported in women's collegiate basketball and soccer. 31 Consequently, identification of factors associated with increased risk of suffering ACL injury during sport and physical activity has become a focus of musculoskeletal research. This information is needed to understand the mechanisms that produce this debilitating injury and may allow identification of those at increased risk so that targeted interventions can be implemented.
Orthopaedic Journal of Sports Medicine, Feb 1, 2021
Background: High anterior knee laxity (AKL) has been prospectively identified as a risk factor fo... more Background: High anterior knee laxity (AKL) has been prospectively identified as a risk factor for anterior cruciate ligament (ACL) injuries. Given that ACL morphometry and structural composition have the potential to influence ligamentous strength, understanding how these factors are associated with greater AKL is warranted. Hypothesis: Smaller ACL volumes combined with longer T2* relaxation times would collectively predict greater AKL.
We examined sex differences in general joint laxity (GJL), and anterior-posterior displacement (A... more We examined sex differences in general joint laxity (GJL), and anterior-posterior displacement (ANT-POST), varus-valgus rotation (VR-VL), and internal-external rotation (INT-EXT) knee laxities, and determined whether greater ANT and GJL predicted greater VR-VL and INT-EXT. Twenty subjects were measured for GJL, and scored on a scale of 0-9. ANT and POST were measured using a standard knee arthrometer at 133 N. VR-VL and INT-EXT were measured using a custom joint laxity testing device, defined as the angular displacements (deg) of the tibia relative to the femur produced by 0-10 Nm of varus-valgus torques, and 0-5 Nm of internalexternal torques, respectively. INT-EXT were measured during both non-weight-bearing (NWB) and weight-bearing (WB = 40% body weight) conditions while VR-VL were measured NWB. All laxity measures were greater for females compared to males except for POST. ANT and GJL positively predicted 62.5% of the variance in VR-VL and 41.8% of the variance in WB INT-EXT. ANT was the sole predictor of INT-EXT in NWB, explaining 42.3% of the variance. These findings suggest that subjects who score higher on clinical measures of GJL and ANT are also likely to have greater VR-VL and INT-EXT knee laxities.
Carolina Digital Repository (University of North Carolina at Chapel Hill), 2013
Context: Greater sagittal-plane energy absorption (EA) during the initial impact phase (INI) of l... more Context: Greater sagittal-plane energy absorption (EA) during the initial impact phase (INI) of landing is consistent with sagittal-plane biomechanics that likely increase anterior cruciate ligament (ACL) loading, but it does not appear to influence frontal-plane biomechanics. We do not know whether frontalplane INI EA is related to high-risk frontal-plane biomechanics. Objective: To compare biomechanics among INI EA groups, determine if women are represented more in the high group, and evaluate interplanar INI EA relationships. Design: Descriptive laboratory study. Setting: Research laboratory. Patients or Other Participants: Participants included 82 (41 men, 41 women; age ¼ 21.0 6 2.4 years, height ¼ 1.74 6 0.10 m, mass ¼ 70.3 6 16.1 kg) healthy, physically active volunteers. Intervention(s): We assessed landing biomechanics with an electromagnetic motion-capture system and force plate. Main Outcome Measure(s): We calculated frontal-and sagittal-plane total, hip, knee, and ankle INI EA. Total frontalplane INI EA was used to create high, moderate, and low tertiles. Frontal-plane knee and hip kinematics, peak vertical and posterior ground reaction forces, and peak internal knee-varus moment (pKVM) were identified and compared across groups using 1-way analyses of variance. We used a v 2 analysis to evaluate male and female allocation to INI EA groups. We used simple, bivariate Pearson product moment correlations to assess interplanar INI EA relationships. Results: The high-INI EA group exhibited greater knee valgus at ground contact, hip adduction at pKVM, and peak hip adduction than the low-INI EA group (P , .05) and greater peak knee valgus, pKVM, and knee valgus at pKVM than the moderate-(P , .05) and low-(P , .05) INI EA groups. Women were more likely than men to be in the high-INI EA group (v 2 ¼ 4.909, P ¼ .03). Sagittal-plane knee and frontal-plane hip INI EA (r ¼ 0.301, P ¼ .006) and sagittal-plane and frontal-plane ankle INI EA were associated (r ¼ 0.224, P ¼ .04). No other interplanar INI EA relationships were found (P. .05). Conclusions: Greater frontal-plane INI EA was associated with less favorable frontal-plane biomechanics that likely result in greater ACL loading. Women were more likely than men to use greater frontal-plane INI EA. The magnitudes of sagittal-and frontal-plane INI EA were largely independent.
