Influence of gender on hip and knee mechanics during a randomly cued cutting maneuver

Objective. To investigate gender differences in three-dimensional hip and knee joint mechanics in collegiate athletes during a randomly cued cutting maneuver.

Design. Three-dimensional kinematics and kinetics were collected on 24 collegiate soccer players (12 females and 12 males) while each performed the cutting maneuver. In order to create a randomly cued condition, subjects were signaled by a lighted target board that directed them to perform one of three tasks. Hip and knee joint mechanics were compared between genders using one-tailed t-tests.

Background. Female athletes have an anterior cruciate ligament injury rate that is larger than their male counterparts. Gender differences in hip and knee joint mechanics during a randomly cued cutting maneuver have not been previously reported.

Methods. Five randomly cued cutting trials were included in the analysis. Selected peak hip and knee joint angles and moments were measured during the first 40° of knee flexion across the stance phase.

Results. Females demonstrated significantly less peak hip abduction than did males. Otherwise, there were no gender differences in selected peak hip and knee joint kinematics and moments.

Conclusions. Male and female collegiate soccer players demonstrate similar hip and knee joint mechanics while performing a randomly cued cutting maneuver.

Relevance. Because it is known that females incur a greater number of anterior cruciate ligament injuries than males, it is of interest to identify gender differences in lower extremity mechanics when performing sport specific tasks. Understanding of these differences will contribute to the development of prevention training programs.     

The influence of gender on knee kinematics, kinetics and muscle activation patterns during side-step cutting

BACKGROUND: It has been suggested that gender differences in the performance of athletic maneuvers is a contributory factor with respect to the disproportionate incidence of non-contact anterior cruciate ligament injury in female athletes. The purpose of this study was to evaluate gender differences in knee joint kinematics, kinetics and muscle activation during a side-step cutting. METHODS: Three-dimensional kinematics, ground reaction forces (2400 Hz) and electromyographic activity (surface electrodes) were recorded during the early deceleration phase of side-step cutting in 30 healthy collegiate soccer players (15 male, 15 female). Gender differences in knee joint kinematics, peak moments, net joint moment impulse and average muscle EMG intensity were evaluated with one-tailed t-tests. FINDINGS: No differences in kinematics were found. However, when compared to males, females demonstrated a smaller peak knee flexor moment (1.4 (0.8) vs. 2.1 (0.8) Nm/kg, P = 0.05) and a greater knee adductor moment (0.43 (0.5) vs. 0.01 (0.3) Nm/kg, P < 0.01) during early deceleration. In addition, females displayed greater average quadriceps EMG intensity than males (191% vs. 151% maximum voluntary isometric contraction, P = 0.02). INTERPRETATION: In general, females experienced increased frontal plane moments and decreased sagittal plane moments during early deceleration. These differences are suggestive of an "at risk" pattern in that frontal plane support of the knee is afforded primarily by passive structures (including the anterior cruciate ligament). Furthermore, increased quadriceps activity and smaller net flexor moments may suggest less sagittal plane protection (i.e., increased tendency towards anterior tibial translation).     

Fatigue-related changes in stance leg mechanics during sidestep cutting maneuvers

BACKGROUND: The increased number of women participating in sports has been paralleled by a greater knee injury rate in women compared to men. Among these injuries, those occurring to the anterior cruciate ligament are commonly observed during sidestep cutting maneuvers. In addition, general fatigue appears to correlate with injuries to the passive structures during a game. The purpose of the study was to examine the fatigue-related changes in lower limb mechanics during a cutting maneuver in female athletes. METHODS: Twelve college female soccer players were recruited. Sidestep cutting maneuvers were performed prior to, and after a fatiguing exercise (60-min shuttle run). Fatigue state was evaluated by calculating power output from countermovement jumps performed before and after the shuttle run. Three-dimensional stance leg hip, knee and ankle kinematics and kinetics during the cutting task were calculated and reported as initial ground contact angle, ranges of motion and peak moments of the stance phase. Cutting maneuver stance leg mechanics were analyzed through repeated measures two-way ANOVAs (P<0.05). FINDINGS: Jumping power output decrements suggested fatigue was induced. Sagittal and frontal planes kinematics and kinetics of the cutting task did not change after fatigue. In the transverse plane, the hip, knee and ankle joints were more externally rotated at touchdown, and during stance the knee underwent greater internal rotation. INTERPRETATION: Increased knee internal rotation has potentially important implication for increased injury risk when combined with unexpected perturbation faced in a game. Also, the fact that the sub-maximal level of fatigue did not lead to greater dynamic changes suggests a possible threshold of fatigue before function is dramatically affected.     

