Biomechanical differences between unilateral and bilateral landings from a jump: gender differences

Sex differences in knee abduction during landing: a systematic review

BACKGROUND

Females suffer injuries to the anterior cruciate ligament at rates significantly higher than males. Frontal plane knee motion and load have been identified as major risk factors for anterior cruciate ligament injury and in turn have been examined extensively.

METHODS

A systematic review of MEDLINE, CINHAL, and SportDISCUS was performed (1982-June 2010). Criteria for inclusion were the use of 3-dimensional analyses of frontal plane knee motion and moments during landing between males and females.

RESULTS

Twenty-seven studies met the inclusion criteria and were reviewed. Sixty-three percent of included studies identified sex differences in knee abduction when landing across a variety of landing conditions.

CONCLUSIONS

Females appear to land with increased knee abduction motion compared with males in most biomechanics studies.

The effect of short-term resistance training on hip and knee kinematics during vertical drop jumps

The purpose of this study was to determine the effect of a weight-bearing free weight resistance training program alone on knee flexion, hip flexion, and knee valgus during unilateral and bilateral drop jump tasks. Twenty-nine young adult females with previous athletic experience were randomly divided into a control (n = 16) and a resistance training (n = 13) groups. The resistance training group completed 8 weeks of lower extremity, weight-bearing exercises using free weights, whereas the control group did not train. A pre- and posttest was conducted to measure knee valgus, knee flexion, and hip flexion during unilateral (30 cm) and bilateral (60 cm) vertical drop jumps for maximum height. Joint angles were determined using 3-dimensional electromagnetic tracking sensors (MotionMonitor; Innovative Sports Training, Inc., Chicago, IL, USA). Initial training intensity for the bilateral squat was 50% of the subject's 1 repetition maximum (RM), which increased 5% each week to 85% during the final week. Sets and repetitions ranged from 2 to 4 and from 4 to 12, respectively. The training loads for all other exercises (lunge, step-up, unilateral squat, and Romanian deadlift) increased from 15RM to 6RM from the initial to the final week. A repeated measures analysis of variance was used to determine differences in the hip and knee joint angles. No significant differences for knee valgus and hip flexion measures were found between the groups after training; however, knee flexion angle significantly increased in the training group from the pretest (77.2 ± 4.1°) to posttest (83.2 ± 3.7°) during the bilateral drop jump. No significant changes occurred during the unilateral drop jump. Bilateral measures for knee flexion, hip flexion, and knee valgus were significantly (p < 0.05) greater than the unilateral measures during the drop jump task, which indicate an increased risk for anterior cruciate ligament (ACL) injury during unilateral drop jumps. The data support that the strength and conditioning specialist can implement resistance training alone during a short-term training period to reduce the risk of ACL injury by increasing knee flexion during a bilateral drop jump task. Increased knee flexion angles after resistance training may indicate a reduced risk for knee injury from improved neuromuscular control, resulting in a softer landing.

Comparison of landing knee valgus angle between female basketball and football athletes: possible implications for anterior cruciate ligament and patellofemoral joint injury rates

OBJECTIVE

To evaluate landing strategies of female football and basketball athletes with relation to possible injury mechanisms and disparity in injury.

DESIGN

Descriptive laboratory study.

PARTICIPANTS

52 female football players and 41 female basketball players.

MAIN OUTCOME MEASURES

Frontal plane projection angle (FPPA) was measured during the single leg land (SLL) and drop jump (DJ) screening tasks.

RESULTS

2 × 2 × 2 mixed factorial ANOVA showed significant main effects were observed for sport, whilst significant interaction effects were seen between sport and task. Females in both sports exhibited significantly greater FPPA values during the SLL task than the DJ task (p < 0.001). Basketball players demonstrated significantly greater FPPA values during SLL than football players (p < 0.001), whilst no differences were found between sports in the DJ task (p = 0.328).

CONCLUSION

Female basketball players display greater FPPA values during unilateral landing tasks than female football players which may reflect the greater ACL injury occurrence in this population. Injury prevention programs in these athletes should incorporate unilateral deceleration and landing tasks and should consider the specific injury mechanisms in each sport.

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.

Sex differences in proximal control of the knee joint

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

Ativação muscular do quadril e do joelho em duas aterrissagens realizadas por atletas do sexo masculino

