Drop-jump Landing Research Articles

Physiotherapists can identify female football players with high knee valgus angles during vertical drop jumps using real-time observational screening.

Clinical measurement, controlled laboratory study. To assess the relationships among real-time observational screening of frontal plane knee control and knee valgus angles and abduction moments calculated from 3-D motion analysis during a vertical drop jump. A secondary purpose was to investigate interrater agreement for 3 independent physiotherapists. Current approaches to screen for anterior cruciate ligament injury risk are based on complex biomechanical analyses or 2-dimensional video reviews. There is a need for simple and efficient, low-cost screening methods. Sixty Norwegian elite female football (soccer) players performed a vertical drop-jump task. Using real-time observational screening, 3 physiotherapists independently scored each participant's frontal plane knee control as good, reduced, or poor, based on specific criteria. Screening test scores were correlated to frontal plane knee kinematics and kinetics using 3-D motion analysis. Interrater agreement was determined using kappa correlation coefficients. Knee valgus angles differed significantly among players rated as having poor, reduced, or good knee control (10.3° ± 3.4°, 5.4° ± 4.1°, and 1.9° ± 4.3°, respectively). The correlation between the observation test scores and valgus angles was moderate for all raters (0.54-0.60, P≤.001), but the observation scores correlated poorly with abduction moments (0.09-0.11, P>.05). The highest discriminative accuracy was found for knee valgus angles across all raters (area under the receiver-operating-characteristic curve, 0.85-0.89). The interrater agreement between the physiotherapists was substantial to almost perfect, with percentage agreement and kappa coefficients ranging from 70% to 95% and 0.52 to 0.92, respectively. Physiotherapists can reliably identify female athletes with high knee valgus angles in a vertical drop-jump landing using real-time observational screening.

Risk Factors for Lower Extremity Injuries in Elite Female Soccer Players

Background: The incidence of lower extremity injuries in female soccer players is high, but the risk factors for injuries are unknown. Purpose: To investigate risk factors for lower extremity injuries in elite female soccer players. Study Design: Cohort study; Level of evidence, 3. Methods: Players in the Norwegian elite female soccer league (N = 12 teams) participated in baseline screening tests before the 2009 competitive soccer season. The screening included tests assessing maximal lower extremity strength, dynamic balance, knee valgus angles in a drop-jump landing, knee joint laxity, generalized joint laxity, and foot pronation. Also included was a questionnaire to collect information on demographic data, elite-level experience, and injury history. Time-loss injuries and exposure in training and matches were recorded prospectively in the subsequent soccer season using weekly text messaging. Players reporting an injury were contacted to collect data regarding injury circumstances. Univariate and multivariate regression analyses were used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for ±1 standard deviation of change. Results: In total, 173 players underwent complete screening tests and registration of injuries and exposure throughout the season. A total of 171 injuries in 107 players (62%) were recorded; ligament and muscle injuries were the most frequent. Multivariate analyses showed that a greater body mass index (BMI) (OR, 1.51; 95% CI, 1.21-1.90; P = .001) was the only factor significantly associated with new lower extremity injuries. A greater BMI was associated with new thigh injuries (OR, 1.51; 95% CI, 1.08-2.11; P = .01), a lower knee valgus angle in a drop-jump landing was associated with new ankle injuries (OR, 0.64; 95% CI, 0.41-1.00; P = .04), and a previous knee injury was associated with new lower leg and foot injuries (OR, 3.57; 95% CI, 1.27-9.99; P = .02), whereas none of the factors investigated influenced the risk of new knee injuries. Conclusion: A greater BMI was associated with lower extremity injuries in elite female soccer players. Clinical Relevance: Increased knowledge on risk factors for lower extremity injuries enables more targeted prevention strategies with the aim of reducing injury rates in female soccer players.

