Medial Knee Displacement Research Articles

Greater hip internal rotation range of motion is associated with increased dynamic knee valgus during jump landing, both before and after fatigue.

The aim of this study was to analyse sex-specific differences contributing to dynamic valgus in competitive soccer players before and after a standardised fatiguing protocol. Thirty-nine healthy female and male competitive soccer players (19 females and 20 males) were recruited for the purpose of this study. Bilateral medial knee displacement (MKD) was assessed during drop jump landings using a three-dimensional motion capture system before and after a standardised fatiguing protocol. In addition, all soccer players underwent clinical examinations, including rotational hip range of motion (ROM), isokinetic strength testing and magnetic resonance imaging (MRI) of the hip and knee. Sex-specific and fatigue-dependent differences were reported, and the influence of demographic, clinical and radiographic factors on MKD was analysed via multiple linear regression models. Compared with male soccer players, female soccer players demonstrated a tendency towards increased MKD during drop jump landings before (p = 0.09) and after the fatiguing protocol (p = 0.04). Sex-specific differences included increased hip internal rotation (IR) ROM, decreased hip external rotation (ER) strength and increased femoral torsion in females (all p < 0.002). According to the multiple linear regression models (stepwise method), increased hip IR ROM (90° of flexion) and the non-dominant leg remained the sole independent predictors of increased MKD during drop jump landings before (p < 0.01 and p = 0.02, respectively) and after fatigue (p < 0.01 and p < 0.01, respectively). An increase in hip IR ROM in females was linearly related to MKD after fatigue (R2 = 0.25; p < 0.01). Female soccer players exhibited increased dynamic valgus before and after fatigue, which is likely attributed to joint mobility, as well as muscular and anatomical differences, such as increased hip IR ROM, reduced hip ER strength and increased femoral torsion. In particular, females with increased hip IR ROM were more susceptible to effects of fatigue on MKD, which may increase their risk for anterior cruciate ligament injury. Level III.

Are physical fitness, a history of childbirth and injury history related to knee valgus in female Canadian Armed Forces members during a bodyweight overhead squat movement?

ObjectivesA history of childbirth is associated with musculoskeletal injury (MSKi) in female members of the Canadian Armed Forces (CAF). While previous injury and pregnancy impact knee kinematics, it is unclear...

Effect of Hind- and Fore-Foot Eversion on Positional and Rotational Displacement of the Knee in Standing Posture.

We investigated the effects of hindfoot and forefoot eversion on the knee's positional and rotational displacement, plantar pressure, and foot discomfort in a standing posture, beyond the traditional focus on external knee adduction moments (EKAM) in lateral wedge insoles. Twenty-six healthy participants underwent hindfoot eversion from 0 to 10 degrees in 2-degree increments, and forefoot eversion from 0 degrees to the hindfoot eversion angle in 2-degree increments in a standing posture. At each eversion angle, the knee's medial displacement, EKAM's moment arm decrease, plantar pressure changes, and foot discomfort were obtained and compared across varying angles. Both hindfoot-only and entire-foot eversion led to significant medial knee displacement and the EKAM's moment arm decrease, with more pronounced effects in entire-foot eversion. At each hindfoot eversion angle, increasing forefoot eversion resulted in significant medial knee displacement and EKAM's moment arm decrease. Lower leg rotations were not significantly affected in hindfoot-only eversion but displayed significant medial tilting and internal rotation in entire-foot eversion at specific combinations. Varying eversion angles significantly influenced the forefoot pressure, with heel pressure remaining unaffected. Notably, the lateral forefoot pressure increased significantly as the forefoot eversion angle increased, particularly at higher hindfoot eversion angles. Foot discomfort increased significantly with higher eversion angles, particularly in entire-foot eversion, and also increased significantly as the forefoot eversion angle increased at higher hindfoot eversion angles. Insole configurations incorporating 6-10 degrees of hindfoot eversion and 40-60% forefoot eversion of the hindfoot angle may offer optimized biomechanical support for knee osteoarthritis patients.

The Role of Dynamic Knee Valgus in Occurrence of Knee Injuries: A Review Study

Background and Aims Dynamic knee valgus, as a poor movement pattern, may increase the risk of injury in the knee joint. This condition, which is related to a deviation in the lower limb alignment, can cause serious damage to the knee joint during tasks such as jump-landing, especially when bearing weight. The present study aims to investigate the role of dynamic knee valgus (DKV) in occurrence of knee injuries. Methods This is a review study. A search was conducted for the related articles published in English or Persian using the keywords Dynamic Knee Alignment, Dynamic Knee Valgus, Knee Joint Kinematics, Medial Collapse, Medial Knee Displacement, Frontal Plane Knee Excursion, Projection Angle, Dynamic Lower Extremity Valgus and Knee Injury in Science Direct, Scopus, PEDro, Google Scholar, PubMed, SID, ISC, Medlib, MagIran and IranDoc databases published from 2005 to May 2021. Initial search yielded 230 articles. After examining their full texts, 67 related articles were remained. Finally, 34 articles in the field of the role of DKV in occurrence of common knee injuries were selected for the review. Results Most of the studies were conducted on women and young people (aged 16-25 years). The DKV cause knee injuries such as anterior cruciate ligament injury (21 studies), patellofemoral pain syndrome (7 studies), tibiofemoral osteoarthritis (4 studies) and patellofemoral osteoarthritis (one study) as well as other cases such as osteoarthritis of the inner knee, chronic pain injuries in the hip and knee joints, and cartilage injuries. Conclusion DKV, as a poor movement pattern, put a person at risk of lower limb injuries. Muscle imbalance, muscle weakness, and impairment in the static alignment and its effect on dynamic alignment are among the most important mechanisms of DKV. Due to the structural and biomechanical characteristics, the most injuries caused by DKV occur in women.