OBJETIVO: Comparar a atividade muscular antes e após o contato com o solo entre as aterrissagens unilateral (AU) e bilateral (AB) em atletas do sexo masculino. PARTICIPANTES: Quinze atletas masculinos de voleibol sem sinais e sintomas de lesões nas extremidades inferiores (13 ± 1 ano, 1,70 ± 0,12m, 60 ± 12kg). MENSURAÇÕES:Os participantes realizaram dois saltos verticais, aterrissando unilateralmente e bilateralmente. A atividade mioelétrica do reto femoral (RF), bíceps femoral (BF), adutores de quadril (AQ) e a relação BF/RF foram comparados entre as duas aterrissagens e entre as fases caracterizadas por 100ms antes (PRE) e 100ms após (POS) o contato com o solo. RESULTADOS: Em ambas as aterrissagens, a ativação do RF foi maior na fase POS em relação à PRE. Na comparação entre as aterrissagens dentro da mesma fase não encontramos diferenças estatísticas. Apesar de o BF não ter apresentado diferenças entre as fases PRE e POS em cada aterrissagem, sua ativação foi maior na AU. Os AQ apresentaram maior ativação na fase POS durante a AU, no entanto não houve diferenças quando comparadas as duas aterrissagens. A relação BF/RF apresentou valores maiores em ambas as aterrissagens na fase PRE. No entanto, não encontramos diferenças entre as aterrissagens. CONCLUSÃO: Os resultados sugerem que cada músculo apresenta um papel diferente durante a fase de aterrissagem em homens. Enquanto que o RF possui como principal função a frenagem da articulação do joelho e do movimento descendente, caracterizada pelo aumento da ativação na fase pós-contato, o BF parece atenuar a tensão articular do joelho em atividades de maior impacto, mantendo-se mais ativo durante todo o ciclo da AU. Já a maior ativação dos AQ após o contato com solo na AU evidencia a importância da região lombo-pélvica na estabilização pélvica em situações de grande instabilidade. Estudos futuros são necessários para determinar os efeitos da ativação muscular apresentada na imposição de cargas mecânicas potencialmente lesivas no joelho em atletas do sexo masculino.

Does an in-season only neuromuscular training protocol reduce deficits quantified by the tuck jump assessment?

BACKGROUND

Female athletes are 4–6 times more likely to suffer an ACL injury than males in comparable sports. A link between landing biomechanics and ACL injury has led to the development of injury prevention focused training protocols. It is often difficult to measure the protocols’ efficacy of different protocols on reduction of ACL injury-related factors.

PURPOSE

The purpose of this study was to test the effects of in-season neuromuscular training on a field-based evaluation used to help identify athletes at risk for ACL injuries. The hypothesis was that the ACL injury prevention training program included with an in-season soccer program would demonstrate increased improvement in the Tuck Jump Assessment (TJA) scores at post-season follow-up testing relative to standard in-season soccer training.

METHODS

Forty-nine female soccer players were tested with TJA before and after participation in either in-season injury prevention training (IN) or standard in-season soccer training (CTRL). Participants were filmed performing the TJA with digital video cameras and scored by two separate raters, each viewing randomized videos. The groups received neuromuscular training synthesized from previous protocols demonstrated to decrease ACL injury. A mixed design (2X2; group by time) repeated measures ANOVA was used to test the interaction and main effects of group (ACL intervention training in-season vs. standard soccer in-season training) and time (pre vs. post-season) on dynamic TJA scores.

RESULTS

There was a significant main effect of time on TJA score (p=0.04) for athletes measured at pre- and post-season. The IN group reduced measured landing and jumping deficits from 5.4 ± 1.6 to 4.9 ± 1.0 points following training. CTRL showed a 14% reduction in TJA deficit points following the soccer season.

CONCLUSIONS

The tested hypothesis that the in-season ACL intervention training can be utilized to reduce measured TJA deficits above and beyond a standard in-season soccer protocol was not supported. Future research is warranted to determine if a combination of intensive pre-season and reduced in-season maintenance training is optimal for improvement of dynamic movement biomechanics during the TJA and ultimately preventing ACL injuries.

Time to stability differences between male and female dancers after landing from a jump on flat and inclined floors

OBJECTIVE

To determine the effect of gender and inclined floor on time to stability (TTS) after landing from a vertical jump.

DESIGN

This study used a repeated measures design with male and female professional dancers landing on a flat and 4 inclined floors. A repeated measures univariate analysis of variance (gender × floor) was performed on TTS in the anterior-posterior and medial-lateral directions.

SETTING

Biomechanics laboratory.

PARTICIPANTS

Twenty-three female and 13 male professional dancers.

INDEPENDENT VARIABLES

Gender and floor inclination (flat, posterior, anterior, lateral, and medial).

MAIN OUTCOME MEASURES

Time to stability in the anterior-posterior and medial-lateral directions after landing from a vertical jump.

RESULTS

Female dancers exhibited longer TTS in both directions (P ≤ 0.05). Floor inclination or the interaction of gender × floor did not have an effect on TTS (P > 0.3).

CONCLUSIONS

Female dancers exhibited longer TTS after landing from a vertical jump compared with their male counterparts. This balance difference may be a factor related to the higher rate of ankle sprain among female dancers. Additionally, professional dancers exhibited similar TTS when landing on flat and inclined floors.

