Dynamic valgus alignment and functional strength in males and females during maturation

Patellofemoral pain and musculoskeletal features in young pre- and post-pubertal female dancers

The aim of this study was to examine associations between patellofemoral pain (PFP) and musculoskeletal features (such as tendon structure and bone properties) in young (pre- and post-pubertal) female dancers. A total of 49 dancers participated in this study (mean age 13.6 ± 2.9; weight 47.0 ± 13.2; height 153.7 ± 12.9 and body mass index (BMI) 19.4 ± 3.1) and were assessed for the following factors: dance background and Tanner stage through interviews; ultrasonography assessments of bone properties and patellar tendon structure through ultrasonographic tissue characterization and quantitative ultrasound, respectively; and anthropometric measurements, muscle strength, range of motion (ROM), hypermobility and PFP through physical examinations. PFP was found in 49% of the participants. Post-pubertal dancers with no-PFP were found to have greater muscle strength, greater radial and tibial properties, and better tendon structure compared to pre-pubertal dancers with PFP and compared to pre-pubertal dancers with no-PFP [F(2, 41) = 18.64, p < .001; F(2, 41) = 20.46, p < .001; F(2, 41) = 33.06, p < .001; and, F(2, 41) = 6.02, p = .007, respectively]. Logistic regression showed that tibial bone properties and range of movement (ROM) in hip external rotation were significantly associated with PFP [odds ratio (OR) = .889 and OR = 2.653, respectively; Cox & Snell R2 = .701]. The study revealed a high prevalence of PFP among young dancers, with low bone properties and hyperjoint ROM emerging as the main factors that are related to PFP. These findings should be addressed by medical teams, athletic trainers, and dance teachers regarding the need for implementing modifications to dance training programmes and injury-prevention strategies in young pre-pubertal dancers.

Changes in Lower Limb Biomechanics Across Various Stages of Maturation and Implications for ACL Injury Risk in Female Athletes: a Systematic Review

BACKGROUND

Female athletes are four to six times more likely to sustain an anterior cruciate ligament (ACL) injury than male athletes. Jump-landing biomechanics are influenced by maturation, with post-pubertal female athletes at a heightened risk of ACL injuries.

OBJECTIVE

The aim of our systematic review was to identify and summarise the current evidence regarding the changes in kinematic and kinetic risk factors associated with ACL injuries during jump-landing tasks in female athletes at various stages of maturity.

METHODS

A systematic search was conducted in PubMed, CINAHL, Web of Science, SPORTDiscus, EMBASE and Scopus. Articles were included if they: (1) conducted the research on uninjured female athletes with no restriction on playing level/experience; (2) provided information regarding the stage of the maturity and the scale used for estimating the maturity status of the participants; and (3) reported a biomechanical risk factor associated with ACL injuries during jump-landing tasks across at least two different maturity groups (e.g. pre-pubertal vs post-pubertal).

RESULTS

Sixteen articles involving 2323 female athletes were included in our review. A total of 12 kinematic and 8 kinetic variables were identified across these studies. Of the 12 kinematic variables reported in our review, we found strong evidence for higher peak knee abduction angle in post-pubertal female individuals compared with pre-pubertal girls (p < 0.05). With regard to the 8 kinetic variables, we found strong evidence for lower relative peak vertical ground reaction force, higher external knee abduction moment and internal rotation moment in post-pubertal compared with pre-pubertal athletes. The strength of evidence for the remaining kinematic and kinetic variables ranged from conflicting to moderate and, in some instances, could not be determined.

CONCLUSIONS

Our study provides an overview of the changes in biomechanical risk factors in female athletes during jump-landing tasks at various stages of maturity. We found moderate-to-limited evidence for most kinematic and kinetic variables, highlighting the need for further research.

The Significance of Maximal Squat Strength for Neuromuscular Knee Control in Elite Handball Players: A Cross-Sectional Study

Both weak muscle strength and impaired neuromuscular control has previous been suggested as risk factors for future traumatic knee injury. However, data on the relationship between these two factors are scarce. Thus, the aim of this study was to investigate the relationship and influence of the one repetition maximum (1RM) barbell squat strength on dynamic knee valgus in elite female and male handball players. In this cross-sectional study 22 elite handball players (7 females) were included. A unilateral drop jump (VDJ) test was used for the assessment of frontal plane dynamic knee valgus. Players also performed a one repetition maximum (1RM) barbell squat test, expressed relative to bodyweight (r1RM), to assess maximal strength, which were dichotomized to analyze 'weak' versus 'strong' players according to median. Correlations were noted between r1RM in squat and knee valgus angle for both the non-dominant (r = -0.54; p = 0.009) and dominant leg (r = -0.46, p = 0.03). The odds of knee valgus were eight times higher, for the dominant leg, in the weak group compared to the strong group (p = 0.03) and 27 times higher, for the non-dominant leg (p = 0.002). The outcome of the present study suggests that maximum squat strength plays an important role when it comes to neuromuscular control of the knee, and that weak handball players are at higher risk of knee valgus compared to strong players during jumping activity.

Comparison of postural sway in individuals with and without dynamic knee valgus

BACKGROUND

Dynamic knee valgus (DKV) is a multi-planar faulty movement pattern that can cause faulty postural control. The primary objective of this study is to investigate the differences in postural sway (PS) between individuals aged 18-30 years old diagnosed with and without DKV.

METHODS

In this cross-sectional study, 62 students (39 males and 23 females) with and without DKV (age: 24.58 ± 2.63 years) were selected and assigned to two groups by conducting the single-leg squat test in the screening stage. The Biodex balance system was then employed to compare the two groups in PS. Mann-Whitney U test was conducted to compare the groups in PS (p ≤ 0.05).

RESULTS

The study's findings indicate that individuals with DKV did not exhibit any significant differences, compared to those without, about the anterior-posterior stability index (with p values for both static and dynamic situations at 0.309 and 0.198, respectively), medial-lateral stability index (with p values for both static and dynamic situations at 0.883 and 0.500, respectively), and overall stability index (with p values for both static and dynamic situations at 0.277 and 0.086, respectively).

CONCLUSION

Though several possible factors could contribute to the lack of significant differences in postural sway between individuals with and without DKV, such as measurement tool differences, variable sensitivity in postural stability tests, and differences in movement variability and test stance, we recommend analyzing postural sway in more functional tasks and with different methodological patterns in future studies. Such research could help develop targeted interventions for individuals with DKV and offer a better understanding of the relationship between postural control and DKV.

Dynamic knee valgus prevalence in children and its association with pain intensity, foot mobility, and sex- A cross-sectional study

Introduction

Knee pain can impact the performance of activities and sports participation in children. Dynamic knee valgus is a movement pattern commonly related to health conditions that may be associated with sex and foot kinematics in children.

Objective

To assess the prevalence of dynamic knee valgus and its relationship with foot mobility, sex, and knee pain in children.

Method

A cross-sectional observational study was carried out with 144 children (10-18 years old). The pain level was investigated using the Visual Analog Pain Scale and categorized into no pain/minor pain (≤2 cm), moderate pain (3-4,9 cm), and severe pain (≥5.0 cm). Foot mobility was assessed using the adapted navicular drop test and categorized into poor/adequate foot mobility (0.0 cm-0.9 cm) and greater foot mobility (≥1.0 cm). The dynamic knee valgus presence was checked using the step-down test. The association analysis was performed using simple tabulation considering the cluster effect. The Prevalence Ratios and the respective confidence intervals (95%) were estimated from Multiple Poisson Regression with robust variance. A significance level of 5% was adopted.

Results

The dynamic knee valgus prevalence was 26.3% and 26.9% in the right and left lower limbs, respectively. Females presented greater dynamic knee valgus frequency in the left lower limb than males. The dynamic knee valgus presence in males was associated with foot mobility in right (p = 0.001) (Prevalence Ratio: 9.33 Confidence Interval: 2.93-29.72) and left lower limbs (p = 0.003) (Prevalence Ratio: 6.25 Confidence Interval: 1.7-22.62).

Conclusion

Male and female children showed different relationships of the analyzed factors, suggesting that characteristics related to sex may impact the aspects linked to dynamic knee in children.

Sex-Specific Changes in Physical Risk Factors for Anterior Cruciate Ligament Injury by Chronological Age and Stages of Growth and Maturation From 8 to 18 Years of Age

OBJECTIVE

To critically assess the literature focused on sex-specific trajectories in physical characteristics associated with anterior cruciate ligament (ACL) injury risk by age and maturational stage.