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.     

Medial Foot Loading on Ankle and Knee Biomechanics

Background

The incidence of anterior cruciate ligament (ACL) injuries among females continues at disproportionate rates compared to males, with research indicating inconclusive multifactorial causality. Data from previous retrospective studies suggest an effect of abnormal foot and ankle bio-mechanics on pathology at the knee, including the ACL.

Objective

To determine if a relationship exists between plantar foot loading patterns during normal gait and high risk biomechanics purported to increase risk of ACL injury.

Methods

Dynamic barefoot plantar pressure distribution was measured on 33 female collegiate soccer players. Groups were divided according to their predominant gait loading pattern (medial or lateral). Three dimensional (3-D) motion analysis was conducted during drop vertical jumps to assess vertical ground reaction force and discrete angle and joint moment variables of the lower extremities.

Results

No significant differences occured in sagittal or coronal plane knee joint kinematics and kinetics between the medial and lateral loading groups.

Discussion

Dynamic foot and ankle biomechanics during gait do not appear to be related to lower extremity kinematics or kinetics during landing in collegiate female soccer players.

Conclusion

The exact cause of the abnormal differences in female landing biomechanics has not been irrefutably defined. This study suggests no effect of foot and ankle biomechanics exists on the landing mechanics of female soccer players.     

Lower extremity biomechanics during the landing of a stop-jump task

BACKGROUND: Literature shows that landing with great impact forces may be a risk factor for knee injuries. The purpose of this study was to examine the relationships among selected lower extremity kinematics and kinetics during the landing of a stop-jump task. METHODS: Landmark coordinates and ground reaction forces during a stop-jump task were collected. Lower extremity joint angles and resultants were reduced. Pearson correlation coefficients among selected lower extremity kinematics and kinetics were determined. FINDINGS: The hip flexion angular velocity at the initial foot contact had significant correlation with peak posterior and vertical ground reaction forces (r = -0.63, P < 0.001, r = -0.48, P < 0.001) during the landing of the stop-jump task. The knee flexion angular velocity at the initial foot contact also had significant correlation with peak posterior and vertical ground reaction force (r = -0.49, P < 0.001, r = -0.06, P < 0.001) during the landing of the stop-jump task. Peak proximal tibia anterior shear force and peak knee extension moment during landing of the stop-jump task had significantly correlation with the corresponding posterior and vertical ground reaction forces (r > 0.51, P < 0.001). INTERPRETATION: A large hip and knee flexion angles at the initial foot contact with the ground do not necessarily reduce the impact forces during the landing of the stop-jump task, but active hip and knee flexion motions do. Hip joint motion at the initial foot contact with the ground appears to be an important technical factor that affects anterior cruciate ligament loading during the landing of the stop-jump task.     

Don’t Peak Too Early: Evidence for an ACL Injury Prevention Mechanism of the 11+ Program