The effects of single-leg landing technique on ACL loading

Anterior Cruciate Ligament (ACL) injury is one of the most serious and costly injuries of the lower extremity, occurring more frequently in females than males. Injury prevention training programs have reported the ability to reduce non-contact ACL injury occurrence. These programs have also been shown to alter an athletes' lower extremity position at initial contact with the ground and throughout the deceleration phase of landing. The purpose of this study was to determine the influence of single-leg landing technique on ACL loading in recreationally active females. Participants were asked to perform "soft" and "stiff" drop landings. A series of musculoskeletal models were then used to estimate muscle, joint, and ACL forces. Dependent t-tests were conducted to investigate differences between the two landing techniques (p<0.05). Instructing participants to land 'softly' resulted in a significant decrease in peak ACL force (p=0.05), and a significant increase in hip and knee flexion both at initial contact (IC) and the time of peak ACL force (F(PACL)). These findings suggest that altering landing technique using simple verbal instruction may result in lower extremity alignment that decreases the resultant load on the ACL. Along with supporting the findings of reduced ACL force with alterations in sagittal plane landing mechanics in the current literature, the results of this study suggest that simple verbal instruction may reduce the ACL force experienced by athletes when landing.

Gender and Foot Orthotic Device Effect on Frontal Plane Hip Motion During Landing From a Vertical Jump

Excessive hip motion has been linked to lower extremity pathology. Foot orthoses are commonly used to control motion within lower extremity joints when lower extremity pathology and dysfunction are present. Few studies have investigated the effect of foot orthoses on hip angular kinematics during functional activities. Eighteen females and 18 males performed a vertical jump with and without a prefabricated foot orthoses to determine the biomechanical effect of foot orthoses on hip kinematics when landing from a jump. Data collection included three-dimensional motion analysis of the lower extremity. Pairedttests were performed to determine if differences existed within genders with and without foot orthoses. At the hip joint, there was significantly less hip adduction motion in the foot orthoses condition as compared with the no foot orthoses condition in females (p< .05). There were no differences between foot orthoses conditions in males. Females appear to have a different proximal response to foot orthoses when landing from a forward jump than males.

Biomechanics laboratory-based prediction algorithm to identify female athletes with high knee loads that increase risk of ACL injury

OBJECTIVE

Knee abduction moment (KAM) during landing predicts non-contact anterior cruciate ligament (ACL) injury risk with high sensitivity and specificity in female athletes. The purpose of this study was to employ sensitive laboratory (lab-based) tools to determine predictive mechanisms that underlie increased KAM during landing.

METHODS

Female basketball and soccer players (N=744) from a single county public school district were recruited to participate in testing of anthropometrics, maturation, laxity/flexibility, strength and landing biomechanics. Linear regression was used to model KAM, and logistic regression was used to examine high (>25.25 Nm of KAM) versus low KAM as surrogate for ACL injury risk.

RESULTS

The most parsimonious model included independent predictors (β±1 SE) (1) peak knee abduction angle (1.78±0.05; p<0.001), (2) peak knee extensor moment (0.17±0.01; p<0.001), (3) knee flexion range of motion (0.15±0.03; p<0.01), (4) body mass index (BMI) Z-score (-1.67±0.36; p<0.001) and (5) tibia length (-0.50±0.14; p<0.001) and accounted for 78% of the variance in KAM during landing. The logistic regression model that employed these same variables predicted high KAM status with 85% sensitivity and 93% specificity and a C-statistic of 0.96.

CONCLUSIONS

Increased knee abduction angle, quadriceps recruitment, tibia length and BMI with decreased knee flexion account for 80% of the measured variance in KAM during a drop vertical jump.

CLINICAL RELEVANCE

Females who demonstrate increased KAM are more responsive and more likely to benefit from neuromuscular training. These findings should significantly enhance the identification of those at increased risk and facilitate neuromuscular training targeted to this important risk factor (high KAM) for ACL injury.

An investigation of lower extremity energy dissipation strategies during single-leg and double-leg landing based on sagittal and frontal plane biomechanics

There is limited understanding of the differences in lower extremity energy dissipation strategies between single-leg and double-leg landing maneuvers. This study sought to investigate these differences in sagittal and frontal planes, and explain the differences using kinematics and kinetics. We hypothesized that single-leg and double-leg landing maneuvers involve different lower extremity energy dissipation strategies in both planes. Ten recreational athletes were recruited and instructed to perform double-leg and single-leg landing from 0.60-m height. Force-plates and motion-capture system were used to obtain kinetics and kinematics data respectively. Joint power was taken as product of joint moment and angular velocity. Joint work was computed as integral of joint power over time, whereby negative work represented energy dissipation. In the sagittal plane, the hip and knee showed major contributions to energy dissipation during double-leg landing; the hip and ankle were the dominant energy dissipaters during single-leg landing. In the frontal plane, the hip acted as the key energy dissipater during double-leg landing; the knee contributed the most energy dissipation during single-leg landing. The knee also exhibited greater frontal plane joint ROM, moment and energy dissipation during single-leg landing than double-leg landing. Our findings indicated that different energy dissipation strategies were adopted for double-leg and single-leg landing in sagittal and frontal planes. Considering the prominent frontal plane biomechanics exhibited by the knee during single-leg landing, we expect that this maneuver may have greater likelihood of leading to traumatic knee injuries, particularly non-contact ACL injuries, compared to the double-leg landing maneuver.