DATA SOURCES

PubMed, CINAHL, Scopus, and SPORTDiscus databases were searched through December 2021.

STUDY SELECTION

Longitudinal and cross-sectional studies of healthy 8- to 18-year-olds, stratified by sex and age or maturation on ≥1 measure of body composition, lower extremity strength, ACL size, joint laxity, knee-joint geometry, lower extremity alignment, balance, or lower extremity biomechanics were included.

DATA EXTRACTION

Extracted data included study design, participant characteristics, maturational metrics, and outcome measures. We used random-effects meta-analyses to examine sex differences in trajectory over time. For each variable, standardized differences in means between sexes were calculated.

DATA SYNTHESIS

The search yielded 216 primary and 22 secondary articles. Less fat-free mass, leg strength, and power and greater general joint laxity were evident in girls by 8 to 10 years of age and Tanner stage I. Sex differences in body composition, strength, power, general joint laxity, and balance were more evident by 11 to 13 years of age and when transitioning from the prepubertal to pubertal stages. Sex differences in ACL size (smaller in girls), anterior knee laxity and tibiofemoral angle (greater in girls), and higher-risk biomechanics (in girls) were observed at later ages and when transitioning from the pubertal to postpubertal stages. Inconsistent study designs and data reporting limited the number of included studies.

CONCLUSIONS

Critical gaps remain in our knowledge and highlight the need to improve our understanding of the relative timing and tempo of ACL risk factor development.

Lower extremity kinematic coupling during single and double leg landing and gait in female junior athletes with dynamic knee valgus

BACKGROUND

Dynamic knee valgus (DKV) is a common lower extremity movement disorder among females. This study aimed to investigate kinematic couplings between lower extremity joints in female junior athletes with DKV during single and double-leg landing and gait.

METHODS

Twenty-six physically active female junior athletes (10-14 years old) with DKV were recruited. Kinematic couplings between rearfoot, tibia, knee, and hip were extracted using eight Vicon motion capture cameras and two force plates. Zero-lag cross-correlation coefficient and vector coding were used to calculate kinematic couplings between joints during physical tasks. Paired t-test and Wilcoxon tests were run to find significant couplings between joint motions and coupling strengths. Bonferroni posthoc was used to determine significance with α ≤ 0.05.

RESULTS

The results showed that the strongest kinematic relationship existed between rearfoot eversion/inversion and tibial internal/external rotation during all three tasks. Correlations of the rearfoot supination/pronation with tibial rotations, knee, and hip motions in sagittal, frontal, and transverse planes were very strong to strong during double-leg landing and moderate to weak during gait. A weak correlation was observed between rearfoot supination/pronation and hip adduction/abduction during single-leg landing.

CONCLUSIONS

Coupling relationships between rearfoot, knee, and hip vary by the task intensity and alignment profiles in female juniors with DKV.

Effects of an Injury Prevention Program on Anterior Cruciate Ligament Injury Risk Factors in Adolescent Females at Different Stages of Maturation

The ideal timing to implement anterior cruciate ligament injury prevention programs with respect to maturation is unclear. The purpose of this study was to investigate the effects of an injury prevention program on knee mechanics in early-, late-, and post-pubertal females. In the study, 178 adolescent female basketball players were assigned to six groups: early-pubertal training, early-pubertal control, late-pubertal training, and late-pubertal control, post-pubertal training, and post-pubertal control. The training groups performed an injury prevention program for six months. Medial knee displacement, knee flexion range of motion, and the probability of high knee abduction moment were assessed before and after the training period. After the six-month training period, medial knee displacement was significantly increased in the early-pubertal control group whereas it was unchanged in the early-pubertal training group. Knee flexion range of motion was significantly decreased in the early-pubertal control group whereas it did not change in the early-pubertal training group. The probability of high knee abduction moment was increased in the early-pubertal control group whereas it was unchanged in the earl-pubertal training group. The probability of high knee abduction moment was also decreased in the post-pubertal training group whereas it did not change in the post-pubertal control group. The program limited the development of high-risk movement patterns associated with maturation in early puberty while improving the knee mechanics in post-pubertal adolescents. Therefore, an injury prevention program should be initiated in early puberty and continue through the post-puberty years.

Dynamic Knee Alignment and Pelvic Balance: Comparison Regarding Gender in Young Soccer Athletes

Objective  To evaluate knee alignment in the frontal plane and pelvic balance during the step-down test in female and male soccer players.

Methods  Cross-sectional study carried out with male and female soccer players from under-15 and under-17 teams of a professional club in Southern Brazil. The step-down test was performed, filmed with a video camera, and evaluated according to the angular measurements obtained during movement using the Kinovea software (open source), version 0.8.24.

Results  The sample consisted of 38 individuals, 19 males and 19 females. Female athletes had a greater varus angle (9.42° ± 1.65°) compared to male athletes (3.91° ± 2.0°; p  = 0.04). There was no difference regarding the unilateral pelvic drop between the groups. In addition, the association between the hip-related pelvic drop and the projection angle on the frontal plane of the knee was weak in both genders.

Conclusion  Even though the pelvic drop was observed in both genders, young female athletes had greater varus knee angles on the step-down test, which require greater attention to minimize the risk of injury.

Sex and Age Comparisons in Neuromuscular And Biomechanical Characteristics of the Knee in Young Athletes

BACKGROUND

The identification of risk factors for injury is a key step for musculoskeletal injury prevention in youth sports. Not identifying and correcting for injury risk factors may result in lost opportunity for athletic development. Physical maturation and sex affect these characteristics, which may indicate the need for both age and sex-based injury prevention programs.

HYPOTHESIS/PURPOSE

This study examined age and sex differences in knee strength, static balance, jump height, and lower extremity landing biomechanics in school- and high school-age athletes.

STUDY DESIGN

Cross-sectional.

METHODS

Forty healthy school aged (10.8±0.8 yrs) and forty high school (16.8±0.8 yrs) athletes completed isokinetic knee flexion and extension strength tests, single-leg static balance and single-leg vertical stop jump tasks.

RESULTS

High school athletes were significantly stronger (~67% and 35% stronger for males and females, respectively) and jumped higher (regardless of sex) compared to school age athletes. High school males had worse balance (~28%) compared to their younger counterparts. High school females had lower strength (~23%) compared to males but had better balance (~46%). Conclusion: Maturation had different effects on the variables analyzed and sex differences were mainly observed after maturation. These differences may be minimized through appropriate age and sex specific training programs.

LEVELS OF EVIDENCE

3a.

CLINICAL RELEVANCE

Neuromuscular and biomechanical differences between sex and age groups should be accounted for in injury prevention and rehabilitation. Inadequate training may be a primary factor contributing to injuries in a young athletic population. When designing training programs for long term athlete development, programs should be dependent on decrements seen at specific time points throughout maturation.What is known about the subject: Generally, both males and females get stronger and jump higher as they get older but the results comparing balance and biomechanics between genders or across age groups have been mixed.What this study adds to existing knowledge: The current study looks at multiple neuromuscular and biomechanical variables in male and female participants at different maturation statuses. The current data supports the significant changes observed in strength and jump height, as both genders age, but the data also demonstrates significant differences in balance between age groups in males and between genders in balance and knee flexion angles.

Can lower extremity anatomical measures and core stability predict dynamic knee valgus in young men?

INTRODUCTION

Dynamic knee valgus (DKV) is a risk factor for lower extremity injuries such as anterior cruciate ligament and patellofemoral pain syndrome. Purpose of the current study was to investigate the relationship between lower extremity anatomical measures (LEAM) and core stability with DKV during the single-leg squat.

METHODS

Thirty healthy men aged between 18 and 28 years participated in this cross-sectional biomechanical study.DKV was assessed using a 6-camera motion analysis system during a single-leg squat task. Anteversion of hip, hip internal and external rotation, Q-angle, knee hyperextension, tibial torsion, tibia vara, plantar arch index, and core stability were measured using standard clinical procedures. To predict DKV, a multiple linear regression model was used.

RESULT

The stability index negatively and plantar arch index positively predicted greater DKV during the single-leg squat task (P = 0.001 and P = 0.09, respectively). Research variables together predicted 82% of the variance in DKV (F(4,26) = 28.09, p < 0.001). However, relationships between other variables and DKV were not found.