Objective: To provide certified athletic trainers, physicians, and other health care and fitness ... more Objective: To provide certified athletic trainers, physicians, and other health care and fitness professionals with recommendations based on current evidence regarding the prevention of noncontact and indirect-contact anterior cruciate ligament (ACL) injuries in athletes and physically active individuals. Background: Preventing ACL injuries during sport and physical activity may dramatically decrease medical costs and long-term disability. Implementing ACL injury-prevention training programs may improve an individual's neuromuscular control and lower extremity biomechanics and thereby reduce the risk of injury. Recent evidence indicates that ACL injuries may be prevented through the use of multicomponent neuromusculartraining programs. Recommendations: Multicomponent injury-prevention training programs are recommended for reducing noncontact and indirect-contact ACL injuries and strongly recommended for reducing noncontact and indirect-contact knee injuries during physical activity. These programs are advocated for improving balance, lower extremity biomechanics, muscle activation, functional performance, strength, and power, as well as decreasing landing impact forces. A multicomponent injury-prevention training program should, at minimum, provide feedback on movement technique in at least 3 of the following exercise categories: strength, plyometrics, agility, balance, and flexibility. Further guidance on training dosage, intensity, and implementation recommendations is offered in this statement.
Context: Females have consistently higher anterior cruciate ligament (ACL) injury rates than male... more Context: Females have consistently higher anterior cruciate ligament (ACL) injury rates than males. The reasons for this disparity are not fully understood. Whereas ACL morphometric characteristics are associated with injury risk and females have a smaller absolute ACL size, comprehensive sex comparisons that adequately account for sex differences in body mass index (BMI) have been limited. Objective: To investigate sex differences among in vivo ACL morphometric measures before and after controlling for femoral notch width and BMI. Design: Cross-sectional study. Setting: Laboratory. Patients or Other Participants: Twenty recreationally active men (age ¼ 23.2 6 2.9 years, height ¼ 180.4 6 6.7 cm, mass ¼ 84.0 6 10.9 kg) and 20 recreationally active women (age ¼ 21.3 6 2.3 years, height ¼ 166.9 6 7.7 cm, mass ¼ 61.9 6 7.2 kg) participated. Main Outcome Measure(s): Structural magnetic resonance imaging sequences were performed on the left knee. Anterior cruciate ligament volume, width, and cross-sectional area measures were obtained from T2-weighted images and normalized to femoral notch width and BMI. Femoral notch width was measured from T1-weighted images. We used independentsamples t tests to examine sex differences in absolute and normalized measures.
Sports Health: A Multidisciplinary Approach, Sep 13, 2012
Background: Hip strength is associated with numerous orthopaedic and neuromuscular injuries and/o... more Background: Hip strength is associated with numerous orthopaedic and neuromuscular injuries and/or pathologies and may be assessed with a variety of anatomic testing positions and techniques. Isokinetic dynamometers are generally too cumbersome and intricate for efficient use in mass screenings (for prognostic studies of risk for injury) as well as with special populations. The reliability of isometric testing devices has demonstrated varied reliability, generally examining only 1 or 2 motions of the hip and reporting values of force, not torque. Consequently, there is a need for an efficient hip strengthtesting device to quantify torque that tests subjects in 1 anatomic position, while evaluating multiple hip motions. Hypothesis: Evaluation of supine hip abduction, adduction, flexion, and extension torque using a new stabilized dynamometer system will produce good to excellent intra-and interexaminer reliability results. Study Design: A blinded, randomized, repeated-measures study design was used in this descriptive laboratory investigation. Methods: Supine isometric hip flexion, extension, abduction, and adduction torques were evaluated with a cage-stabilized dynamometer in 19 collegiate and professional-level ice hockey athletes by 2 investigators at 3 time intervals. Inter-and intrarater reliability was assessed. Results: Supine hip flexion, extension, abduction, and adduction torque was performed with good to excellent inter-and intrarater reliability (intraclass correlation coefficients ranging from 0.74 to 0.92 and 0.78 to 0.92, respectively) for all motions tested. Conclusions: We have developed an isometric hip strength-testing device that can be assembled around an examination table to efficiently and reliably evaluate torque developed for multiple motions of the hip. Clinical Relevance: This device and testing protocol may be used to efficiently evaluate hip strength in numerous settings; it allows decreased subject burden and increased comfort (which may be important following an injury in case-control investigations); and it may be well tolerated when testing athletes as well as special populations in the clinical setting.