Changes in Drop-Jump Landing Biomechanics During Prolonged Intermittent Exercise

Background:As injury rates rise in the later stages of sporting activities, a better understanding of lower extremity biomechanics in the later phases of gamelike situations may improve training and injury prevention programs.Hypothesis:Lower extremity biomechanics of a drop-jump task (extracted from a principal components analysis) would reveal factors associated with risk of anterior cruciate ligament injury during a 90-minute individualized intermittent exercise protocol (IEP) and for 1 hour following the IEP.Study Design:Controlled laboratory study.Level of Evidence:Level 4.Methods:Fifty-nine athletes (29 women, 30 men) completed 3 sessions. The first session assessed fitness for an IEP designed to simulate the demands of a soccer match. An experimental session assessed drop-jump biomechanics, after a dynamic warm-up, every 15 minutes during the 90-minute IEP, and for 1 hour following the IEP. A control session with no exercise assessed drop-jump performance at the same intervals.Results:Two biomechanical factors early in the first half (hip flexion at initial contact and hip loading; ankle loading and knee shear force) decreased at the end of the IEP and into the 60-minute recovery period, while a third factor (knee loading) decreased only during the recovery period (P ≤ 0.05).Conclusion:The individualized sport-specific IEP may have more subtle effects on landing biomechanics when compared with short-term, exhaustive fatigue protocols.Clinical Relevance:Potentially injurious landing biomechanics may not occur until the later stages of soccer activity.

Clinical Assessment of Drop-Jump Landing for Determination of Risk for Knee Injury

Context:Clinical assessment tools are needed to identify individual athletes who possess elevated risk for anterior cruciate ligament injury. Existing methods require expensive equipment and the investment of a large amount of time for data processing, which makes them unfeasible for preparticipation screening of a large number of athletes.Objective:To assess the extent of agreement between LESS and the iLESS classifications of jump landing performance and the level of agreement between ratings assigned by a novice evaluator and an expert evaluator.Methods:Ratings of drop-jump landings from 20 video recordings of NCAA Division I collegiate athletes, which were randomly selected from a large database.Results:The dichotomous iLESS score corresponded to the dichotomous classification of LESS score for 15 of 20 cases rated by the expert evaluator and 17 of 20 cases rated by the novice evaluator. For the iLESS, only 2 scores out of 20 differed between the evaluators.Conclusions:A high level of agreement was observed between the LESS and iLESS methods for classification of jump- landing performance. Because the iLESS method is inexpensive and efficient, it may prove to be valuable for preparticipation assessment of knee injury risk.

Timing of Lower Extremity Frontal Plane Motion Differs Between Female and Male Athletes During a Landing Task

Background: Female athletes are at a greater risk for noncontact anterior cruciate ligament injuries than male athletes. Gender differences in frontal plane kinematics (hip adduction, knee valgus, and ankle eversion) and temporal relationships that make up the components of dynamic knee valgus may explain this discrepancy. Hypothesis: The authors hypothesized that women would reach peak frontal plane kinematic values earlier during landing compared with their male counterparts. Study Design: Controlled laboratory study. Methods: Hip, knee, and ankle 3-dimensional kinematics were measured using high-speed motion capture in 10 National Collegiate Athletic Association Division I female athletes and 10 male practice squad athletes during a drop-jump landing. Independent t tests were used to analyze each dependent variable to identify differences between genders. Results: Maximum hip adduction, knee valgus, and ankle eversion occurred earlier in women than in men (mean differences 33.7% of stance [95% CI, 20.2%-47.2%], 41.7% [95% CI, 31.5%-51.6%], 16.5% of stance [95% CI, 7.3%-25.6%], respectively). Maximum hip adduction and knee valgus occurred before maximum knee flexion in women and after in men (mean differences 0.11 seconds [95% CI, 0.05-0.18 seconds], 0.19 seconds [95% CI, 0.13-0.25 seconds], respectively). Maximum ankle eversion occurred earlier in women than in men (mean difference 0.06 seconds [95% CI, 0.01-0.11 seconds]). There was a significant difference between genders for angular velocity of knee valgus (mean difference = 25.53 deg/sec [95% CI, 8.30-42.77 deg/sec]). Conclusion: Frontal plane kinematic temporal relationships at the hip, knee, and ankle differ between genders. The components of dynamic knee valgus peak during the deceleration phase in women and during the acceleration phase in men during a drop-jump landing. These data suggest that men and women employ a completely different kinematic landing/jumping strategy and that women land and collapse very rapidly into valgus compared with their male counterparts. Clinical Relevance: The differences in timing of the components of dynamic knee valgus between women and men may contribute to the increased risk of noncontact anterior cruciate ligament injuries in female athletes. There may be implications for neuromuscular reeducation training in those at risk for anterior cruciate ligament injury so the components of dynamic valgus occur later in the landing phase of jumping.