CONCLUSION

The core stability index and plantar arch index were associated with observed DKV during the single-leg squat. These results suggested that proximal and distal variables to the knee should be considered when evaluating individuals who present DKV during the single-leg squat.

Generalized joint hypermobility, scoliosis, patellofemoral pain, and physical abilities in young dancers

Background

Many young girls with generalized joint hypermobility (GJH) choose to participate in dance because their bodies are suited for this activity. Scoliosis tends to occur often in thin girls, who also are more likely to choose dance. Both anomalies (GJH and scoliosis) may be related to reduced abilities such as diminished strength and insufficient postural balance, with increased risk for musculoskeletal conditions. The main objectives of the present study were to determine the prevalence of dancers with GJH, the prevalence of dancers with scoliosis, and the prevalence of dancers with these two anomalies; and, to determine differences in physical abilities and the presence of patellofemoral pain (PFP) between young female dancers with and without such anomalies.

Methods

One hundred thirty-two female dancers, aged 12–14 years, were assessed for anthropometric parameters, GJH, scoliosis, knee muscle strength, postural balance, proprioception ability, and PFP.

Results

GJH was identified in 54 dancers (40.9%) and scoliosis in 38 dancers (28.8%). Significant differences were found in the proportion of dancers with no anomalies (74 dancers, 56.1%) and dancers with both anomalies (34 dancers, 25.8%) (p < .001). Dancers with both anomalies had reduced dynamic postural balance in the anterior direction (p = .023), reduced proprioception ability (p < .001), and weaker knee extensors (p = .036) and flexors (p = .040) compared with dancers with no anomalies. Among dancers with both anomalies, 73.5% suffered bilateral PFP, 17.6% suffered unilateral PFP, and 8.8% had no PFP (p < .001).

Conclusions

A high prevalence of young girls participating in dance classes had GJH, as the increased joint flexibility probably provides them with some esthetic advantages. The high prevalence of scoliosis found in these young dancers might be attributed to their relatively low body mass, their delayed maturation, and the selection process of dancers. Dancers with both GJH and scoliosis had decreased muscle strength, reduced postural balance, reduced proprioception, with higher risk of PFP. The main clinical implications are the need to reduce the risk of PFP among dancers by developing appropriate strength and stabilizing exercises combined with proprioceptive and postural balance training, to improve the correct alignment of the hyperextended and hypermobile joints, and to improve their supporting muscle strength.

Factors associated with dynamic knee valgus angle during single-leg forward landing in patients after anterior cruciate ligament reconstruction

Background

A few studies have reported on how to predict increased dynamic knee valgus angle (KVA), a risk factor for second anterior cruciate ligament (ACL) injury after ACL reconstruction. This study aimed to identify the factors with the potential to predict the KVA during single-leg hop landing.

Methods

Using three-dimensional motion analysis systems, knee motion during a single-leg hop landing task was measured in 22 patients who had undergone ACL reconstruction at 8–10 months postoperatively. The KVA at initial contact (IC) and maximum KVA during the 40-ms period after IC were calculated using the point cluster technique; correlations between the KVA and other factors were assessed. We performed multiple regression analysis to determine whether KVA could be predicted by these parameters.

Results

The KVA was significantly negatively correlated with the static femorotibial angle (FTA; P < 0.01) and patient height (P < 0.01). It was positively correlated with the body mass index (P < 0.05). Multiple regression analysis showed that a small FTA could predict the KVA at IC (β: 0.52, 95% confidence interval (CI): 2.24-(-0.42); P < 0.01). The maximum KVA during the 40-ms period after IC was associated with the FTA (β: 0.46, 95% CI: 2.22-(-0.26); P = 0.02) and height (β: 0.40, 95% CI: 0.59-(-0.02); P = 0.04).

Conclusion

At 8–10 months after ACL reconstruction, the KVA was significantly correlated with the FTA, with reduced FTA being associated with an increased dynamic KVA during single-leg hop landing. The measurement of anatomical parameters may aid in predicting the second ACL injury risk after reconstruction.

The effect of silicone ankle sleeves and lace-up ankle braces on neuromuscular control, joint torque, and cutting agility

Objective

To evaluate the effects of silicone ankle sleeves (SASs) and lace-up ankle braces (LABs) on neuromuscular control, net joint torques, and cutting agility in healthy, active individuals.

Design

Markerless motion-capture technology tracked subjects fitted with SASs, LABs, or no brace while they performed the movements: Y-excursion, left cutting, right cutting, single-leg drop vertical jump (SLDVJ), 45-degree bound, and single-leg squat (SLS).

Setting

University Laboratory.

Participants

Ten healthy, active individuals (5 males and 5 females, mean ± SD 23.60 ± 1.43 years of age).

Main outcome measures

Degrees of joint range of motion (ROM), Newton-meters of joint torque, time to perform a cutting maneuver.

Results

SASs and LABs resulted in significantly different knee and ankle ROM and hip internal rotation in the SLDVJ, SLS, Y-excursion, cutting maneuver, and 45-degree bound when compared to control (p < .05). Both ankle and knee torque were significantly reduced in the 45-degree bound and cutting movements with both types of PABs (p < .05). There were minimal differences between the SASs and LABs for all conditions. There were no statistically significant differences in cutting times for any of the 3 conditions.

Conclusion

Both SAS and LAB positively impacted neuromuscular control, reduced net joint torque, and neither impaired cutting agility when compared to control.

Eccentric Resistance Training in Youth: Perspectives for Long-Term Athletic Development

The purpose of this narrative review is to discuss the role of eccentric resistance training in youth and how this training modality can be utilized within long-term physical development. Current literature on responses to eccentric exercise in youth has demonstrated that potential concerns, such as fatigue and muscle damage, compared to adults are not supported. Considering the importance of resistance training for youth athletes and the benefits of eccentric training in enhancing strength, power, speed, and resistance to injury, its inclusion throughout youth may be warranted. In this review we provide a brief overview of the physiological responses to exercise in youth with specific reference to the different responses to eccentric resistance training between children, adolescents, and adults. Thereafter, we discuss the importance of ensuring that force absorption qualities are trained throughout youth and how these may be influenced by growth and maturation. In particular, we propose practical methods on how eccentric resistance training methods can be implemented in youth via the inclusion of efficient landing mechanics, eccentric hamstrings strengthening and flywheel inertia training. This article proposes that the use of eccentric resistance training in youth should be considered a necessity to help develop both physical qualities that underpin sporting performance, as well as reducing injury risk. However, as with any other training modality implemented within youth, careful consideration should be given in accordance with an individual's maturity status, training history and technical competency as well as being underpinned by current long-term physical development guidelines.

Sex and Maturation Differences in Performance of Functional Jumping and Landing Deficits in Youth Athletes

CONTEXT

Understanding how neuromuscular and biomechanical deficits that are associated with knee injuries change as youth mature may improve injury prevention strategies in this population.

OBJECTIVE

To investigate sex and maturation differences in jump-landing technique performance in youths using a practical clinical tool.

DESIGN

Cross-sectional study.

SETTING

High Performance Center Laboratory.

PARTICIPANTS

A total of 165 youth athletes were included in this study.

MAIN OUTCOME MEASURES

The main outcome measures were each of the 10 items of the modified tuck jump assessment and the total score. These measures include (1) knee valgus at landing, (2) thighs do not reach parallel, (3) thighs not equal side to side, (4) foot placement not shoulder width apart, (5) foot placement not parallel, (6) foot contact timing not equal, (7) excessive landing contact noise, (8) pause between jumps, (9) technique declines prior to 10 seconds, and (10) does not land in same footprint.

RESULTS

Only knee valgus at landing had a significant sex × maturation interaction. The main effect of maturation was significant for items 2, 3, 6, 7, 9, and total score. Plyometric technique performance improved with increasing maturation. The main effect of sex was significant for items 1 and 9, with males performing better than females.

CONCLUSIONS

Female athletes demonstrate increased knee valgus at landing and fatigue relative to males during jump-landing performance. Overall, there was a trend of improved jump-landing performance with maturation.

Do neoprene sleeves and prophylactic knee braces affect neuromuscular control and cutting agility?

OBJECTIVES

To evaluate the effects of neoprene sleeves (NSs) and prophylactic knee braces (PKBs) on neuromuscular control and cutting agility.