The influence of sex and maturation on landing biomechanics: implications for anterior cruciate ligament injury

During landing and cutting, females exhibit greater frontal plane moments at the knee (internal knee adductor moments or external knee abduction moments) and favor the use of the knee extensors over the hip extensors to attenuate impact forces when compared with males. However, it is not known when this biomechanical profile emerges. The purpose of this study was to compare landing biomechanics between sexes across maturation levels. One hundred and nineteen male and female soccer players (9-22 years) participated. Subjects were grouped based on maturational development. Lower extremity kinematics and kinetics were obtained during a drop-land task. Dependent variables included the average internal knee adductor moment and sagittal plane knee/hip moment and energy absorption ratios during the deceleration phase of landing. When averaged across maturation levels, females demonstrated greater internal knee adductor moments (0.06±0.03 vs 0.01±0.02 N m/kg m; P<0.005), knee/hip extensor moment ratios (2.0±0.1 vs 1.4±0.1 N m/kg m; P<0.001) and knee/hip energy absorption ratios (2.9±0.1 vs 1.96±0.1 N m/kg m; P<0.001) compared with males. Higher knee adductor moments combined with disproportionate use of knee extensors relative to hip extensors observed in females reflect a biomechanical pattern that increases anterior cruciate ligament loading. This biomechanical strategy already was established in pre-pubertal female athletes.

Differences in time-frequency representation of lower limbs myoelectric activity during single and double leg landing in male athletes

This study compared the instantaneous median frequency (IMF) obtained by means of a Choi-Williams transform of an electromyogram of the lower-limb muscles during single-leg (SL) and double-leg (DL) landings performed by fifteen male athletes. The IMF values of the rectus femoris (RF), biceps femoris (BF) and hip adductors (HA) were compared between two landing tasks, within each landing, and before and after ground contact (GC). The IMF values of the RF did not change between landings in contrast to those of the BF, which presented from 20- to 40-ms higher SL values before GC and from 40 to 60 ms after GC. HA presented higher SL values during the 40-60 ms range before GC. Within each landing, the RF IMF decreased from 40 ms to 60 ms after GC in the SL. Similar results were found for the HA IMF, which decreased from 40ms to 80 ms after GC. The BF IMF showed no significant change. These results suggest muscle recruitment related to anterior cruciate ligament protection since the IMF values of the RF decreased in the SL, whereas the BF IMF increased. Results for the HA showed the importance of hip muscles in stabilizing the core region, allowing the activation of distal muscles with greater safety.

Gender Comparisons between Unilateral and Bilateral Landings

The increased number of women participating in sports has led to a higher knee injury rate in women compared with men. Among these injuries, those occurring to the ACL are commonly observed during landing maneuvers. The purpose of this study was to determine gender differences in landing strategies during unilateral and bilateral landings. Sixteen male and 17 female recreational athletes were recruited to perform unilateral and bilateral landings from a raised platform, scaled to match their individual jumping abilities. Three-dimensional kinematics and kinetics of the dominant leg were calculated during the landing phase and reported as initial ground contact angle, ranges of motion (ROM) and peak moments. Lower extremity energy absorption was also calculated for the duration of the landing phase. Results showed that gender differences were only observed in sagittal plane hip and knee ROM, potentially due to the use of a relative drop height versus the commonly used absolute drop height. Unilateral landings were characterized by significant differences in hip and knee kinematics that have been linked to increased injury risk and would best be classified as “stiff” landings. The ankle musculature was used more for impact absorption during unilateral landing, which required increased joint extension at touchdown and may increase injury risk during an unbalanced landing. In addition, there was only an 11% increase in total energy absorption during unilateral landings, suggesting that there was a substantial amount of passive energy transfer during unilateral landings.

Development and validation of a clinic-based prediction tool to identify female athletes at high risk for anterior cruciate ligament injury

BACKGROUND

Prospective measures of high knee abduction moment (KAM) during landing identify female athletes at high risk for anterior cruciate ligament injury. Laboratory-based measurements demonstrate 90% accuracy in prediction of high KAM. Clinic-based prediction algorithms that employ correlates derived from laboratory-based measurements also demonstrate high accuracy for prediction of high KAM mechanics during landing.

HYPOTHESES

Clinic-based measures derived from highly predictive laboratory-based models are valid for the accurate prediction of high KAM status, and simultaneous measurements using laboratory-based and clinic-based techniques highly correlate.

STUDY DESIGN

Cohort study (diagnosis); Level of evidence, 2.

METHODS

One hundred female athletes (basketball, soccer, volleyball players) were tested using laboratory-based measures to confirm the validity of identified laboratory-based correlate variables to clinic-based measures included in a prediction algorithm to determine high KAM status. To analyze selected clinic-based surrogate predictors, another cohort of 20 female athletes was simultaneously tested with both clinic-based and laboratory-based measures.