Contribution of Knee Flexor and Extensor Strength on Sex-Specific Energy Absorption and Torsional Joint Stiffness During Drop Jumping

Lower extremity injury often occurs during abrupt deceleration when attempting to change the body's direction. Although sex-specific biomechanics have been implicated in the greater risk of acute knee injury in women than in men, it is unknown if sex differences in thigh strength affect sex-specific energy absorption and torsional joint stiffness patterns. To determine sex differences in energy absorption patterns and joint stiffnesses of the lower extremity during a drop jump and to determine if these sex differences were predicted by knee extensor and flexor strength. Cross-sectional study. Laboratory environment. Recreationally active, college-aged students (41 women: age = 22.1 ± 2.9 years, height = 1.63 ± 0.07 m, mass = 59.3 ± 8.0 kg; 40 men: age = 22.4 ± 2.8 years, height = 1.77 ± 0.1 m, mass = 80.9 ± 14.1 kg). Participants performed knee flexor and extensor maximal voluntary isometric contractions followed by double-leg drop-jump landings. Lower extremity joint energetics (J × N(-1) × m(-1)) and torsional joint stiffnesses (Nm × N(-1) × m(-1) × degrees(-1)) were calculated for the hip, knee, and ankle during the initial landing phase. Body weight was measured in newtons and height was measured in meters. Sex comparisons were made and sex-specific regressions determined if thigh muscle strength (Nm/kg) predicted sagittal-plane landing energetics and stiffnesses. Women absorbed 69% more knee energy and had 36% less hip torsional stiffness than men. In women, greater knee extensor strength predicted greater knee energy absorption (R(2) = 0.11, P = .04), and greater knee flexor strength predicted greater hip torsional stiffness (R(2) = 0.12, P = .03). Sex-specific biomechanics during the deceleration phase of a drop jump revealed that women used a strategy to attempt to decrease system stiffness. Additionally, only female strength values were predictive of landing energetics and stiffnesses. These findings collectively demonstrated that the task may have been more difficult for women, resulting in a different movement strategy among those with different levels of thigh strength to safely complete the task. Future researchers should look at other predictive factors of observed sex differences.

Joint Laxity Is Related to Lower Extremity Energetics during a Drop Jump Landing

To examine the relationships between anterior knee laxity (AKL), genu recurvatum (GR), and general joint laxity (GJL) with sagittal plane energetics in males and females during a drop jump task. A total of 68 females and 50 males were measured for AKL, GR, and GJL and were instrumented to obtain neuromuscular and biomechanical data on their dominant limb during the initial landing phase of a 45-cm drop jump. Multiple linear regressions determined the extent to which the three joint laxity variables combined to predict hip, knee, and ankle work absorption and stiffness. Associations between joint laxity and joint kinematics, joint kinetics, and muscle activation amplitudes were also investigated to further interpret significant relationships. Higher AKL and GJL and lower GR combined to predict greater knee work absorption (R2 = 0.210, P = 0.002) and stiffness (R2 = 0.127, P = 0.033) and lower ankle stiffness (R2 = 0.115, P = 0.048) in females. These associations were modulated through greater peak knee extensor moments and flexion angles, lower hamstring activation, and lower ankle extensor moments. In males, joint laxity had little impact on knee energetics, but a significant association was observed between greater GJL and decreased ankle stiffness (R2 = 0.209, P = 0.012), a product of both greater peak ankle flexion and decreased ankle extensor moment. Females with greater AKL and GJL and lower GR demonstrated a landing strategy that increased work absorption and stiffness about the knee, whereas females with greater GR demonstrated a landing style that reduced knee work absorption and stiffness. The findings suggest that AKL, GR, and GJL may represent distinct risk factors and support the need to consider more comprehensive laxity profiles as they relate to knee joint function and anterior cruciate ligament injury risk.