BackgroundThe 11+ program prevents anterior cruciate ligament (ACL) injuries in athletes through unknown mechanisms.PurposeThe aim of the current study was to evaluate the effects of The 11+ intervention program, performed by female soccer players during a single season, on the frequency of Early Peaks during athletic tasks.MethodsThree teams (69 players) of collegiate female soccer athletes (Divisions I and II) were recruited. Two teams (49 players) volunteered to perform The 11+ three times per week for one season (~22 weeks plus three weeks pre-season), and one team (20 players) served as controls. The athletes performed three repetitions of a cutting maneuver, side shuffle direction change, and forwards to backwards running direction change before and after the competitive season and were recorded using marker-based 3D motion capture. Knee valgus moment time series were calculated for each repetition with inverse kinematics and classified as either “Very Early Peak”, “Early Peak” or “other” using cluster analysis. The classification was based timing of the peak relative to the timing of ACL injuries. The effect of the intervention on the frequency of Very Early Peaks and Early Peaks was evaluated with a mixed Poisson regression controlling for the movement task and pre-season frequency.ResultsThe 11+ intervention reduced the frequency of Early Peak knee valgus moment in one intervention team (coefficient = -1.16, p = 0.004), but not the other (coefficient = -0.01, p = 0.977). No effect was observed on the frequency of Very Early Peak knee valgus moment.ConclusionsReduced frequency of knee valgus moment Early Peak during athletic tasks may explain the mechanism by which The 11+ program decreases risk of ACL injury. Prospective studies with a much larger sample size are required to establish a link between Early Peak knee valgus moments and risk of ACL injury.Level of evidence2b     

Influences of hip external rotation strength on knee mechanics during single-leg drop landings in females

BACKGROUND: To determine the influence of hip external rotation strength on kinematic and kinetic variables during single-leg drop landings. METHODS: Females were divided into strong and weak groups based on isometric hip external rotation strength and lower extremity flexion-extension and varus-valgus kinematics and kinetics were evaluated during single-legged 40 cm drop landings. FINDINGS: Hip external rotation strength had no effect on sagittal or frontal plane angular motion throughout the landing cycle at the hip and knee. The strong group generated a statistically significant decrease in the peak vertical ground reaction force and external knee flexor moment. The weak group produced a greater external knee adduction moment, net knee anterior shear joint reaction force, and a greater hip external adduction moment. INTERPRETATION: Subjects with greater hip and quadriceps/hamstring strength exhibited a significant decrease in the vertical ground reaction force and external knee adduction and flexor moments. Hip and knee strength appear to relate to differences in high risk landing strategies.     

Joint kinetics during Tai Chi gait and normal walking gait in young and elderly Tai Chi Chuan practitioners

BACKGROUND: Tai Chi Chuan is becoming a popular exercise among elders. This study measured the inter-segmental forces and moments at the lower extremity joints during a Tai Chi gait as compared to those during normal walking gait, in both apparently healthy young and elderly Tai Chi Chuan practitioners. METHODS: Three-dimensional inter-segmental joint reaction force and moment were computed using the Inverse Dynamic Approach based on the kinematics and ground reaction force measurements in a laboratory setting in six young (two females, mean age 28; SD 6 years) and six elderly (five females, mean age 72; SD 8 years) subjects who had previous training of Yang style Tai Chi Chuan. FINDINGS: The results showed significant gait differences in both age groups, with significantly smaller peak compressive forces, larger peak shear forces in the ankle, knee and hip joints, and larger peak moments in the knee and hip joints during Tai Chi gait as compared to normal gait. Moreover, the peak shear force was oriented more in the medial-lateral direction at the ankle and knee joints, and the peak moment was in the frontal plane at the knee and hip joints. The results also showed significant age differences, with significantly smaller peak shear forces in all three joints in the elderly group than in the young group during Tai Chi gait. INTERPRETATION: Tai Chi gait has an increased shear force and frontal plane torque at lower extremity joints than normal gait. The shear force at all three lower extremity joints during Tai Chi gait is lower in the elderly subjects than young subjects. This data suggest that, in Tai Chi Chuan training, elderly people with degenerative joint diseases in the lower extremity should use caution when practicing Tai Chi Chuan.     

The effect of an impulsive knee valgus moment on in vitro relative ACL strain during a simulated jump landing