Carolina Digital Repository (University of North Carolina at Chapel Hill), 2013
Context: Eccentric muscle actions of the lower extremity absorb kinetic energy during landing. Gr... more Context: Eccentric muscle actions of the lower extremity absorb kinetic energy during landing. Greater total sagittal-plane energy absorption (EA) during the initial impact phase (INI) of landing has been associated with landing biomechanics considered high risk for anterior cruciate ligament (ACL) injury. We do not know whether groups with different INI EA magnitudes exhibit meaningful differences in ACL-related landing biomechanics and whether INI EA might be useful to identify ACL injury-risk potential. Objective: To compare biomechanical factors associated with noncontact ACL injury among sagittal-plane INI EA groups and to determine whether an association exists between sex and sagittal-plane INI EA group assignment to evaluate the face validity of using sagittal-plane INI EA to identify ACL injury risk. Design: Descriptive laboratory study. Setting: Research laboratory. Patients or Other Participants: A total of 82 (41 men, 41 women; age ¼ 21.0 6 2.4 years, height ¼ 1.74 6 0.10 m, mass ¼ 70.3 6 16.1 kg) healthy, physically active individuals volunteered. Intervention(s): We assessed landing biomechanics using an electromagnetic motion-capture system and force plate during a double-legged jump-landing task. Main Outcome Measure(s): Total INI EA was used to group participants into high, moderate, and low tertiles. Sagittal-and frontal-plane knee kinematics; peak vertical and posterior ground reaction forces (GRFs); anterior tibial shear force; and internal hip extension, knee extension, and knee varus moments were identified and compared across groups using 1-way analyses of variance. We used a v 2 analysis to compare male and female representation in the high and low groups. Results: The high group exhibited greater knee-extension moment and posterior GRFs than both the moderate (P , .05) and low (P , .05) groups and greater anterior tibial shear force than the low group (P , .05). No other group differences were noted. Women were not represented more than men in the high group (v 2 ¼ 1.20, P ¼ .27). Conclusions: Greater sagittal-plane INI EA likely indicates greater ACL loading, but it does not appear to influence frontalplane biomechanics related to ACL injury. Women were not more likely than men to demonstrate greater INI EA, suggesting that quantification of sagittal-plane INI EA alone is not sufficient to infer ACL injury-risk potential.
Clinical femoral anteversion (Craig test) and hip range of motion (ROM) have been associated with... more Clinical femoral anteversion (Craig test) and hip range of motion (ROM) have been associated with valgus collapse, but their clinical usefulness in predicting biomechanics is unknown. Our purpose was to determine the individual and combined predictive power of femoral anteversion and passive hip ROM on 3-dimensional valgus collapse (hip internal rotation and adduction, knee rotation, and abduction) during a single-leg forward landing in females. Femoral anteversion and passive hip ROM were measured on 20 females (24.9 [4.1] y, 168.7 [8.0] cm, 63.8 [11.6] kg). Three-dimensional kinematics and kinetics were collected over 5 trials of the task. Each variable was averaged across trials. Backward, stepwise regressions determined the extent to which our independent variables were associated with valgus collapse. The combination of greater hip internal and external rotation ROM (partial r = .52 and .56) predicted greater peak knee internal rotation moment (R2 = .38, P = .02). Less hip internal rotation ROM (partial r = −.44) predicted greater peak knee abduction moments (R2 = .20, P = .05). Greater total hip ROM (internal and external rotation ROM) was not consistently associated with combined motions of valgus collapse but was indicative of isolated knee moments. Passive hip ROM is more associated with knee moments than is femoral anteversion as measured with Craig test.
This chapter summarizes the findings and discussion focused on ACL risk factors, screening, and i... more This chapter summarizes the findings and discussion focused on ACL risk factors, screening, and injury prevention from the 2015 ACL Research Retreat. Risk factors include neuromuscular, anatomical, structural, genetic, and hormonal. For each risk factor, the current understandings, key unknowns, and directions for future research are described. In addition, risk factor screening and injury prevention are discussed in a similar manner. A consensus statement was devised that reflects the most recent advances in this field.