DESIGN

Markerless motion-capture technology tracked subjects (1) without a brace as a control (2) with NSs and (3) with PKBs during single-leg drop vertical jump (SLDVJ), single-leg squat (SLS), Y-excursion, and cutting movements. Movements were recorded five times per bracing condition in three different sessions.

SETTING

University laboratory.

PARTICIPANTS

Ten healthy, active subjects (5 male, 5 female; age range, 22-26 years).

MAIN OUTCOME MEASURES

Degrees of motion and time to completion.

RESULTS

Use of NSs and PKBs reduced subjects' hip internal rotation in the loading phase of SLDVJ (p = 0.026, 0.02) and SLS (p = 0.005, <0.001), reduced knee flexion in the loading phase of SLDVJ (p = 0.038, <0.001), and reduced knee frontal plane abduction (FPA) with SLS (p = 0.015, 0.024) and Y-excursion (p = 0.002, 0.005) compared to control. Use of PKBs decreased subjects' hip internal rotation in the Y-excursion (p = 0.024) and reduced knee FPA in the SLDVJ loading phase (p = 0.014) compared to control. There was no difference in cutting agility for either group (p = 0.145, 0.347).

CONCLUSION

Both NSs and PKBs positively impacted neuromuscular control without impacting cutting agility.

Risk factor heterogeneity for medial and lateral compartment knee osteoarthritis: analysis of two prospective cohorts

OBJECTIVE

To evaluate the etiologic heterogeneity between medial and lateral tibiofemoral radiographic osteoarthritis (ROA).

METHODS

Knees without medial or lateral tibiofemoral ROA at baseline were followed for 60-month in Multicenter Osteoarthritis Study (MOST) and for 48-month in Osteoarthritis Initiative (OAI). We examined the relation of previously reported risk factors to incident medial and lateral tibiofemoral ROA separately and determined the etiology heterogeneity with a ratio of rate ratios (RRs) (i.e., the RR for medial tibiofemoral ROA divided by the RR for lateral tibiofemoral ROA) using a duplication method for Cox proportional hazard regression.

RESULTS

Of 2,016 participants in MOST, 436 and 162 knees developed medial or lateral tibiofemoral ROA, respectively. Obesity and varus malalignment were 95% and 466% more strongly associated with incident medial tibiofemoral ROA than with lateral tibiofemoral ROA, respectively (ratios of RRs, 1.95 [95% confidence interval (CI):1.05-3.62] and 5.66 [95% CI:3.20-10.0]). In contrast, the associations of female sex and valgus malalignment with incident medial tibiofemoral ROA were weaker or in an opposite direction compared with lateral tibiofemoral Osteoarthritis (OA) (ratios of RRs, 0.40 [95% CI:0.26-0.63] and 0.20 [95% CI:0.12-0.34], respectively). Older age tended to show a weaker association with incident medial tibiofemoral ROA than with incident lateral tibiofemoral ROA. No heterogeneity was observed for the relation of race, knee injury, or contralateral knee ROA. These findings were closely replicated in OAI.

CONCLUSION

Risk factor profiles for medial and lateral tibiofemoral ROA are different. These results can provide a framework for the development of targeted prevention and potential treatment strategies for specific knee OA subtypes.

A Review of Field-Based Assessments of Neuromuscular Control and Their Utility in Male Youth Soccer Players

Read, PJ, Oliver, JL, Croix, MS, Myer, GD, and Lloyd, RS. A review of field-based assessments of neuromuscular control and their utility in male youth soccer players. J Strength Cond Res 33(1): 283-299, 2019-Lower-extremity injuries in male youth soccer are common and equate to a substantial time loss from training and competitions during the course of a season. Extended periods of absence will impact player involvement in skill and physical development activities, as well as participation in competitive match play. Neuromuscular risk factors for lower-extremity injury in male youth soccer players can be categorized into quadriceps dominance, leg dominance, ligament dominance, trunk dominance, and reduced dynamic stability. Valid screening methods to identify risk factors that are practically viable are needed for youth athletes who may be at a greater risk of injury in soccer. Although field-based tests of neuromuscular control provide a reliable option for the assessment of injury risk in adults and females, less data are available in male youth soccer players, and further research is required to examine their ability to predict injury risk. This article provides a review of the current literature pertaining to field-based screening tests and critically appraises their suitability for use with male youth soccer players. Currently, the only method that has been validated in male youth soccer players is the landing error scoring system. Asymmetrical anterior reach measured during the Y-Balance test may also be considered because of its strong predictive ability in male youth basketball players; however, further research is required to fully support its use with soccer players.

Sex differences in sagittal plane control emerge during adolescent growth: a prospective investigation

PURPOSE

Females athletes have a higher incidence of non-contact knee joint injuries compared to their male counterparts. This may be attributable to sex-specific differences in neuromuscular control, which arise during the pubertal growth spurt. The purpose of this longitudinal study was to assess the development of landing kinematics of adolescent male and female athletes during the adolescent growth-spurt.

METHODS

One hundred and eighty-four adolescent athletes (55% male, 45% female; mean age = 13 ± 0.3 years) participated. Testing was undertaken at baseline and then repeated at 6, 12, 18 and 24 months. Participants performed three drop vertical jump (DVJ) trials from a 31 cm box. Frontal and sagittal plane knee joint angles were recorded. The average measurement of the three jumps was used for analysis at each time point. To assess maturation status, participants were categorised according to their age from peak height velocity at baseline. Pre-initial contact knee flexion (pre-IC), peak knee flexion and knee valgus displacement were the dependant variables. The categorical independent variables were sex (male versus female) and time.

RESULTS

There was a significant sex*time interaction for pre-IC knee flexion, with males increasing knee flexion with time to a greater extent than females. There was no significant sex*time interaction for knee valgus displacement; although females displayed greater knee valgus displacement across all time points.

CONCLUSIONS

Adolescent male and female athletes display differing kinematic profiles across growth and development. This has clinical relevance for emphasising increased knee flexion, as well as decreasing abnormal frontal plane displacement in injury prevention programmes for adolescent females.

LEVEL OF EVIDENCE

II.

Systematic Selection of Key Logistic Regression Variables for Risk Prediction Analyses: A Five-Factor Maximum Model

GENERAL AND CRITICAL REVIEW FORMAT

The evolution of clinical practice and medical technology has yielded an increasing number of clinical measures and tests to assess a patient's progression and return to sport readiness after injury. The plethora of available tests may be burdensome to clinicians in the absence of evidence that demonstrates the utility of a given measurement.

OBJECTIVE

Thus, there is a critical need to identify a discrete number of metrics to capture during clinical assessment to effectively and concisely guide patient care.

DATA SOURCES

The data sources included Pubmed and PMC Pubmed Central articles on the topic. Therefore, we present a systematic approach to injury risk analyses and how this concept may be used in algorithms for risk analyses for primary anterior cruciate ligament (ACL) injury in healthy athletes and patients after ACL reconstruction.

MAIN RESULTS

In this article, we present the five-factor maximum model, which states that in any predictive model, a maximum of 5 variables will contribute in a meaningful manner to any risk factor analysis.

CONCLUSIONS

We demonstrate how this model already exists for prevention of primary ACL injury, how this model may guide development of the second ACL injury risk analysis, and how the five-factor maximum model may be applied across the injury spectrum for development of the injury risk analysis.

Coordination and variability during anticipated and unanticipated sidestepping

BACKGROUND

Numerous investigations have attempted to link the incidence and risk of non-contact anterior cruciate ligament injuries to specific intrinsic and extrinsic mechanisms. However, these are often measured in isolation.

RESEARCH QUESTION

This study utilizes a dynamical systems approach to investigate differences in coordination and coordination variability between segments and joints in anticipated and unanticipated sidestepping, a task linked to a high risk of non-contact anterior cruciate ligament injuries.

METHODS

Full body, three-dimensional kinematics and knee kinetic data were collected on 22 male collegiate soccer players during anticipated and unanticipated sidestepping tasks. A modified vector coding technique was used to quantify coordination and coordination variability of the trunk and pelvis segments and the hip and knee joints.

RESULTS

Sagittal and frontal plane trunk-pelvis coordination were more in-phase during unanticipated sidestepping. Sagittal plane hip-knee and hip (rotation)-knee (flexion/extension) coordination were more in-phase with the knee dominating the movement during unanticipated sidestepping (P < 0.05). Coordination variability was greater in unanticipated sidestepping for trunk (flexion)-pelvis (tilt), trunk (lateral flexion)-pelvis (obliquity), hip (flexion/extension)-knee (flexion/extension) and hip (rotation)-knee (flexion/extension) (P < 0.05). In unanticipated sidestepping where there is limited time to pre-plan the movement, multiple kinematic solutions and high coordinative variability is required to achieve the task.