RESULTS

The prediction model (odds ratio: 95% confidence interval), derived from laboratory-based surrogates including (1) knee valgus motion (1.59: 1.17-2.16 cm), (2) knee flexion range of motion (0.94: 0.89°-1.00°), (3) body mass (0.98: 0.94-1.03 kg), (4) tibia length (1.55: 1.20-2.07 cm), and (5) quadriceps-to-hamstrings ratio (1.70: 0.48%-6.0%), predicted high KAM status with 84% sensitivity and 67% specificity (P < .001). Clinic-based techniques that used a calibrated physician's scale, a standard measuring tape, standard camcorder, ImageJ software, and an isokinetic dynamometer showed high correlation (knee valgus motion, r = .87; knee flexion range of motion, r = .95; and tibia length, r = .98) to simultaneous laboratory-based measurements. Body mass and quadriceps-to-hamstrings ratio were included in both methodologies and therefore had r values of 1.0.

CONCLUSION

Clinically obtainable measures of increased knee valgus, knee flexion range of motion, body mass, tibia length, and quadriceps-to-hamstrings ratio predict high KAM status in female athletes with high sensitivity and specificity. Female athletes who demonstrate high KAM landing mechanics are at increased risk for anterior cruciate ligament injury and are more likely to benefit from neuromuscular training targeted to this risk factor. Use of the developed clinic-based assessment tool may facilitate high-risk athletes' entry into appropriate interventions that will have greater potential to reduce their injury risk.

Clinical correlates to laboratory measures for use in non-contact anterior cruciate ligament injury risk prediction algorithm

BACKGROUND

Prospective measures of high knee abduction moment during landing identify female athletes at high risk for non-contact anterior cruciate ligament injury. Biomechanical laboratory measurements predict high knee abduction moment landing mechanics with high sensitivity (85%) and specificity (93%). The purpose of this study was to identify correlates to laboratory-based predictors of high knee abduction moment for use in a clinic-based anterior cruciate ligament injury risk prediction algorithm. The hypothesis was that clinically obtainable correlates derived from the highly predictive laboratory-based models would demonstrate high accuracy to determine high knee abduction moment status.

METHODS

Female basketball and soccer players (N=744) were tested for anthropometrics, strength and landing biomechanics. Pearson correlation was used to identify clinically feasible correlates and logistic regression to obtain optimal models for high knee abduction moment prediction.

FINDINGS

Clinical correlates to laboratory-based measures were identified and predicted high knee abduction moment status with 73% sensitivity and 70% specificity. The clinic-based prediction algorithm, including (Odds Ratio: 95% confidence interval) knee valgus motion (1.43:1.30-1.59 cm), knee flexion range of motion (0.98:0.96-1.01 degrees ), body mass (1.04:1.02-1.06 kg), tibia length (1.38:1.25-1.52 cm) and quadriceps to hamstring ratio (1.70:1.06-2.70) predicted high knee abduction moment status with C statistic 0.81.

INTERPRETATION

The combined correlates of increased knee valgus motion, knee flexion range of motion, body mass, tibia length and quadriceps to hamstrings ratio predict high knee abduction moment status in female athletes with high sensitivity and specificity.

CLINICAL RELEVANCE

Utilization of clinically obtainable correlates with the prediction algorithm facilitates high non-contact anterior cruciate ligament injury risk athletes' entry into appropriate interventions with the greatest potential to prevent injury.

The effect of fatigue on landing biomechanics in single-leg drop landings

OBJECTIVE

To examine the effects of fatigue on landing biomechanics in single-leg drop landings.

DESIGN

Quasi-experimental.

SETTING

Controlled research laboratory.

PARTICIPANTS

Twenty-four healthy individuals (12 women and 12 men).

INTERVENTIONS

Participants performed 3 single-leg drop landings from a height of 0.36 m before and after a fatiguing protocol.

MAIN OUTCOME MEASURES

Sagittal ankle flexion, sagittal knee flexion, and frontal knee valgus angles (degrees) at initial ground contact; vertical ground reaction forces (N); and time to stabilization (TTS) were compared between sexes and before (pre) and after (post) the fatiguing protocol.

RESULTS

After fatigue, participants landed with greater knee flexion [P = 0.001; pre 142.58 (14.35) degrees; post 136.12 (14.48) degrees] and ankle plantar flexion [P = 0.012; pre 79.04 (6.96) degrees; post 80.78 (6.13) degrees], and higher peak vertical ground reaction forces (P = 0.002; pre 2202.5 (536.29) N to post 2537.86 (469.66) N] but did not show changes in frontal knee angles [P = 0.815; pre, 7.94 (3.74) degrees; post, 8.08 (4.33) degrees]. Participants had higher anterior-posterior TTS [P = 0.021; pre 1.73 (0.53) seconds to post 1.93 (0.53) seconds] and vertical TTS [P = 0.002; pre 0.65 (0.24) seconds to post 0.93 (0.37) seconds] with a significant interaction noted in medial-lateral TTS [P = 0.043; pre 1.49 (0.64) seconds to post 1.61 (0.67) seconds]. No significant sex differences existed across any of the examined variables.