BACKGROUND: We tested the hypothesis that impulsive compression, flexion and valgus knee moment loading during a simulated one-footed jump landing will significantly increase the peak relative strain in the anteromedial region of the anterior cruciate ligament compared with loading without the valgus moment. METHODS: Ten cadaveric knees [mean (SD) age: 67.9 (7.6) years; 5 males; 5 females] were mounted into a custom fixture to simulate a lower extremity impact loading of approximately 1600 N. Triaxial load cells monitored the 3D tibial and femoral impulsive force and moments at 2000 Hz, while 3D tibiofemoral kinematics were measured at 400 Hz. Pre-impact quadriceps, hamstring and gastrocnemius muscle forces were simulated using pretensioned steel cables. A differential variable reluctance transducer measured the relative strain in the anteromedial aspect of the anterior cruciate ligament. With the knee initially in 25 degrees flexion, 10 trials were conducted with the impulsive force directed 4 cm posterior to the knee joint center in the sagittal plane ("neutral" loading) to cause a flexion moment, 10 trials were conducted under a similar loading, but with the force directed 15 degrees lateral to the knee sagittal plane ("valgus" loading), and the 10 neutral loading trials were then repeated. A non-parametric Wilcoxon signed rank test was used to test the hypothesis using a P<0.05 significance level. FINDINGS: The peak normalized anterior cruciate ligament strain was 30% larger for the impulsive compression loading in valgus and flexion compared with an impulsive compression loading in isolated flexion (P<0.05). INTERPRETATION: Minimizing the abduction loading of the knee during a jump landing should help reduce anterior cruciate ligament strain during that maneuver.     

Changes in knee moments with contralateral versus ipsilateral cane usage in females with knee osteoarthritis

BACKGROUND: Conservative treatment for osteoarthritis often involves educating the patient in methods of decreasing the load transmitted through the diseased joint. The use of a cane is one such method and the correct placement of the cane with respect to an abnormal knee joint is crucial. The purpose of this study was to compare effects on knee moments of force of contralateral versus ipsilateral cane usage in female subjects with osteoarthritic knees. METHODS: A convenience sample of 14 subjects volunteered for this study. Subjects walked over force platforms while ground reaction force and three-dimensional kinematic data were captured using a Vicon 370 System. The subjects were tested walking: (a) unaided, (b) with ipsilateral cane, and (c) with contralateral cane. Inverse dynamics were employed to calculate temporal-spatial, kinematic and kinetic variables. Dependent variables included hip and knee frontal plane and sagittal plane moments of force, walking speed, cadence and stride length. Repeated measures ANOVA assessed differences among walking conditions. FINDINGS: Subjects walked significantly faster in the unaided gait condition owing to a higher cadence. Ipsilateral cane use resulted in significantly larger hip (versus contralateral P=0.018; versus unaided P=0.036) and knee (versus contralateral P=0.043; versus unaided P=0.030) frontal plane peak moments during gait. Contralateral cane placement was associated with the smallest peak knee abductor (P=<0.001) and flexor (P=<0.001) moments. Knee deformity (varus or valgus) did not have any significant effect on any variable possibly due to small sample size. INTERPRETATION: The results suggest that as is the case for the hip contralateral cane placement is the most efficacious for persons with knee osteoarthritis. In fact, no cane use may be preferable to ipsilateral cane usage as the latter resulted in the highest knee moments of force, a situation which may exacerbate pain and deformity.     

Sagittal plane biomechanics cannot injure the ACL during sidestep cutting

BACKGROUND: Knee joint sagittal plane forces are a proposed mechanism of anterior cruciate ligament injury during sport movements such as sidestep cutting. Ligament force magnitudes for these movements however, remain unknown. The need to examine injury-causing events suggests elucidation via model-based investigations is possible. Using this approach, the current study determined whether sagittal plane knee loading during sidestep cutting could in isolation injure the anterior cruciate ligament. METHODS: Experiments were performed on subject-specific forward dynamic musculoskeletal models, generated from data obtained from 10 male and 10 female athletes. Models were optimized to simulate subject-specific cutting movements. Random perturbations (n=5000) were applied to initial contact conditions and quadriceps/hamstrings activation levels to simulate their effect on peak 3D knee loads. Injury via the sagittal plane mechanism was based on the criterion of an anterior drawer force greater than 2000 N. FINDINGS: Realistic neuromuscular perturbations produced significant increases in external knee anterior force and valgus and internal rotation moments. Peak anterior drawer force never exceeded 2000 N in any model, and thus failed to cause anterior cruciate ligament injuries. Valgus loads reached values that were high enough to rupture the ligament, occurring more frequently in females than in males. INTERPRETATION: Sagittal plane knee joint forces cannot rupture the anterior cruciate ligament during sidestep cutting. The interaction between muscle and joint mechanics and external ground reaction forces in this plane, places a ceiling on ligament loads. Valgus loading is a more likely injury mechanism, especially in females. Modifying sagittal plane biomechanics will thus unlikely contribute to the prevention of anterior cruciate ligament injuries.     