Frontal and Sagittal Plane Biomechanics During Drop Jump Landing in Boys Who Are Obese

To investigate the frontal and sagittal plane lower extremity biomechanics during drop jump landings in boys who were obese and boys who were of healthy weight. Twelve boys participated, 6 were considered as healthy weight (body mass index for age <85%, age 11.0 +/- 0.8 years), and 6 were considered as obese (body mass index for age >95%, age 12.1 +/- 0.7 years). Three-dimensional data were collected during landing from a drop jump. Group means were compared using Student t tests (alpha = 0.05). Significant differences were found in peak hip adduction moment, timing of peak dorsiflexion and knee flexion angles, and timing of peak knee extension and abduction moments. Boys who were obese exhibited significant differences in frontal and sagittal plane biomechanics when landing from a jump compared with healthy weight peers. These differences could place boys who are obese at greater risk for lower extremity injuries when they engage in jump-landing activities.

Reliability and Validity of Observational Risk Screening in Evaluating Dynamic Knee Valgus

Nonexperimental methodological study. To determine the interrater and intrarater reliability and validity of using observational risk-screening guidelines to evaluate dynamic knee valgus. A deficiency in the neuromuscular control of the hip has been identified as a key risk factor for noncontact anterior cruciate ligament (ACL) injury in postpubescent females. This deficiency can manifest itself as a valgus knee alignment during tasks involving hip and knee flexion. There are currently no scientifically tested methods to screen for dynamic knee valgus in the clinic or on the field. Three physiotherapists used observational risk-screening guidelines to rate 40 adolescent female soccer players according to their risk of ACL injury. The rating was based on the amount of dynamic knee valgus observed on a drop-jump landing. Ratings were evaluated for intrarater and interrater agreement using kappa coefficients. Sensitivity and specificity of ratings were evaluated by comparing observational ratings, with measurements obtained using 3-dimensional (3-D) motion analysis. Kappa coefficients for intrarater and interrater agreement ranged from 0.75 to 0.85, indicating that ratings were reasonably consistent over time and between physiotherapists. Sensitivity values were inadequate, ranging from 67% to 87%. This indicated that raters failed to detect up to a third of "truly high-risk" individuals. Specificity values ranged from 60% to 72%, which was considered adequate for the purposes of the screening. Observational risk screening is a practical and cost-effective method of screening for ACL injury risk. Rater agreement and specificity were acceptable for this method, but sensitivity was not. To detect a greater proportion of individuals at risk of ACL injury, coaches and clinicians should ensure that they include additional tests for other high-risk characteristics in their screening protocols.

Differences In Impact Force Attenuation And Knee Kinematics During Drop Jump And Drop Landing

Few studies have compared impact attenuation during a pure landing task when impact attenuation is the main goal to a drop jump task where impact attenuation is immediately followed by energy generation. PURPOSE: To examine differences of impact force attenuation between drop landing and the landing phase of a drop jump activity. METHODS: Seven NCAA football athletes (TRAINED) and 7 recreationally active students (REC) with limited sports training and prior experience in jumping sports, performed 5 drop landing trials from each of 3 landing heights: 40 cm, 60 cm and 100% of each individual's maximum jump height (100%MJH) and 5 drop jump trials from each of the 3 drop heights. Simultaneous recording of 3D kinematics and ground reaction force (GRF) were conducted at 240 Hz and 1200 Hz, respectively. Selected peak GRF and kinematic variables were evaluated using a mixed design 2 × 2 (group x height) repeated measures analysis of variance (ANOVA, p < 0.05) for the 40 and 60 cm conditions for the two activities separately. The group differences at the 100%MJH were evaluated with an independent-samples t-test. RESULTS: The results showed that the TRAINED participants had significantly smaller peak GRF (1.7 and 2.2 BW for 40 and 60 cm) and longer time to the peak (0.057 and 0.053 s for 40 and 60 cm) compared to the REC participants (2.0 and 2.7 BW, 0.050 and 0.048 s for 40 and 60 cm) in the landing phase of drop jump. However, the TRAINED participants had greater peak GRFs (2.7 and 3.5 BW for 40 and 60 cm) and significantly shorter times to the peak (0.048 and 0.043 s for 40 and 60 cm) compared to the REC participants (2.0 and 2.7 BW, 0.060 and 0.053 s for 40 and 60 cm) in drop landing. The TRAINED athletes also showed similar knee ranges of motion (ROM) in the landing phase during drop jump but smaller and non-significant knee ROMs (p = 0.051) in drop landing compared to the REC counterparts. CONCLUSIONS: The TRAINED athletes exhibited greater impact attenuation during the landing phase of drop jump but less impact attenuation during drop landing. This difference is related to the differences in the knee ROMs during the two different landing activities. The TRAINED athletes are able to tolerate greater impact force in the regular landing and absorb greater impact force during the landing phase to facilitate energy generation during the takeoff phase in drop jump.