CONCLUSIONS

When landing after fatigue, participants had greater knee and ankle flexion angles at initial contact, had greater peak ground reaction forces, and required longer times to stabilize the body after landing, regardless of sex. Overall, fatigue clearly affects lower body biomechanics during single-leg landings. Whether these changes actually increase injury risk during activity warrants further investigation.

Sagittal knee joint kinematics and energetics in response to different landing heights and techniques

Single-leg and double-leg landing techniques are common athletic maneuvers typically performed from various landing heights during intensive sports activities. However, it is still unclear how the knee joint responds in terms of kinematics and energetics to the combined effects of different landing heights and techniques. We hypothesized that the knee displays greater flexion angles and angular velocities, joint power and work in response to the larger peak ground reaction force from 0.6-m height, compared to 0.3-m height. We further hypothesized that the knee exhibits elevated flexion angles and angular velocities, joint power and work during double-leg landing, relative to single-leg landing. Ground reaction force, knee joint kinematics and energetics data were obtained from 10 subjects performing single-leg and double-leg landing from 0.3-m to 0.6-m heights, using motion-capture system and force-plates. Higher peak ground reaction force (p<0.05) was observed during single-leg landing and/or at greater landing height. We found greater knee flexion angles and angular velocities (p<0.05) during double-leg landing and/or at greater landing height. Elevated knee joint power and work were noted (p<0.05) during double-leg landing and/or at greater landing height. The knee joint is able to respond more effectively in terms of kinematics and energetics to a larger landing impact from an elevated height during double-leg landing, compared to single-leg landing. This allows better shock absorption and thus minimizes the risk of sustaining lower extremity injuries.

Foot orthotic devices decrease transverse plane motion during landing from a forward vertical jump in healthy females

The use of foot orthoses has been evaluated during a variety of functional activities. Twelve college-aged active females wore two types of foot orthoses and performed a vertical jump to determine the biomechanical effect of the orthoses on lower extremity transverse plane movement during landing. Data collection included three-dimensional analysis of the tibia, knee, and hip. A repeated-measures ANOVA was performed to determine the differences between no orthoses, over-the-counter, and custom-made orthoses with transverse plane motion. At the hip joint, there was significantly less internal rotation (p < .05) in the over-the-counter condition as compared with the no orthoses condition. There was significantly less tibial internal rotation (p < .05) in the custom-made condition as compared with no orthoses. Over-the-counter devices decreased transverse plane motion at the hip, whereas custom-made devices decreased transverse plane motion of the tibia.

Limited hip and knee flexion during landing is associated with increased frontal plane knee motion and moments

BACKGROUND

It has been proposed that female athletes who limit knee and hip flexion during athletic tasks rely more on the passive restraints in the frontal plane to deceleration their body center of mass. This biomechanical pattern is thought to increase the risk for anterior cruciate ligament injury. To date, the relationship between sagittal plane kinematics and frontal plane knee motion and moments has not been explored.

METHODS

Subjects consisted of 58 female club soccer players (age range: 11-20 years) with no history of knee injury. Kinematics, ground reaction forces, and surface electromyography were collected while each subject performed a drop landing task. Subjects were divided into two groups based on combined sagittal plane knee and hip flexion angles during the deceleration phase of landing (high flexion and low flexion).

FINDINGS

Subjects in the low flexion group demonstrated increased knee valgus angles (P=0.02, effect size 0.27), increased knee adductor moments (P=0.03, effect size 0.24), decreased energy absorption at the knee and hip (P=0.02, effect size 0.25; and P<0.001, effect size 0.59), and increased vastus lateralis EMG when compared to subjects in the high flexion group (P=0.005, effect size 0.35).

INTERPRETATION

Female athletes with limited sagittal plane motion during landing exhibit a biomechanical profile that may put these individuals at greater risk for anterior cruciate ligament injury.

Differences in kinematics of single leg squatting between anterior cruciate ligament-injured patients and healthy controls

Seventy to eighty percent of all anterior cruciate ligament (ACL) injuries are due to non-contact injury mechanisms. It has been reported that the majority of injuries due to single leg landing come from valgus positioning of the lower leg. Preventing valgus positioning during single leg landing is expected to help reduce the number of ACL injuries. We found that many ACL-deficient patients cannot perform stable single leg squatting. Therefore, we performed 3D motion analysis of the single-legged half squat for ACL-injured patients to evaluate its significance as a risk factor for ACL injuries. We evaluated the relative angles between the body, thigh, and lower leg using an electromagnetic device during single leg half squatting performed by 63 ACL-injured patients (32 males, 31 females) the day before ACL reconstruction and by 26 healthy control subjects with no knee problems. The uninjured leg of ACL-injured male subjects demonstrated significantly less external knee rotation than that of the dominant leg of the male control. The uninjured leg of ACL-injured female subjects demonstrated significantly more external hip rotation and knee flexion and less hip flexion than that of the dominant leg of the female control. Comparing injured and uninjured legs, the injured leg of male subjects demonstrated significantly less external knee and hip rotation, less knee flexion, and more knee varus than that of the uninjured leg of male subjects. The injured leg of female subjects demonstrated more knee varus than that of the uninjured leg of female subjects. Regarding gender differences, female subjects demonstrated significantly more external hip rotation and knee valgus than male subjects did in both the injured and uninjured legs (P < 0.05). The current kinematic study exhibited biomechanical characteristics of female ACL-injured subjects compared with that of control groups. Kinematic correction during single leg half squat would reduce ACL reinjury in female ACL-injured subjects.