Association between lower extremity posture at contact and peak knee valgus moment during sidestepping: implications for ACL injury

BACKGROUND. Knee valgus load during sports movement is viewed as an important predictor of non-contact anterior cruciate ligament injury risk, particularly in females. Formulating movement strategies that can reduce valgus loading during these movements therefore appears pertinent to reducing anterior cruciate ligament injury rates. With this in mind, the current study examined the relationship between peak valgus moment and lower extremity postures at impact during a sidestep cutting task. METHODS. Ten male and ten female NCAA athletes had initial contact three-dimensional hip, knee and ankle angles and subsequent knee valgus moment quantified during the execution of (n=10 trials) sidesteps. Peak valgus data were normalized to mass and height and tested for the main effect of gender (ANOVA, P<0.05). Intra-subject correlations between the eight initial joint angles and the normalized valgus moment were then conducted across the ten sidestepping trials. The ensuing slopes of regression were submitted to a two-sample t-test to determine whether mean slope values were significantly different from zero and for the main effect of gender (P<0.05). FINDINGS. Females had significantly larger normalized knee valgus moments than males. A greater peak valgus moment was associated with larger initial hip flexion and internal rotation, and with larger initial knee valgus angle. Peak knee valgus moment was more sensitive to initial hip internal rotation and knee valgus position in females. INTERPRETATION. Training of neuromuscular control at the hip joint may reduce the likelihood of anterior cruciate ligament injury via a valgus loading mechanism during sidestepping, especially in females.     

Comparison of landing maneuvers between male and female college volleyball players

OBJECTIVE: To compare differences in kinematic and kinetic parameters of knee, hip and ankle joints between male and female college volleyball players. DESIGN: Cross-sectional study. BACKGROUND: Landing injuries, which usually involve anterior cruciate ligament injuries, are common in volleyball with a higher incidence in females. Landing preferences of both male and female players may provide additional background about the mechanisms contributing to the anterior cruciate ligament injuries. METHODS: Eight female and eight male college volleyball players performed spike and block landings from 40 and 60 cm height platforms. Lower extremity joint kinetics and kinematics, and leg muscle strengths were recorded. RESULTS: Females demonstrated significantly lower knee and hip flexion angles compared to their male counterparts in knee flexion at 40 cm spike and hip flexion at 40 cm block landings. Group comparison also revealed that male players' peak knee extensor moment at 60 cm block landing was significantly different than female players. Additionally, female players applied significantly higher normalized ground reaction forces and males knee flexion angles and thigh muscle strength results positive and highly correlated but relation could not found in females. It is likely that females may not use their thigh muscles as effective as males in landing. CONCLUSION: Female volleyball players initiate different lower extremity mechanics during landings than that of males. RELEVANCE: Identifying the landing strategy differences between female and male college volleyball players may provide detailed perspective about the load distribution in lower extremity joints for determining major factors affecting the increased incidence of anterior cruciate ligament injuries in females.     

Biomechanical Changes During a 90º Cut in Collegiate Female Soccer Players With Participation in the 11+

BackgroundValgus collapse and high knee abduction moments have been identified as biomechanical risk factors for ACL injury. It is unknown if participation in the 11+, a previously established, dynamic warm-up that emphasizes biomechanical technique and reduces ACL injury rates, reduces components of valgus collapse during a 90º cut.Hypothesis/PurposeTo determine whether participation in the 11+ during a single soccer season reduced peak knee abduction moment and components of valgus collapse during a 90º cut in collegiate female soccer players.Study DesignProspective cohort studyMethodsForty-six participants completed preseason and postseason motion analysis of a 90º cut. During the season, 31 players completed the 11+ and 15 players completed their typical warm-up (control group). Peak knee abduction moment, components of valgus collapse (hip adduction, internal rotation, and knee abduction angles), and a novel measure of knee valgus collapse were analyzed with repeated-measures ANOVAs to determine differences between preseason and postseason. Smallest detectable change (SDC) and minimal important difference (MID) values were applied to contextualize results.ResultsThere was a significant main effect of time for non-dominant knee valgus collapse (p=0.03), but decreases in non-dominant knee valgus collapse only exceeded the SDC in the intervention team.ConclusionsClinically meaningful decreases in knee valgus collapse may indicate a beneficial biomechanical effect of the 11+. Participation in the 11+ may lower ACL injury risk by reducing valgus collapse during a 90º cut.Level of Evidence2b     