Medicine and Science in Sports and Exercise, May 1, 1999
annual meeting of the American Academy of Orthopaedic Surgeons, James Garrick and Ralph Requa pre... more annual meeting of the American Academy of Orthopaedic Surgeons, James Garrick and Ralph Requa presented a paper entitled "ACL Injuries in Women: Epidemiology." They found that, between 1965 and the present, 3514 MEDLINE citations were indexed under "anterior cruciate ligament," yet only 130 were indexed under prevention, and fewer than 10 focused on prevention of the injury. This special issue of the Journal of Athletic Training has several purposes: to remind readers that the epidemic of ACL injuries in female athletes continues, to identify potential risk factors that can be targeted for preventive interventions, and to recognize important research initiatives in our quest to reduce the incidence of this injury in both female and male athletes. In 1995, Elizabeth Arendt and Randall Dick published their seminal epidemiologic research in the American Journal of Sports Medicine demonstrating a higher rate of ACL injuries in college female soccer and basketball athletes in comparison with males participating in the same sports. In this issue, you will find a 5-year update of the NCAA epidemiologic research that reaffirms the higher rate of injury in female athletes. You will also find an epidemiologic review that documents a higher rate of ACL injury in physically active females participating at the college, high school, Olympic, and military levels. Both papers emphasize the importance of prevention as the cornerstone to reducing the incidence of ACL injury in the female athlete. To exemplify this emphasis on prevention, many of the articles in this issue focus on the potential risk factors for ACL injury. Extrinsic factors, which are somewhat controllable, include playing style, preparation and practice, conditioning, skill acquisition, environmental conditions, and equipment such as shoes and playing surface. Intrinsic factors include individual physical and psychosocial factors that are less controllable than the extrinsic factors. A plan for the standardized screening of the clinically measurable intrinsic anatomical risk factors, such as subtalar joint pronation, knee recurvatum, external tibial rotation, and lower extremity muscular strength, is presented. Several of the original research papers in this issue focus on the intrinsic risk factors of joint laxity, postural control, and knee biodynamics in female and male subjects. The general use of electromyography in assessing sex differences is explained, and 3 papers examine the neuromuscular factors related to muscle preactivity, fatigue, and reactive muscle firing during functional activity. Very recent research is presented that documents greater anterior laxity in conjunction with elevations in estrogen and progesterone levels during the menstrual cycle. Fluctuating hormonal levels represent one of the more obvious differences between males and females, yet the relevance of this finding to ACL injury in the female athlete has yet to be elucidated. Specialized rehabilitation programs for the female athlete who is ACL deficient or who has undergone ACL reconstruction are presented. These programs also have application for preinjury proprioceptive, strength, and neuromuscular control exercises for the prevention of ACL injury. Finally, you will find that the Current Literature and Abstracts sections of this issue are entirely devoted to the anterior cruciate ligament. Many people deserve recognition for this special issue. The authors and manuscript reviewers completed the process of review and revision in a timely manner so that deadlines for production could be met. The Associate Editors played a critical role in reviewing the papers in this issue, and, as always, the JAT office staff did a stellar job of overseeing and moving the manuscripts into production. I trust you will find the information in this issue useful to your clinical practice, and I hope athletic training researchers are stimulated to continue our efforts to find solutions to the increased risk of anterior cruciate ligament injury in the female athlete.