Comparison of landing biomechanics between male and female professional dancers

BACKGROUND

The incidence of anterior cruciate ligament injuries among dancers is much lower than that among team sport athletes and no clear gender disparity has been reported in the dance population. Although numerous studies have observed differences in lower extremity landing biomechanics between male and female athletes, there is currently little research examining the landing biomechanics of male and female dancers. Comparing landing biomechanics within this population may help explain the lower overall anterior cruciate ligament injury rates and the lack of gender disparity.

HYPOTHESIS

Due to the fact that dancers receive jump-specific and balance-specific training from a very young age, we hypothesized that there would be no gender differences in drop-landing biomechanics in professional dancers.

STUDY DESIGN

Controlled laboratory study.

METHODS

Kinematics and ground-reaction forces were recorded as 33 professional modern and ballet dancers (12 men and 21 women) performed single-legged drop landings from a 30-cm platform. Joint kinematics and kinetics were compared between genders.

RESULTS

No gender differences in joint kinematics or kinetics were found during landings (multivariate analysis of variance: P = .490 and P = .175, respectively). A significant relationship was found between the age at which the dancers began training and the peak hip adduction angle during landing (r = .358, P = .041).

CONCLUSION

In executing a 30-cm drop landing, male and female dancers exhibited similar landing strategies and avoided landing patterns previously associated with increased injury rates.

CLINICAL RELEVANCE

Commonly reported biomechanical differences between men and women, as well as the gender disparity among athletes in the incidence of ACL injuries, may be the result of inadequate experience in proper balance and landing technique rather than intrinsic gender factors. Beginning jump-specific and balance-specific training at an early age may counteract the potentially harmful adaptations in landing biomechanics observed in female athletes after maturity.

Regression relationships of landing height with ground reaction forces, knee flexion angles, angular velocities and joint powers during double-leg landing

Ground reaction forces (GRF), knee flexion angles, angular velocities and joint powers are unknown at large landing heights, which are infeasible for laboratory testing. However, this information is important for understanding lower extremity injury mechanisms. We sought to determine regression relationships of landing height with these parameters during landing so as to facilitate estimation of these parameters at large landing heights. Five healthy male subjects performed landing tasks from heights of 0.15-1.05 m onto a force-plate. Motion capture system was used to obtain knee flexion angles during landing via passive markers placed on the lower body. An iterative regression model, involving simple linear/exponential/natural logarithmic functions, was used to fit regression equations to experimental data. Peak GRF followed an exponential regression relationship (R(2)=0.90-0.99, p<0.001; power=0.987-0.998). Peak GRF slope and impulse also had an exponential relationship (R(2)=0.90-0.96, p<0.001; power=0.980-0.997 and R(2)=0.90-0.99, p<0.001; power=0.990-1.000 respectively) with landing height. Knee flexion angle at initial contact and at peak GRF had an inverse-exponential regression relationship (R(2)=0.81-0.99, p<0.001-p=0.006; power=0.834-0.978 and R(2)=0.84-0.97, p<0.001-p=0.004; power=0.873-0.999 respectively). There was also an inverse-exponential relationship between peak knee flexion angular velocity and landing height (R(2)=0.86-0.96, p<0.001; power=0.935-0.994). Peak knee joint power demonstrated a substantial linear relationship (R(2)=0.98-1.00, p<0.001; power=0.990-1.000). The parameters analyzed in this study are highly dependent on landing height. The exponential increase in peak GRF parameters and the relatively slower increase in knee flexion angles, angular velocities and joint power may synergistically lead to an exacerbated lower extremity injury risk at large landing heights.

Biomechanical characteristics of the knee joint in female athletes during tasks associated with anterior cruciate ligament injury

This study was designed to compare biomechanical characteristics of the knee joint for several athletic tasks to elucidate their effects and to examine what tasks pose a risk for ACL injury. Three athletic tasks were performed by 24 female athletes: single-limb landing, plant and cutting, and both-limb jump landing. Angular displacements of flexion/extension, abduction/adduction, and external/internal tibial rotation were calculated. Angular excursion and the rate of excursion of abduction and internal tibial rotation were also calculated. During plant and cutting, from foot contact, subjects rotated the tibia more rapidly and to a greater degree toward internal tibial rotation. Moreover, excursion of knee abduction is greater than that during single-limb landing. During both-limb jump landing, the knee flexion at foot contact was greater than for either single-limb landing or plant and cutting; peak knee abduction was greater than for either single-limb landing or plant and cutting. In plant and cutting, the risk of ACL injury is increased by greater excursion and more rapid knee abduction than that which occurs in single-limb landing, in addition to greater internal tibial rotation. Although single-limb tasks apparently pose a greater risk for ACL injury than bilateral landings, both-limb landing with greater knee abduction might also risk ACL injury.