SIGNIFICANCE

Our results suggest that coordination becomes more in-phase and the variability of this coordination increases as a function of task complexity and reduced planning time as that which occurs in unanticipated sporting task scenarios. Consequently, injury prevention programs must incorporate perceptual components in order to optimise planning time and coordinate appropriate postural adjustments to reduce external knee joint loading and subsequent injury risk in sport.

Quantitative and qualitative assessment of frontal plane knee motion in males and females: A reliability and validity study

BACKGROUND

The aim was to determine reliability and validity of frontal plane projection angle (FPPA) and visual assessments (VA) in both males and females.

METHODS

Fifty-four participants (30 females) performed lateral step-downs while kinematics were recorded by two-dimensional and three-dimensional analyses. Two raters viewed the videos, extracted images, and measured the FPPA (quantitative). Using the videos, the raters also categorized (qualitative VA) each participant's motion as demonstrating dynamic valgus (>10° valgus), dynamic varus (>10° varus), or no change. Reliability was assessed for FPPA and VA using intraclass correlation coefficients and Kappa, respectively. Validity was determined by comparing the FPPA to three-dimensional measures (Pearson correlations) and comparing the VA to both FPPA and standard reference 3D kinematics (Kappa).

RESULTS

FPPA showed good-excellent reliability (ICC = 0.850-0.998). VA showed minimal-moderate reliability (κ = 0.370-0.766). The FPPA showed large correlations (r = -0.514-0.531) with hip adduction in both sexes but only a moderate relationship with knee abduction in males (r = 0.427-0.445). VA showed no-weak (κ = 0.153-0.475) and weak-moderate (κ = 0.455-0.698) agreement compared to FPPA and no-weak (κ = -0.300-0.183) and no-minimal (κ = -0.078-0.027) disagreement compared to the reference standard 3D kinematics in males and females, respectively.

CONCLUSION

The quantitative FPPA is more reliable and valid than qualitative VA of frontal knee plane motion.

Altered landing mechanics are shown by male youth soccer players at different stages of maturation

OBJECTIVES

Examine the effects of maturation on single leg jumping performance in elite male youth soccer players.

DESIGN

Cross sectional.

SETTING

Academy soccer clubs.

PARTICIPANTS

347 male youth players classified as either pre, circa or post-peak height velocity (PHV).

MAIN OUTCOME MEASURES

Single leg countermovement jump (SLCMJ) height, peak vertical landing forces (pVGRF), knee valgus and trunk side flexion.

RESULTS

Vertical jump height and absolute pVGRF increased with each stage of maturation (p < 0.001; d = 0.85-2.35). Relative to body weight, significantly higher landing forces were recorded on the left leg in circa versus post-PHV players (p < 0.05; d = -0.40). Knee valgus reduced with maturation but the only notable between-group differences were shown in post-PHV players (p < 0.05; d = 0.67); however, greater ipsilateral lateral trunk flexion angles was also present and these differences were significantly increased relative to circa-PHV players (p < 0.05; d = 0.85).

CONCLUSION

Periods of rapid growth are associated with landing kinetics which may heighten injury risk. While reductions in knee valgus were displayed with maturation; a compensatory strategy of greater trunk lateral flexion was evident in post-PHV players and this may increase the risk of injury.

Landing Kinematics in Elite Male Youth Soccer Players of Different Chronologic Ages and Stages of Maturation

CONTEXT

  Despite the high frequency of knee injuries in athletes, few researchers have studied the effects of chronologic age and stage of maturation on knee-joint kinematics in male youth soccer players.

OBJECTIVE

  To use a coach-friendly screening tool to examine knee-valgus scores for players of different ages and at different stages of maturation.

DESIGN

  Cross-sectional study.

SETTING

  Academy soccer clubs.

PATIENTS OR OTHER PARTICIPANTS

  A total of 400 elite male youth soccer players aged 10 to 18 years categorized by chronologic age and stage of maturation based on their years from peak height velocity (PHV).

MAIN OUTCOME MEASURE(S)

  Knee valgus was evaluated during the tuck-jump assessment via 2-dimensional analysis. Frontal-plane projection angles were subjectively classified as minor (<10°), moderate (10°-20°), or severe (>20°), and using these classifications, we scored knee valgus in the tuck jump as 0 ( no valgus), 1 ( minor), 2 ( moderate), or 3 ( severe).

RESULTS

  A trend toward higher valgus scores was observed in the younger age groups and the pre-PHV group. The lowest frequency of no valgus occurred in the U18 and post-PHV groups. The highest percentages of severe scores were in the U13 and pre-PHV groups for the right limb. Knee-valgus scores were lower for both lower extremities in the U18 group than in all other age groups ( P < .001) except the U16 group. Scores were lower for the post-PHV than the pre-PHV group for the right limb ( P < .001) and both pre-PHV and circa-PHV groups for the left limb ( P < .001). Noteworthy interlimb asymmetries were evident in the U14, U15, and circa-PHV groups.

CONCLUSIONS

  Reductions in knee valgus with incremental age and during the later stages of maturation indicated that this risk factor was more prevalent in younger players. Interlimb asymmetry may also emerge around the time of the peak growth spurt and early adolescence, potentially increasing the risk of traumatic injury.

Biomechanical Differences of Multidirectional Jump Landings Among Female Basketball and Soccer Players

Taylor, JB, Ford, KR, Schmitz, RJ, Ross, SE, Ackerman, TA, and Shultz, SJ. Biomechanical differences of multidirectional jump landings among female basketball and soccer players. J Strength Cond Res 31(11): 3034-3045, 2017-Anterior cruciate ligament (ACL) injury prevention programs are less successful in basketball than soccer and may be due to distinct movement strategies that these athletes develop from sport-specific training. The purpose of this study was to identify biomechanical differences between female basketball and soccer players during multidirectional jump landings. Lower extremity biomechanics of 89 female athletes who played competitive basketball (n = 40) or soccer (n = 49) at the middle- or high-school level were analyzed with 3-dimensional motion analysis during a drop vertical jump, double- (SAG-DL) and single-leg forward jump (SAG-SL), and double- (FRONT-DL) and single-leg (FRONT-SL) lateral jump. Basketball players landed with either less hip or knee, or both hip and knee excursion during all tasks (p ≤ 0.05) except for the SAGSL task, basketball players landed with greater peak hip flexion angles (p = 0.04). The FRONT-SL task elicited the most distinct sport-specific differences, including decreased hip adduction (p < 0.001) angles, increased hip internal rotation (p = 0.003), and increased relative knee external rotation (p = 0.001) excursions in basketball players. In addition, the FRONT-SL task elicited greater forces in knee abduction (p = 0.003) and lesser forces in hip adduction (p = 0.001) and knee external rotation (p < 0.001) in basketball players. Joint energetics were different during the FRONT-DL task, as basketball players exhibited less sagittal plane energy absorption at the hip (p < 0.001) and greater hip (p < 0.001) and knee (p = 0.001) joint stiffness. Sport-specific movement strategies were identified during all jump landing tasks, such that soccer players exhibited a more protective landing strategy than basketball players, justifying future efforts toward sport-specific ACL injury prevention programs.

Ultrasonography and clinical examination of knee injuries in pre- and post- menarche dancers

This study aimed at evaluating whether the prevalence of knee injuries and morphological features are different among pre-and-post menarche dancers; Sixty-seven pre-and-post menarche dancers were screened for anthropometric parameters; knee laxity; patella femoral pain syndrome (PFPS), pathologies and anatomical structure of the knees. Both groups showed a high and similar prevalence of PFPS. The post-menarche dancers produced a significantly higher rate of Tanner stages 3-4 (p = .010), greater weight (p < .001) higher BMI (p = .003); and, higher prevalence of MCL pathology, pes planus, and scoliosis compared with pre-menarche dancers (p < .05). The pre-menarche dancers started dance practice earlier (p = .008); and, showed significantly higher prevalence of lateral laxity, patellar laxity, positive Lachman test and positive Drawer test compared with post-menarche dancers (p < .05). Interactions (menarche yes/no by PFPS no/one leg/both legs) were found for BMI (p = .044; η² = .187), trochlear cartilage thickness (p = .020; η² = 0.121) and tip of patella - trochlear groove distance (p = .024; η² = .150). Pre-and-post-menarche female dancers demonstrated similar prevalence of knee injuries, with different body morphology.