The International journal of sports physical therapy, Dec 1, 2022
Background Females have an increased incidence of musculoskeletal injuries compared to males. Sex... more Background Females have an increased incidence of musculoskeletal injuries compared to males. Sex differences in neuromuscular control has been widely studied regarding the dynamics and muscle activity during preplanned movements. While muscle activation patterns and movement biomechanics are understood to differ between sexes, it is not well understood how sex influences brain activity for lower extremity movement. Since the brain plays a vital role for voluntary movement and joint stability, it is important to understand the sex differences in brain function in order to better understand neuromuscular control associated with increased musculoskeletal injury risk in female. Hypothesis/Purpose The purpose of this study is to understand the differences in brain activation patterns between sexes during a simple active knee extension-flexion movement. It was hypothesized that females would demonstrate higher cortical activation in the somatosensory areas compared to males as a compensatory strategy. Study Design Cross-Sectional Study Methods Thirteen males and seventeen females who were healthy and physically active participated in this study (Male: 23.7±3.8 years, 74.5±13.5 kg, 172.3±6.4 cm; Female: 20.6±1.6 years, 65.4±12.8 kg, 163±6.1 cm). Functional magnetic resonance imaging data were obtained during a simple left knee extension-flexion exercise with their own leg weight while lying on the MRI table. The blood oxygen level dependent (BOLD) signals were compared between sexes. Results There was significantly greater activation in the visual cortices and premotor cortex in females compared to males during the studied movement. Males demonstrated significantly greater activation in the right cerebellum. Conclusion The results revealed sex differences in BOLD signal during simple knee extension-flexion movement. The results suggest that sex may be a biological factor in understanding brain activity associated with knee motor control.
Sports Health: A Multidisciplinary Approach, Nov 17, 2011
I njuries to the anterior cruciate ligament (ACL) of the knee are immediately disabling, take a s... more I njuries to the anterior cruciate ligament (ACL) of the knee are immediately disabling, take a significant amount of time to rehabilitate, are often associated with other concomitant articular injuries, and result in an increased risk of early onset posttraumatic osteoarthritis regardless of the treatment administered. 26 Treatment of the injury is costly and not always successful at returning patients to their preinjury activity level. Injury rates as high as 2.8 and 3.2 injuries per 10 000 athlete exposures have been reported in women's collegiate basketball and soccer. 31 Consequently, identification of factors associated with increased risk of suffering ACL injury during sport and physical activity has become a focus of musculoskeletal research. This information is needed to understand the mechanisms that produce this debilitating injury and may allow identification of those at increased risk so that targeted interventions can be implemented.
Orthopaedic Journal of Sports Medicine, Feb 1, 2021
Background: High anterior knee laxity (AKL) has been prospectively identified as a risk factor fo... more Background: High anterior knee laxity (AKL) has been prospectively identified as a risk factor for anterior cruciate ligament (ACL) injuries. Given that ACL morphometry and structural composition have the potential to influence ligamentous strength, understanding how these factors are associated with greater AKL is warranted. Hypothesis: Smaller ACL volumes combined with longer T2* relaxation times would collectively predict greater AKL.
We examined sex differences in general joint laxity (GJL), and anterior-posterior displacement (A... more We examined sex differences in general joint laxity (GJL), and anterior-posterior displacement (ANT-POST), varus-valgus rotation (VR-VL), and internal-external rotation (INT-EXT) knee laxities, and determined whether greater ANT and GJL predicted greater VR-VL and INT-EXT. Twenty subjects were measured for GJL, and scored on a scale of 0-9. ANT and POST were measured using a standard knee arthrometer at 133 N. VR-VL and INT-EXT were measured using a custom joint laxity testing device, defined as the angular displacements (deg) of the tibia relative to the femur produced by 0-10 Nm of varus-valgus torques, and 0-5 Nm of internalexternal torques, respectively. INT-EXT were measured during both non-weight-bearing (NWB) and weight-bearing (WB = 40% body weight) conditions while VR-VL were measured NWB. All laxity measures were greater for females compared to males except for POST. ANT and GJL positively predicted 62.5% of the variance in VR-VL and 41.8% of the variance in WB INT-EXT. ANT was the sole predictor of INT-EXT in NWB, explaining 42.3% of the variance. These findings suggest that subjects who score higher on clinical measures of GJL and ANT are also likely to have greater VR-VL and INT-EXT knee laxities.