The influence of experience on knee mechanics during side-step cutting in females

BACKGROUND: It is thought that female athletes with limited experience in a sport perform athletic maneuvers differently than their more experienced counterparts, and that they do so in a manner that places them at greater risk for injury. The purpose of this study was to evaluate the influence of athletic experience on knee mechanics during the execution of a side-step cutting maneuver in young female athletes. METHODS: Three-dimensional kinematics, ground reaction forces and electromyographic activity (surface electrodes) were recorded during the early deceleration phase of side-step cutting in 30 high school females (15 experienced, 15 novice). Group differences in knee joint kinematics, peak moments, net joint moment impulse and average muscle activation were evaluated. FINDINGS: No significant group differences were found in knee kinematics. When compared to experienced females, novice females demonstrated significantly smaller flexor, adductor, and internal rotator peak moments and smaller net joint moment impulse in all three planes at the knee. No group differences were found for average EMG; however, novice athletes had significantly greater co-contraction at the knee. INTERPRETATION: The finding of smaller knee moments and greater muscle co-contraction in the novice group suggests that these athletes may adopt a protective strategy in response to a relatively unfamiliar task. In addition, these results suggest that increased moments at the knee emerge with experience, indicating that more skilled athletes may be at greater risk for anterior cruciate ligament (ACL) injury.     

Three-dimensional hip and knee kinematics during walking,running, and single-limb drop landing in females with and without genu valgum

BackgroundDynamic knee valgus in females has been associated with various knee pathologies. Abnormal 3D hip and knee kinematics contribute prominently to this presentation, and these may become more aberrant with more demanding tasks. Underlying genu valgus may also accentuate such kinematics, but this effect has never been tested. Therefore, the purpose of this study was to compare 3D hip and knee kinematics during walking, running, and single-limb drop landing in females with and without genu valgus malalignment. We expected abnormal kinematics to become more evident in the valgus subjects as task demands increased.MethodsEighteen healthy females with genu valgum and 18 female controls with normal alignment underwent 3D motion analysis while performing walking, running, and single-limb drop-landing trials. Sagittal, frontal, and transverse plane hip and knee kinematics were compared between groups across tasks using analyses of variance and between-group effect sizes.FindingsGroup differences did not generally increase with higher forces. The valgus females demonstrated decreased hip flexion (ES = 0.72–0.88) and increased knee abduction (ES = 0.87–1.47) across the tasks. During running and single-limb drop landing, they showed increased knee external rotation (ES = 0.69–0.73). Finally, during walking, the valgus females showed increased hip adduction (ES = 0.69).InterpretationThese results suggest that females with genu valgus alignment utilize aberrant hip and knee mechanics previously associated with dynamic valgus in the literature, but that these pathomechanics do not generally worsen with rising task demands. Healthy females that present with genu valgus may be natively at elevated risk for knee pathology.     

Whole body kinematics and knee moments that occur during an overhead catch and landing task in sport