Ultrasonography findings and physical examination outcomes in dancers with and without patellofemoral pain

OBJECTIVES

To identify whether a physical examination for patello-femoral pain (PFP) is related to ultrasonography findings at the knee, and to identify possible factors related to PFP in young dancers.

METHODS

Sixty-seven young female dancers (7th grade, aged 12.8 ± 0.5) from three schools with identical special dance programs were included in the study. All the dancers were interviewed for demographic details, dance background, and training intensity; were evaluated for anthropometric measurements; underwent physical examination of both knees for PFP and for knee range of motion (ROM); and, had ultrasonography assessment for pathologies and of anatomical parts of their knees.

RESULTS

PFP was found in 54.5% of the 134 knees physically examined. In ultrasonography assessment, infra-articular effusion was found in 46.2% of the knees examined. H/week of dance practice was significantly higher among dancers with PFP (in both knees) compared with dancers with no PFP (p < .05). Knees with PFP had a significantly higher prevalence of intra articular effusion (p = .018) and higher prevalence of genu-recurvatum (p = .042). Knees with PFP had significantly greater growth plate width-anterior tibial tuberosity (p = .022) and a greater bony trochlear groove angle (p = .048).

CONCLUSION

This study describes the relationship between physical examination for PFP and the sonographic findings, and the factors related to knee injuries. The results showed a high prevalence of PFP and intra articular knee effusion among young dancers at the age of 12-13 years; and, that the number of hours of practice and anatomical structure are related to PFP. Our results should alert physicians, physiotherapists, athletic trainers and dance teachers to the need for devising modifications of training and injury prevention strategies from a young age (<12 years old).

Adding a post-training FIFA 11+ exercise program to the pre-training FIFA 11+ injury prevention program reduces injury rates among male amateur soccer players: a cluster-randomised trial

QUESTION

Does adding a post-training Fédération Internationale de Football Association (FIFA) 11+ exercise program to the pre-training FIFA 11+ injury prevention program reduce injury rates among male amateur soccer players?

DESIGN

Cluster-randomised, controlled trial with concealed allocation.

PARTICIPANTS

Twenty-one teams of male amateur soccer players aged 14 to 35 years were randomly assigned to the experimental group (n=10 teams, 160 players) or the control group (n=11 teams, 184 players).

INTERVENTION

Both groups performed pre-training FIFA 11+ exercises for 20minutes. The experimental group also performed post-training FIFA 11+ exercises for 10minutes.

OUTCOME MEASURES

The primary outcomes measures were incidence of overall injury, incidence of initial and recurrent injury, and injury severity. The secondary outcome measure was compliance to the experimental intervention (pre and post FIFA 11+ program) and the control intervention (pre FIFA 11+ program).

RESULTS

During one season, 26 injuries (team mean=0.081 injuries/1000 exposure hours, SD=0.064) were reported in the experimental group, and 82 injuries were reported in the control group (team mean=0.324 injuries/1000hours, SD=0.084). Generalised Estimating Equations were applied with an intention-to-treat analysis. The pre and post FIFA 11+ program reduced the total number of injuries (χ² (1)=11.549, p=0.001) and the incidence of initial injury (χ² (2)=8.987, p=0.003) significantly more than the pre FIFA 11+ program alone. However, the odds of suffering a recurrent injury were not different between the two groups (χ² (1)=2.350, p=0.125). Moreover, the severity level of injuries was not dependent upon whether or not the pre and post FIFA 11+ program was implemented (χ² (1)=0.016, p=0.898).

CONCLUSION

Implementation of the FIFA 11+ program pre-training and post-training reduced overall injury rates in male amateur soccer players more than the pre FIFA 11+ program alone.

TRIAL REGISTRATION

ACTRN12615001206516. [Al Attar WSA, Soomro N, Pappas E, Sinclair PJ, Sanders RH (2017) Adding a post-training FIFA 11+ exercise program to the pre-training FIFA 11+ injury prevention program reduces injury rates among male amateur soccer players: a cluster-randomised trial. Journal of Physiotherapy 63: 235-242].

Does Kinesio taping correct exaggerated dynamic knee valgus? A randomized double blinded sham-controlled trial

BACKGROUND

Deficiency in hip girdle neuromuscular control can cause exaggerated Dynamic Knee Valgus (DKV) which afflicts the knee joint and lead to knee injuries especially ACL injury in sports. Though Kinesio taping (KT) is known to improve function, stability and proprioception, the evidence is inconclusive on its effectiveness in athletes. We hypothesized that kinesio taping could enhance neuromuscular control of the hip girdle there by causing a reduction in DKV.

AIM/OBJECTIVE

To determine whether KT on Gluteus medius can correct exaggerated dynamic knee valgus and improves hip abductor strength when compared to sham KT.

METHOD

40 collegiate level athletes, aged between 18 and 28 years, of both genders with presence of dynamic knee valgus (>8° for men and >13° for women) were recruited in the study. Athletes were excluded if they had history of lower back pain, history of any injury or surgery to the lower extremities during the past year. Subjects who met the inclusion criteria were randomized into kinesio taping (KT) group and sham taping (ST) group. The Drop Jump test and the Donnatelli Drop Leg Test (DDT) were performed before, and on the third day, immediately after the application of KT on them and documented.

RESULTS

There was a significant reduction in DKV among male [4.0° (95% CI 3.5-4.5); p < 0.001] and female [4.3° (95% CI 3.5-5.2); p < 0.002] immediately after application of taping but not on the third day after application of KT. There was a significant rise in DDT immediately and on the third day after application of KT between KT group and SC group.

CONCLUSION

There was a reduction in DKV immediately after the application of KT. However, there was no significant difference between KT group and SC group on the third day. Meanwhile, gluteus medius strength also showed significant improvement immediately after taping and it was maintained even on the third day.

Real-time optimized biofeedback utilizing sport techniques (ROBUST): a study protocol for a randomized controlled trial

Background

Anterior cruciate ligament (ACL) injuries in female athletes lead to a variety of short- and long-term physical, financial, and psychosocial ramifications. While dedicated injury prevention training programs have shown promise, ACL injury rates remain high as implementation has not become widespread. Conventional prevention programs use a combination of resistance, plyometric, balance and agility training to improve high-risk biomechanics and reduce the risk of injury. While many of these programs focus on reducing knee abduction load and posture during dynamic activity, targeting hip extensor strength and utilization may be more efficacious, as it is theorized to be an underlying mechanism of injury in adolescent female athletes. Biofeedback training may complement traditional preventive training, but has not been widely studied in connection with ACL injuries. We hypothesize that biofeedback may be needed to maximize the effectiveness of neuromuscular prophylactic interventions, and that hip-focused biofeedback will improve lower extremity biomechanics to a larger extent than knee-focused biofeedback during dynamic sport-specific tasks and long-term movement strategies.

Methods

This is an assessor-blind, randomized control trial of 150 adolescent competitive female (9–19 years) soccer players. Each participant receives 3x/week neuromuscular preventive training and 1x/week biofeedback, the mode depending on their randomization to one of 3 biofeedback groups (hip-focused, knee-focused, sham). The primary aim is to assess the impact of biofeedback training on knee abduction moments (the primary biomechanical predictor of future ACL injury) during double-leg landings, single-leg landings, and unplanned cutting. Testing will occur immediately before the training intervention, immediately after the training intervention, and 6 months after the training intervention to assess the long-term retention of modified biomechanics. Secondary aims will assess performance changes, including hip and core strength, power, and agility, and the extent to which maturation effects biofeedback efficacy.

Discussion

The results of the Real-time Optimized Biofeedback Utilizing Sport Techniques (ROBUST) trial will help complement current preventive training and may lead to clinician-friendly methods of biofeedback to incorporate into widespread training practices.

Trial registration

Date of publication in ClinicalTrials.gov: 20/04/2016. ClinicalTrials.gov Identifier: NCT02754700.