Carolina Digital Repository (University of North Carolina at Chapel Hill), 2013
Context: Greater sagittal-plane energy absorption (EA) during the initial impact phase (INI) of l... more Context: Greater sagittal-plane energy absorption (EA) during the initial impact phase (INI) of landing is consistent with sagittal-plane biomechanics that likely increase anterior cruciate ligament (ACL) loading, but it does not appear to influence frontal-plane biomechanics. We do not know whether frontalplane INI EA is related to high-risk frontal-plane biomechanics. Objective: To compare biomechanics among INI EA groups, determine if women are represented more in the high group, and evaluate interplanar INI EA relationships. Design: Descriptive laboratory study. Setting: Research laboratory. Patients or Other Participants: Participants included 82 (41 men, 41 women; age ¼ 21.0 6 2.4 years, height ¼ 1.74 6 0.10 m, mass ¼ 70.3 6 16.1 kg) healthy, physically active volunteers. Intervention(s): We assessed landing biomechanics with an electromagnetic motion-capture system and force plate. Main Outcome Measure(s): We calculated frontal-and sagittal-plane total, hip, knee, and ankle INI EA. Total frontalplane INI EA was used to create high, moderate, and low tertiles. Frontal-plane knee and hip kinematics, peak vertical and posterior ground reaction forces, and peak internal knee-varus moment (pKVM) were identified and compared across groups using 1-way analyses of variance. We used a v 2 analysis to evaluate male and female allocation to INI EA groups. We used simple, bivariate Pearson product moment correlations to assess interplanar INI EA relationships. Results: The high-INI EA group exhibited greater knee valgus at ground contact, hip adduction at pKVM, and peak hip adduction than the low-INI EA group (P , .05) and greater peak knee valgus, pKVM, and knee valgus at pKVM than the moderate-(P , .05) and low-(P , .05) INI EA groups. Women were more likely than men to be in the high-INI EA group (v 2 ¼ 4.909, P ¼ .03). Sagittal-plane knee and frontal-plane hip INI EA (r ¼ 0.301, P ¼ .006) and sagittal-plane and frontal-plane ankle INI EA were associated (r ¼ 0.224, P ¼ .04). No other interplanar INI EA relationships were found (P. .05). Conclusions: Greater frontal-plane INI EA was associated with less favorable frontal-plane biomechanics that likely result in greater ACL loading. Women were more likely than men to use greater frontal-plane INI EA. The magnitudes of sagittal-and frontal-plane INI EA were largely independent.
Objective: To provide certified athletic trainers, physicians, and other health care and fitness ... more Objective: To provide certified athletic trainers, physicians, and other health care and fitness professionals with recommendations based on current evidence regarding the prevention of noncontact and indirect-contact anterior cruciate ligament (ACL) injuries in athletes and physically active individuals. Background: Preventing ACL injuries during sport and physical activity may dramatically decrease medical costs and long-term disability. Implementing ACL injury-prevention training programs may improve an individual's neuromuscular control and lower extremity biomechanics and thereby reduce the risk of injury. Recent evidence indicates that ACL injuries may be prevented through the use of multicomponent neuromusculartraining programs. Recommendations: Multicomponent injury-prevention training programs are recommended for reducing noncontact and indirect-contact ACL injuries and strongly recommended for reducing noncontact and indirect-contact knee injuries during physical activity. These programs are advocated for improving balance, lower extremity biomechanics, muscle activation, functional performance, strength, and power, as well as decreasing landing impact forces. A multicomponent injury-prevention training program should, at minimum, provide feedback on movement technique in at least 3 of the following exercise categories: strength, plyometrics, agility, balance, and flexibility. Further guidance on training dosage, intensity, and implementation recommendations is offered in this statement.
Context: Females have consistently higher anterior cruciate ligament (ACL) injury rates than male... more Context: Females have consistently higher anterior cruciate ligament (ACL) injury rates than males. The reasons for this disparity are not fully understood. Whereas ACL morphometric characteristics are associated with injury risk and females have a smaller absolute ACL size, comprehensive sex comparisons that adequately account for sex differences in body mass index (BMI) have been limited. Objective: To investigate sex differences among in vivo ACL morphometric measures before and after controlling for femoral notch width and BMI. Design: Cross-sectional study. Setting: Laboratory. Patients or Other Participants: Twenty recreationally active men (age ¼ 23.2 6 2.9 years, height ¼ 180.4 6 6.7 cm, mass ¼ 84.0 6 10.9 kg) and 20 recreationally active women (age ¼ 21.3 6 2.3 years, height ¼ 166.9 6 7.7 cm, mass ¼ 61.9 6 7.2 kg) participated. Main Outcome Measure(s): Structural magnetic resonance imaging sequences were performed on the left knee. Anterior cruciate ligament volume, width, and cross-sectional area measures were obtained from T2-weighted images and normalized to femoral notch width and BMI. Femoral notch width was measured from T1-weighted images. We used independentsamples t tests to examine sex differences in absolute and normalized measures.