Dynamic Valgus Alignment and Functional Strength in Males and Females During Maturation

Sex differences in dynamic measures have been established in physically mature populations. Gaining information on maturation's effect on dynamic performance measures implicated in injury risk may enable us to better design injury prevention programs. To examine sex differences in dynamic valgus alignment and triple-hop distance measures across maturational stages in males and females. A secondary purpose was to determine if a field test of strength and power predicts dynamic valgus alignment. Cross-sectional study. Laboratory. 157 young athletes (78 females, 79 males) aged 9 to 18 years. Subjects performed drop-jump landings and single-leg triple-hop tests as part of a broader injury screening. Maturational status was ascertained from self-report questionnaires and grouped according to Tanner stages 1 and 2 (MatGrp1), 3 and 4 (MatGrp2), and 5 (MatGrp3). Frontal-plane knee valgus displacement, which served as a measure of dynamic valgus alignment, and single-leg triple-hop distance were assessed. Males demonstrated less dynamic valgus alignment during drop jumps in the latter maturational stages (MatGrp1 = 13.1 degrees +/- 8.7 degrees , MatGrp2 = 9.0 degrees +/- 6.2 degrees , MatGrp3 = 9.2 degrees +/- 9.4 degrees ), whereas females increased dynamic valgus alignment throughout maturation (MatGrp1 = 11.5 degrees +/- 6.9 degrees , MatGrp2 = 12.8 degrees +/- 8.8 degrees , MatGrp3 = 15.5 degrees +/- 8.7 degrees ). Thus, in the more mature groups, males had less dynamic valgus alignment than females. Both males (MatGrp1 = 393.5 +/- 63.7 cm, MatGrp2 = 491.8 +/- 95.1 cm, MatGrp3 = 559.3 +/- 76.3 cm) and females (MatGrp1 = 360.3 +/- 37.1 cm, MatGrp2 = 380.1 +/- 44.3 cm, MatGrp3 = 440.0 +/- 66.2 cm) increased triple-hop distance, but males increased more. Within each subgroup of MatGrp and sex, triple-hop distance had no predictive ability for dynamic malalignment. When dynamic valgus alignment and strength were assessed, sex and maturational status displayed an interaction. However, functional strength did not predict degree of dynamic valgus alignment.

Anatomical Contributions of the Hip on Dynamic Knee Valgus

Increased two-dimensional knee valgus has been suggested to be predictive of lower extremity injury. Research suggests that structural hip anteversion may alter hip rotational motion, and increase the potential for inward collapse of the knee. PURPOSE: To examine the relationships between hip anteversion and hip range of motion, and hip range of motion and frontal plane knee valgus during a drop-jump landing. METHODS: Clinical measures of hip anteversion and hip internal (HIR) and external (HER) rotation range of motions were measured on the left lower extremity of 70 NCAA Division I athletes (39 M, 31 F: 19.3 ± 1.3 yrs, 172.1 ± 8.6 cm, 66.1 ± 11.0 kg) as part of a larger risk factor screening project. Two-dimensional frontal plane kinematic joint angles (initial knee valgus at landing and knee valgus excursion during landing) were then ascertained via video analysis during a 45cm drop-jump landing. The average of 3 trials for each variable was used for analysis. Separate step-wise linear regressions determined the extent to which hip anteversion predicted HIR and HER, and whether HIR and HER would in turn predict knee valgus angles during the drop-jump landing. RESULTS: Hip anteversion was a strong positive predictor of HIR (R=.575, R2=.330, P<.001) but a weak negative predictor of HER (R=−.273, R2=.075, P=.022). HIR was a significant predictor of initial knee valgus, explaining 13.5% of the variance (P=.002). The prediction equation for this model was initial knee valgus = 1.432+.274HIR. HIR and HER were significant predictors of knee valgus excursion, explaining 11.9% of the variance (P=.014) yielding a prediction model of knee valgus excursion=17.557+.267HIR-.398HER. CONCLUSIONS: Increased forward projection of the femoral neck (hip anteversion) may increase hip internal rotation while decreasing external rotation. These changes in hip range of motions may influence the orientation of the hip and the length-tension relationship of the surrounding muscles, and in part contribute to dynamic knee malalignments known to be predictive of lower extremity injury. Ongoing research is examining whether these anatomical differences reduce the muscular efficiency and force producing capabilities of the hip musculature during functional activities.