Lower extremity and spine characteristics in young dancers with and without patellofemoral pain

Very little is known about patellofemoral pain syndrome (PPFS) among young dancers. Understanding the mechanism of the injury and implementing a preventative programme are important in order to minimize the risk of PFPS. The aim of the current study is to determine the extent to which factors such as lower extremity and back characteristics are common among dancers with PFPS. The study population included 271 dancers with PFPS and 271 non-injured dancers, aged 10-16 years. All dancers were screened for morphometric profile, dance discipline (h/week), anatomical anomalies (present/absent of scoliosis, genu valgus/varum, etc.), and joint range of motion (measured by goniometer at the hip, knee, ankle, foot, and spinal joints). The predicting factors for PFPS among young dancers (10-11 years old) were: hyper hip abduction (OR = 0.906) and lower back and hamstring flexibility (OR = 3.542); for adolescent dancers (12-14 years old): hyper ankle dorsiflexion (OR = 0.888), hind foot-varum (OR = 0.260), and mobility of patella (OR = 2.666); and, for pre-mature dancers (15-16 years old): scoliosis (OR = 5.209), limited ankle plantar-flexion (OR = 1.060), and limited hip internal rotation (OR = 1.063). In conclusion, extrinsic and intrinsic parameters predisposing the dancers to knee injuries should be identified by screening in early stages of dance classes.

Biomechanical Comparison of Single- and Double-Leg Jump Landings in the Sagittal and Frontal Plane

BACKGROUND

Double-leg forward or drop-jump landing activities are typically used to screen for high-risk movement strategies and to determine the success of neuromuscular injury prevention programs. However, research suggests that these tasks that occur primarily in the sagittal plane may not adequately represent the lower extremity biomechanics that occur during unilateral foot contact or non-sagittal plane movements that are characteristic of many multidirectional sports.

PURPOSE

To examine the extent to which lower extremity biomechanics measured during a jump landing on a double leg (DL) after a sagittal plane (SAG) movement is representative of biomechanics measured during single-leg (SL) or frontal plane (FRONT) jump landing tasks.

STUDY DESIGN

Controlled laboratory study.

METHODS

Lower extremity biomechanics were measured in 15 recreationally active females (mean age [±SD], 19.4 ± 2.1 years; mean height, 163.3 ± 5.9 cm; mean weight, 61.1 ± 7.1 kg) while performing SAGDL, SAGSL, FRONTDL, and FRONTSL jump landing tasks. Repeated-measures analyses of variance examined differences in lower extremity biomechanics between the 4 tasks, and linear regressions examined the extent to which an individual's biomechanics during SAGDL were representative of their biomechanics during SAGSL, FRONTDL, and FRONTSL.

RESULTS

Lower extremity kinematics and kinetics differed by condition, with the SAGDL task generally eliciting greater hip and knee flexion angles and lower hip and knee forces than the other tasks (P < .05). Although biomechanics during the SAGDL task were strongly associated with those during the FRONTDL task (R (2), 0.41-0.82), weaker associations were observed between SAGDL and single-leg tasks for hip kinematics (R (2), 0.03-0.25) and kinetics (R (2), 0.05-0.20) and knee abduction moments (R (2), 0.06-0.18) (P < .05).

CONCLUSION

Standard double-leg sagittal plane jump landing tasks used to screen for ACL injury risk and the effectiveness of ACL injury prevention programs may not adequately represent the lower extremity biomechanics that occur during single-leg activities.

CLINICAL RELEVANCE

These results support further investigation of single-leg multidirectional landings to identify high-risk movement strategies in female athletes playing multidirectional sports.

Examination of the Effectiveness of Predictors for Musculoskeletal Injuries in Female Soldiers

The amount of training days lost to injury during military training has highlighted the need to identify a screening tool to predict injury. One hundred and fifty-eight female soldiers from the Combat Fitness Instructor Course (CFIC) of the Israel Defense Forces volunteered to participate in this study. All soldiers were free of orthopedic and neurologic conditions for at least one month before the study. All participants performed a battery of measurements during the first week of the course. Measures included anthropometric, functional movement screen (FMS), power performances (counter movement jump [CMJ], drop jump, single leg triple hop jump [SLTH], 10-m sprint) and a 2K run. Injury data was collected throughout the 3 month course. Median tests were used to compare between injured/non-injured soldiers. Chi-square and/or logistic regression analysis was used to examine the association between various predictors and injury. Percent body fat [%BF] was higher (p = 0.04), distance for SLTH was less for both left and right legs (p = 0.029, p = 0.047 respectively) and 2K run was slower (p =0.044) in injured compared to non-injured soldiers. No differences between groups were noted in total FMS score, however more zero scores in one or more movement pattern were found in the injured group (51.35 % vs. 30.5% p=0.0293). Only %BF, 2K run and SLTH distance were significant predictors of injury (p = 0.05, p = 0.02, p =0.016 respectively). The results of this study indicated that the FMS total score is not a predictor of injury in female soldiers in a CFIC. We found that %BF, SLTH, 2K run time, 10 meter sprint time and zero scores differentiated between injured and non-injured soldiers. In addition, %BF, 2K run and SLTH were each found to be separate predictors of injury. Further research is needed to determine threshold scores that predict injury. Key pointsA total of 145 injuries were reported during the three month Combat Fitness Instructor Course in a female soldiers, 37 of these injuries resulted in absence from at least two days of training.FMS total score is not a predictor of injury in female soldiers in a CFIC. However, a score of zero, which is indicative of pain during movement, could serve as a warning sign for potential injury.%BF, SLTH, 10 meter sprint, 2K run and number of zero scores in FMS appear to differentiate between injured and non-injured soldiersSLTH, 2K run and body fat % are each separate predictors of injury for female soldiers in the CFIC.

Sex differences in trunk, pelvis, hip and knee kinematics and eccentric hip torque in adolescents

BACKGROUND

Adolescents have a high incidence of knee joint dysfunctions, with up to 28% of adolescents reporting knee pain. Although adolescent females have a greater incidence of knee injuries in comparison to males, few studies conducted biomechanical evaluations in this population aiming to identify sex differences. If trunk and/or lower limb biomechanical impairments are identified in female adolescents, the implementation of early interventions for injury prevention will be better justified. The purpose of this study was to compare the trunk, pelvis, hip and knee kinematics during a single-leg squat task, as well as the isokinetic eccentric hip torque, between male and female healthy adolescents.

METHODS

Forty-four healthy adolescents were divided into two groups, group of males (n=22) and group of females (n=22). Kinematics during single-leg squat were assessed using a electromagnetic tracking system. For the evaluation of eccentric hip torque in the three planes an isokinetic dynamometer was used. Group differences were assessed using a one-way multivariate analysis of variance.

FINDINGS

Results showed that adolescent females presented greater hip adduction, hip external rotation and knee abduction, as well as smaller trunk flexion during single-leg squat in comparison to males. Additionally, adolescent females showed smaller isokinetic eccentric hip torque normalized by body mass in all planes in comparison to males.

INTERPRETATION

These sex differences in terms of trunk/lower limb kinematics and eccentric hip torque generation might play an important role in the greater incidence of overuse knee injuries observed in adolescent females.

Effect of injury prevention training on knee mechanics in female adolescents during puberty

PURPOSE/BACKGROUND

Female adolescents change their landing mechanics during puberty. It is unknown whether implementation of anterior cruciate ligament (ACL) injury prevention training reduces the loss of knee control in female athletes during puberty. The purpose of this study was to evaluate the effect of injury prevention training on dynamic knee alignment in female basketball players specifically when the knee mechanics were changing during puberty.

METHODS

Sixty female junior high school basketball players participated and were divided into two groups: a training group (n = 32) and a control group (n = 28). The training group underwent an injury prevention program for 6 months, whereas the control group maintained a regular training routine. The knee valgus motion and knee flexion range of motion during a drop vertical jump were measured before and after the training period. The probability of a high knee abduction moment (pKAM) was also evaluated using an ACL injury prediction algorithm.

RESULTS

The knee valgus motion was significantly increased in the control group (p < 0.001), whereas it did not change in the training group (p = 0.64). Similarly, the knee flexion range of motion was significantly decreased in the control group (p < 0.001), whereas it was not changed in the training group (p = 0.55). The pKAM was significantly increased in the control group (p < 0.001), but not in the training group (p = 0.06).

CONCLUSIONS

Implementation of injury prevention training was effective in limiting the loss of knee control in female athletes during puberty. Lowering the risk of ACL injury might be possible in this population.

LEVEL OF EVIDENCE

2b.