Sports Health: A Multidisciplinary Approach, Sep 13, 2012
Background: Hip strength is associated with numerous orthopaedic and neuromuscular injuries and/o... more Background: Hip strength is associated with numerous orthopaedic and neuromuscular injuries and/or pathologies and may be assessed with a variety of anatomic testing positions and techniques. Isokinetic dynamometers are generally too cumbersome and intricate for efficient use in mass screenings (for prognostic studies of risk for injury) as well as with special populations. The reliability of isometric testing devices has demonstrated varied reliability, generally examining only 1 or 2 motions of the hip and reporting values of force, not torque. Consequently, there is a need for an efficient hip strengthtesting device to quantify torque that tests subjects in 1 anatomic position, while evaluating multiple hip motions. Hypothesis: Evaluation of supine hip abduction, adduction, flexion, and extension torque using a new stabilized dynamometer system will produce good to excellent intra-and interexaminer reliability results. Study Design: A blinded, randomized, repeated-measures study design was used in this descriptive laboratory investigation. Methods: Supine isometric hip flexion, extension, abduction, and adduction torques were evaluated with a cage-stabilized dynamometer in 19 collegiate and professional-level ice hockey athletes by 2 investigators at 3 time intervals. Inter-and intrarater reliability was assessed. Results: Supine hip flexion, extension, abduction, and adduction torque was performed with good to excellent inter-and intrarater reliability (intraclass correlation coefficients ranging from 0.74 to 0.92 and 0.78 to 0.92, respectively) for all motions tested. Conclusions: We have developed an isometric hip strength-testing device that can be assembled around an examination table to efficiently and reliably evaluate torque developed for multiple motions of the hip. Clinical Relevance: This device and testing protocol may be used to efficiently evaluate hip strength in numerous settings; it allows decreased subject burden and increased comfort (which may be important following an injury in case-control investigations); and it may be well tolerated when testing athletes as well as special populations in the clinical setting.
Carolina Digital Repository (University of North Carolina at Chapel Hill), 2013
Context: Eccentric muscle actions of the lower extremity absorb kinetic energy during landing. Gr... more Context: Eccentric muscle actions of the lower extremity absorb kinetic energy during landing. Greater total sagittal-plane energy absorption (EA) during the initial impact phase (INI) of landing has been associated with landing biomechanics considered high risk for anterior cruciate ligament (ACL) injury. We do not know whether groups with different INI EA magnitudes exhibit meaningful differences in ACL-related landing biomechanics and whether INI EA might be useful to identify ACL injury-risk potential. Objective: To compare biomechanical factors associated with noncontact ACL injury among sagittal-plane INI EA groups and to determine whether an association exists between sex and sagittal-plane INI EA group assignment to evaluate the face validity of using sagittal-plane INI EA to identify ACL injury risk. Design: Descriptive laboratory study. Setting: Research laboratory. Patients or Other Participants: A total of 82 (41 men, 41 women; age ¼ 21.0 6 2.4 years, height ¼ 1.74 6 0.10 m, mass ¼ 70.3 6 16.1 kg) healthy, physically active individuals volunteered. Intervention(s): We assessed landing biomechanics using an electromagnetic motion-capture system and force plate during a double-legged jump-landing task. Main Outcome Measure(s): Total INI EA was used to group participants into high, moderate, and low tertiles. Sagittal-and frontal-plane knee kinematics; peak vertical and posterior ground reaction forces (GRFs); anterior tibial shear force; and internal hip extension, knee extension, and knee varus moments were identified and compared across groups using 1-way analyses of variance. We used a v 2 analysis to compare male and female representation in the high and low groups. Results: The high group exhibited greater knee-extension moment and posterior GRFs than both the moderate (P , .05) and low (P , .05) groups and greater anterior tibial shear force than the low group (P , .05). No other group differences were noted. Women were not represented more than men in the high group (v 2 ¼ 1.20, P ¼ .27). Conclusions: Greater sagittal-plane INI EA likely indicates greater ACL loading, but it does not appear to influence frontalplane biomechanics related to ACL injury. Women were not more likely than men to demonstrate greater INI EA, suggesting that quantification of sagittal-plane INI EA alone is not sufficient to infer ACL injury-risk potential.
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Papers by Sandra Shultz