Effects of Gender and Foot-Landing Techniques on Lower Extremity Kinematics during Drop-Jump Landings

The purpose of this study was to assess kinematic lower extremity motion patterns (hip flexion, knee flexion, knee valgus, and ankle dorsiflexion) during various foot-landing techniques (self-preferred, forefoot, and rear foot) between genders. 3-D kinematics were collected on 50 (25 male and 25 female) college-age recreational athletes selected from a sample of convenience. Separate repeated-measures ANOVAs were used to analyze each variable at three time instants (initial contact, peak vertical ground reaction force, and maximum knee flexion angle). There were no significant differences found between genders at the three instants for each variable. At initial contact, the forefoot technique (35.79 degrees +/- 11.78 degrees ) resulted in significantly (p = .001) less hip flexion than did the self-preferred (41.25 degrees +/- 12.89 degrees ) and rear foot (43.15 degrees +/- 11.77 degrees ) techniques. At peak vertical ground reaction force, the rear foot technique (26.77 degrees +/- 9.49 degrees ) presented significantly lower (p = .001) knee flexion angles as compared with forefoot (58.77 degrees +/- 20.00 degrees ) and self-preferred (54.21 degrees +/- 23.78 degrees ) techniques. A significant difference for knee valgus angles (p = .001) was also found between landing techniques at peak vertical ground reaction force. The self-preferred (4.12 degrees +/- 7.51 degrees ) and forefoot (4.97 degrees +/- 7.90 degrees ) techniques presented greater knee varus angles as compared with the rear foot technique (0.08 degrees +/- 6.52 degrees ). The rear foot technique created more ankle dorsiflexion and less knee flexion than did the other techniques. The lack of gender differences can mean that lower extremity injuries (e.g., ACL tears) may not be related solely to gender but may instead be associated with the landing technique used and, consequently, the way each individual absorbs jump-landing energy.

Knee Valgus during Drop Jumps in National Collegiate Athletic Association Division I Female Athletes

Background Female athletes land from a jump with greater knee valgus and ankle pronation/eversion. Excessive valgus and pronation have been linked to risk of anterior cruciate ligament injury. A medially posted orthosis decreases component motions of knee valgus such as foot pronation/eversion and tibial internal rotation. Hypothesis We hypothesized a medial post would decrease knee valgus and ankle pronation/eversion during drop-jump landings in NCAA-I female athletes. Study Design Controlled laboratory study. Methods Knee and ankle 3-dimensional kinematics were measured using high-speed motion capture in 10 National Collegiate Athletic Association Division I female athletes during a drop-jump landing with and without a medial post. Analysis of variance was used to determine differences in posting condition, t tests were used to determine dominant-nondominant differences, and the Pearson correlation coefficient was used to determine relationships between variables. Results Significant differences were found for all measures in the posted condition. A medial post decreased knee valgus at initial contact (1.24°, P< .01) and maximum angle (1.21 °, P< .01). The post also decreased ankle pronation/eversion at initial contact (0.77°, P < .01) and maximum angle (0.95°, P = .039). Conclusion The authors have demonstrated a significant decrease in knee valgus and ankle pronation/eversion during a drop jump with a medial post placed in the athletes’ shoes. Clinical Relevance A medial post may be a potential means to decrease risk of anterior cruciate ligament injury.

Effects of Fatigue and Sex on Frontal Plane Knee Motion and Kinetic Characteristics During Drop-Jump Landing

Effects of Fatigue and Sex on Frontal Plane Knee Motion and Kinetic Characteristics During Drop-Jump Landing