Influence of lean body mass and strength on landing energetics

PURPOSE

Less lean body mass may limit one's ability to produce adequate muscle forces to safely control landing from a jump, thus increasing the risk for injury. The primary objective of this study was to determine the effect of lower extremity lean mass (LELM) and eccentric muscle strength on lower extremity energy absorption (EA) during a drop jump landing.

METHODS

Seventy athletic subjects (35 men and 35 women) were measured for LELM with dual-energy x-ray absorptiometry, maximal eccentric strength of the quadriceps (QuadECC) and hamstrings (HamECC), and lower extremity joint energetics during the initial landing of a drop jump. A mediation analysis examined the extent to which LELM predicted EA at each lower extremity joint (EAHIP, EAKNEE, and EAANK) and subsequently whether these relationships were mediated by each subject's maximal eccentric strength capabilities.

RESULTS

LELM was a significant predictor of EAKNEE (R = 0.22, P < 0.01) in females but not in males (R = 0.03, P = 0.16). In females, QuadECC was a significant mediator of the effect of LELM on EA at the knee (ab = 179.72, 95% confidence interval [CI] = 10.43-423.42) and ankle (ab = 1.71, 95% CI = [0.16, 3.94]), whereas HamECC was a significant mediator of the relationship between LELM and EAHIP (ab = 4.89, 95% CI = 2.05-8.40). No significant relationships were observed in males.

CONCLUSIONS

LELM was a significant factor in energetic capabilities for females but not males. For females, this relationship was evident secondary to the stronger underlying relationship between maximal strength and EA. Thus, the maximal eccentric strength capabilities may be a more important determinant of energetic behaviors compared with the available quantity of lean mass alone. More work is needed to investigate these relationships and to reveal the underlying sex-specific mechanisms that determine EA capabilities.

Identifying multiplanar knee laxity profiles and associated physical characteristics

CONTEXT

A single measure of knee laxity (ie, measurement of laxity in a single plane of motion) is probably inadequate to fully describe how knee joint laxity is associated with anterior cruciate ligament injury.

OBJECTIVE

To characterize interparticipant differences in the absolute and relative magnitudes of multiplanar knee laxity (ie, sagittal, frontal, and transverse planes) and examine physical characteristics that may contribute to these differences.

DESIGN

Descriptive laboratory study.

SETTING

University research laboratory.

PATIENTS OR OTHER PARTICIPANTS

140 participants (90 women, 50 men).

MAIN OUTCOME MEASURE(S)

Using cluster analysis, we grouped participants into distinct multiplanar knee laxity profiles based on the absolute and relative magnitudes of their anterior knee laxity (AKL), genu recurvatum (GR), and varusvalgus (VV) and internal-external rotation (IER) knee laxity. Using multinomial logistic regression, we then examined associations between the different laxity profile clusters and physical characteristics of sex, age, activity level, general joint laxity, body mass index, thigh strength, and 8 measures of lower extremity anatomical alignment.

RESULTS

Six clusters were identified: low (LOW), moderate (MOD) and high (HIGH) laxity overall and disproportionally higher VV/IER (MOD(VV/IER)), GR (HIGH(GR)), and AKL (HIGH(AKL)) laxity. Once all other physical characteristics were accounted for, the LOW cluster was more likely to be older, with longer femur length. Clusters with greater magnitudes of VV and IER laxity were more likely to be younger and to have lower body mass index, smaller Q-angle, and shorter femur length (MOD, HIGH, MOD(VV/IER)) and less thigh strength (HIGH). The HIGH(GR) cluster was more likely to be female and to have a smaller tibiofemoral angle and longer femur length. The HIGH(AKL) cluster was more likely to have greater hip anteversion and navicular drop.

CONCLUSIONS

The absolute and relative magnitudes of a person's multiplanar knee laxity are not always uniform across planes of motion and can be influenced by age, body composition, thigh strength, and structural alignment. Except in HIGH(GR), sex was not a significant predictor of cluster membership once other physical characteristics were taken into account.

The effects of a valgus collapse knee position on in vivo ACL elongation

There are conflicting data regarding what motions increase ACL injury risk. More specifically, the mechanical role of valgus collapse positions during ACL injury remains controversial. Our objective was to evaluate ACL elongation in a model that mimics knee movements thought to occur during ACL injury. Eight healthy male subjects were imaged using MR and biplanar fluoroscopy to measure the in vivo elongation of the ACL and its functional bundles during three static knee positions: full extension, 30° of flexion, and a position intended to mimic a valgus collapse position described in the literature. For this study, the valgus collapse position consisted of 30° of knee flexion, internal rotation of the hip, and 10° of external tibial rotation. ACL length decreased significantly from full extension (30.2 ± 2.6 mm) to 30° of flexion (27.1 ± 2.2 mm). ACL length further decreased in the valgus collapse position (25.6 ± 2.4 mm). Both functional bundles of the ACL followed similar trends with regards to decreases in length in each of the three positions. Since strain would follow patterns of ACL length, landing on an extended knee may be a more relevant risk factor for ACL injuries than the valgus collapse position in males. Future studies should evaluate the effects of dynamic motion patterns on in vivo ACL strains.

Associação do valgo dinâmico do joelho no teste de descida de degrau com a amplitude de rotação medial do quadril

INTRODUÇÃO: O joelho corresponde a uma articulação muito estudada devido à alta incidência de lesões. Grande parte dos estudos correlaciona estas lesões com o valgo durante movimentos de flexão do joelho (dinâmico), que é atribuído principalmente ao fraco desempenho muscular do glúteo médio. OBJETIVO: Este estudo teve por objetivo avaliar a associação entre a rotação medial do quadril e o ângulo do valgo (bidimensional) durante o teste de descida do degrau, obtidos através da biofotogrametria (software SAPO). MÉTODOS: 104 voluntários, esportistas do sexo feminino, foram avaliados na mensuração da rotação interna de quadril (teste de Craig) e o valor angular do valgo do joelho durante a descida de degrau; as análises foram submetidas a confiabilidade interobservadores com o teste de concordância de Bland e Altman. Os dados foram analisados através de regressão linear múltipla de modo a ajustar os resultados pela idade dos avaliados. RESULTADOS: O ângulo gerado na rotação medial do quadril teve média de 45,3 graus, já o valgo do joelho durante o movimento de descer um degrau apresentou média de 8,6 graus. Foi encontrada relação inversa significativa na associação da rotação medial e o valgo do joelho. CONCLUSÃO: Os dados apresentados mostram uma possível associação entre a diminuição da rotação medial do quadril com o aumento do valgo do joelho, porem os dados não são conclusivos devido a avaliação ter sido bidimensional. Os resultados obtidos sugerem a necessidade de mais estudos conclusivos.

Sex-dimorphic landing mechanics and their role within the noncontact ACL injury mechanism: evidence, limitations and directions

Anterior cruciate ligament (ACL) injuries continue to present in epidemic-like proportions, carrying significant short- and longer-term debilitative effects. With females suffering these injuries at a higher rate than males, an abundance of research focuses on delineating the sex-specific nature of the underlying injury mechanism. Examinations of sex-dimorphic lower-limb landing mechanics are common since such factors are readily screenable and modifiable. The purpose of this paper was to critically review the published literature that currently exists in this area to gain greater insight into the aetiology of ACL injuries in females and males. Using strict search criteria, 31 articles investigating sex-based differences in explicit knee and/or hip landing biomechanical variables exhibited during vertical landings were selected and subsequently examined. Study outcomes did not support the generally accepted view that significant sex-based differences exist in lower-limb landing mechanics. In fact, a lack of agreement was evident in the literature for the majority of variables examined, with no sex differences evident when consensus was reached. The one exception was that women were typically found to land with greater peak knee abduction angles than males. Considering knee abduction increases ACL loading and prospectively predicts female ACL injury risk, its contribution to sex-specific injury mechanisms and resultant injury rates seems plausible. As for the lack of consensus observed for most variables, it may arise from study-based variations in test populations and landing tasks, in conjunction with the limited ability to accurately measure lower-limb mechanics via standard motion capture methods. Regardless, laboratory-based comparisons of male and female landing mechanics do not appear sufficient to elucidate causes of injury and their potential sex-specificity. Sex-specific in vivo joint mechanical data, if collected accurately, may be more beneficial when used to drive models (e.g., cadaveric and computational) that can additionally quantify the resultant ACL load response. Without these steps, sex-dimorphic landing mechanics data will play a limited role in identifying the aetiology of ACL injuries in women and men.