Patellar tendon strain is increased at the site of the jumper's knee lesion during knee flexion and tendon loading: results and cadaveric testing of a computational model

BACKGROUND

Patellar tendinopathy (jumper's knee) is characterized by localized tenderness of the patellar tendon at its origin on the inferior pole of the patella and a characteristic increase in signal intensity on magnetic resonance imaging at this location. However, it is unclear why the lesion typically occurs in this area of the patellar tendon as surface strain gauge studies of the patellar tendon through the range of motion have produced conflicting results.

HYPOTHESIS

The predicted patellar tendon strains that occur as a result of the tendon loads and patella-patellar tendon angles (PPTAs) experienced during a jump landing will be significantly increased in the area of the patellar tendon associated with patellar tendinopathy.

STUDY DESIGN

Descriptive laboratory study.

METHODS

A 2-dimensional, computational, finite element model of the patella-patellar tendon complex was developed using anatomic measurements taken from lateral radiographs of a normal knee. The patella was modeled with plane strain rigid elements, and the patellar tendon was modeled with 8-node plane strain elements with neo-Hookean material properties. A tie constraint was used to join the patellar tendon and patella. Patella-patellar tendon angles corresponding to knee flexion angles between 0 degrees and 60 degrees and patellar tendon strains ranging from 5% to 15% were used as input variables into the computational model. To determine if the location of increased strain predicted by the computational model could produce isolated tendon fascicle damage in that same area, 5 human cadaveric patella-patellar tendon-tibia specimens were loaded under conditions predicted by the model to significantly increase localized tendon strain. Pre- and posttesting ultrasound images of the patella-patellar tendon specimens were obtained to document the location of any injured fascicles.

RESULTS

Localized tendon strain at the classic location of the jumper's knee lesion was found to increase in association with an increase in the magnitude of applied patellar tendon strain and a decrease in the PPTA. The principal stresses and strains predicted by the model for this localized area were tensile and not compressive in nature. Applying the tendon strain conditions and PPTA predicted by the model to significantly increase localized strain resulted in disruption of tendon fascicles in 3 of the 5 cadaveric specimens at the classic location of the patellar tendinopathy lesion.

CONCLUSION

The localized increase in patellar tendon strain that occurs in response to the application of tendon loads and decreased PPTA could induce microdamage at the classic location of the jumper's knee lesion.

CLINICAL RELEVANCE

The association of decreasing PPTA with increasing localized tendon strain would implicate the role of knee-joint angle as well as tendon force in the etiopathogenesis of jumper's knee.

Altered force ratio in unanticipated side jumps after treadmill run

OBJECTIVE

The aim was to investigate the influence of a run at the individual anaerobic threshold (IAT) on postural control in jumps with an unanticipated change of direction.

HYPOTHESIS

Dynamic postural control is less affected by the run in trained athletes than in recreational ones.

DESIGN

: Controlled prospective cohort study with an intervention.

SETTING

Biomechanics laboratory.

PARTICIPANTS

A total of 18 female high-level handball and volleyball players, 16 female and 8 male recreational athletes, with a mean age of 21.7 +/-4.1 years.

INTERVENTIONS

In the jump test, the ball switch, hit above the force plate during a forward jump, triggers indicator lamps on either side. After landing on the dominant leg, a second jump 90 degrees sideways following a light signal or a stabilization in one-leg stance was required. Nine jumps (randomized order) were performed before and at 1, 5, 10, 15 and 20 min after a 30-min treadmill run at the IAT.

MAIN OUTCOME MEASUREMENTS

For the second jump, the ratio of the absolute values of the maximum forces in anteroposterior and mediolateral direction was calculated as a parameter of dynamic postural control in the change of direction.

RESULTS

In both groups, the force ratio increased significantly at 1 and 5 min after the treadmill run. The relative increase did not differ between groups. Dynamic postural control in transfer from a forward to a sideward jump was reduced after the run. Recovery occurred within 10 min.

CONCLUSIONS

This study shows that dynamic postural control in jumps with an unanticipated change of direction is influenced by fatigue. These findings could be used to develop training programs aimed at reducing lower limb injuries in high-level ball sport athletes. The preventive effects have to be evaluated in further studies.

Trunk and hip control neuromuscular training for the prevention of knee joint injury

This article provide evidences to outline a novel theory used to define the mechanisms related to increased risk of ACL injury in female athletes. In addition, this discussion will include theoretical constructs for the description of the mechanisms that lead to increased risk. Finally, a clinical application section will outline novel neuromuscular training techniques designed to target deficits that underlie the proposed mechanism of increased risk of knee injury in female athletes.