BACKGROUND: Athletes suffering an anterior cruciate ligament injury tend to exhibit similar body postures that in sidestep cutting are associated with increased knee moments. This relationship, however, has not been investigated in landing. Catching a ball in different overhead positions may affect landing postures and knee joint moments. This study investigated these possible relationships. It was anticipated that some joint postures would be associated increased knee loads during the landing task. METHODS: Twenty-five healthy male team sports athletes performed four variations of a landing task. Full body kinematics were identified at initial contact. Peak flexion, valgus and internal rotation moments at the knee, measured during early landing, were normalized to mass and height and statistically compared. Intra-participant correlations were performed between all kinematics and each moment. Mean slopes for each correlation were used to identify the existence of relationships between full body kinematics and knee joint moments. Findings Landing after an overhead catch when the ball moved towards a player's support leg resulted in increased peak valgus moments. These increased valgus moments were correlated with increased knee flexion, hip flexion, and torso lean, as well as torso rotation towards the support leg, and foot and knee external rotation. Increased internal rotation moments were correlated with reduced hip abduction and external rotation, increased ankle inversion, knee external rotation and torso lean away from the support leg. Interpretation Learning to land with techniques that do not reflect postures associated with high knee moments may reduce an athlete's risk of non-contact anterior cruciate ligament injury.     

Frontal and transverse plane hip kinematics and gluteus maximus recruitment correlate with frontal plane knee kinematics during single-leg squat tests in women

Background

Hip muscle dysfunction may be associated with knee valgus that contributes to problems like patellofemoral pain syndrome. The purpose of this study was to (1) compare knee and hip kinematics and hip muscle strength and recruitment between “good” and “poor” performers on a single-leg squat test developed to assess hip muscle dysfunction and (2) examine relationships between hip muscle strength, recruitment and frontal plane knee kinematics to see which variables correlated with knee valgus during the test.

Methods

Forty-one active women classified via visual rating as “good” or “poor” performers on the test participated. Participants completed 5-repetition single-leg squat tests. Isometric hip extension and abduction strength, gluteus maximus and gluteus medius recruitment, and 3-dimensional hip and knee kinematics during the test were compared between groups and examined for their association with frontal plane knee motion.

Findings

“Poor” performers completed the test with more hip adduction (mean difference = 7.6°) and flexion (mean difference = 6.3°) than “good” performers. No differences in knee kinematics, hip strength or hip muscle recruitment occurred. However, the secondary findings indicated that increased medial hip rotation (partial r = 0.94) and adduction (partial r = 0.42) and decreased gluteus maximus recruitment (partial r = 0.35) correlated with increased knee valgus.

Interpretation

Whereas hip muscle function and knee kinematics did not differ between groups as we'd hypothesized, frontal plane knee motion correlated with transverse and frontal plane hip motions and with gluteus maximus recruitment. Gluteus maximus recruitment may modulate frontal plane knee kinematics during single-leg squats.     

Lower extremity kinetics during stair ambulation in patients with and without patellofemoral pain

Objective. To compare lower extremity kinetics during stair ascent and descent in subjects with and without patellofemoral pain.

Design. A cross-sectional study utilizing a control group.

Background. The patellofemoral joint reaction force (the resultant force between the quadriceps muscle force and patellar ligament force) increases with quadriceps force and knee flexion angle. Consequently, patients with patellofemoral pain may employ compensatory strategies to minimize pain and reduce patellofemoral joint reaction forces during activity.

Methods. 10 individuals with a diagnosis of patellofemoral pain and 10 individuals without pain participated. Subject groups were matched on sex, age, height, and body mass. Anthropometric data, three dimensional kinematics, and ground reaction forces were used to calculate lower extremity sagittal plane moments (inverse dynamics) while subjects ascended and descended stairs at a self-selected pace. Differences in kinetic variables between groups were assessed using 2×2 (group × stair condition) analysis of variance.

Results. Subjects with patellofemoral pain had decreased peak knee extensor moments during stair ascent and descent. There were no group differences in peak hip, ankle, or support moments, however, subjects with patellofemoral pain had decreased cadence (descent) compared to controls.

Conclusion. Subjects with patellofemoral pain had reduced peak knee extensor moments, suggesting that quadriceps avoidance was employed to reduce patellofemoral joint reaction forces. The lack of group differences in peak moments at the hip and ankle suggests that secondary compensation did not occur exclusively at the hip or ankle in this group of subjects with patellofemoral pain.Relevance statement

Because stair ambulation is often used to evaluate the reproducibility of symptoms and to identify abnormal movement patterns indicative of patellofemoral pain, knowledge of lower extremity mechanics during stair negotiation is necessary to better characterize compensatory behavior in this population.