More than just a side effect: Dynamic knee valgus and deadbug bridging performance in youth soccer players and alpine skiers have similar absolute values and asymmetry magnitudes but differ in terms of the direction of laterality.

From a preventative perspective, leg axis and core stabilization capacities are important for soccer players and alpine skiers; however, due to different sport-specific demands, the role of laterality clearly differs and may result in functional long-term adaptations. The aims of this study are 1) to determine whether there are differences in leg axis and core stability between youth soccer players and alpine skiers and 2) between dominant and non-dominant sides, and 3) to explore the outcomes of applying common sport-specific asymmetry thresholds to these two distinct cohorts. Twenty-one highly trained/national-level soccer players (16.1years, 95% CI: 15.6, 16.5) and 61 alpine skiers (15.7years, 95% CI: 15.6, 15.8) participated in this study. Using a marker-based 3D motion capture system, dynamic knee valgus was quantified as the medial knee displacement (MKD) during drop jump landings, and core stability was quantified as the vertical displacement during deadbug bridging exercise (DBB displacement ). For the analysis of sports and side differences, a repeated-measures multivariate analysis of variance was used. For the interpretation of laterality, coefficients of variation (CV) and common asymmetry thresholds were applied. There were no differences in MKD or DBB displacement between soccer players and skiers or between the dominant and non-dominant sides, but there was an interaction effect side*sports for both variables (MKD: p = 0.040, η2 p = 0.052; DBB displacement : p = 0.025, η2 p = 0.061). On average, MKD was larger on the non-dominant side and DBB displacement laterality on the dominant side in soccer players, whereas this pattern was reversed in alpine skiers. Despite similar absolute values and asymmetry magnitudes of dynamic knee valgus and deadbug bridging performance in youth soccer players and alpine skiers, the effect on the direction of laterality was opposite even though much less pronounced. This may imply that sport-specific demands and potential laterality advantages should be considered when dealing with asymmetries in athletes.

Sex Difference in Lower-limb Electromyography and Kinematics when Using Resistance Bands during a Barbell Back Squat.

The aim of this study was to compare the muscle activity of the gluteus medius (GMe), gluteus maximus (GMa), biceps femoris (BF), vastus lateralis (VL), vastus medialis (VM) and erector spinae (ES) as well as medial knee displacement (MKD) while using varying stiffness resistance bands (red: 1.68 kg; black: 3.31 kg; gold: 6.44 kg) during a barbell back squat (BBS) among males and females. A total of 23 (females: 11) resistance trained people were recruited for this study. Muscle activity was measured using electromyography, and motion capture cameras tracked lower-limb kinematics and MKD. Three resistance bands were placed at the distal end of the femur while performing a BBS at their 85% repetition maximum (RM). Parametric and non-parametric statistical analyses were conducted with the alpha level of 0.05. The gold resistance band resulted in a smaller knee-width-index value (i.e., greater MKD) compared to other bands (p < 0.01). Males exhibited less MKD compared to females during the BBS for each resistance band (p = 0.04). Males produced greater VL activity when using the black and gold resistance bands during the BBS (p = 0.03). When using a gold resistance band, the GMe muscle activation was higher compared to other resistance bands (p < 0.01). VM muscle activity was reduced when using a gold resistance band compared to no band condition (p < 0.01). BF (p = 0.39) and ES (p = 0.88) muscle activity did not change when using different resistance bands. As a result, females may be at a biomechanical disadvantage when using resistance bands compared to males while performing the BBS hindering them from optimal performance.

Intervention for Better Knee Alignment during Jump Landing: Is There an Effect of Internally vs. Externally Focused Instructions?

Externally focused attention is known to induce superior results in the movement outcome, whereas focusing attention on the moving body (internal focus) causes conscious control and constrains action. The study investigated effects on knee trajectory and whole-body movement complexity when addressing knee alignment using externally (EF) vs. internally (IF) focused instructions. Young ski racers, n = 24 (12 male), performed landings with subsequent jumps to submaximal height. Movements were tracked and analyzed during the ground contact phase. Sets of jumps were executed without instruction (CON), followed by EF and IF instructions on knee alignment in a random order. Medial–lateral displacement of the knee in landing quantified task achievement, and whole-body principal component analysis was used to compute movement complexity. Knee alignment instructions led to a significantly lower medial knee displacement compared to CON (p = 0.001, ηp2 = 0.35). EF vs. IF did not reach significance. EF, as well as IF instructions increased the prominence of the first movement pattern (p = 0.01, ηp2 = 0.22) with a reduction of higher-order patterns (p = 0.002, W = 0.11), suggesting a strategy of freezing degrees of freedom. Both instructions addressing the movement form positively influenced knee displacement during landing, and both led to a freezing strategy, simplifying whole-body coordination.

Breaking new grounds in injury risk screening in soccer by deploying unsupervised learning with a special focus on sex and fatigue effects

ABSTRACT In injury prevention, a vertical drop jump (DJ) is often used for screening athletes at risk for injury; however, the large variation in individual movement patterns might mask potentially relevant strategies when analysed on a group-based level. Two movement strategies are commonly discussed as predisposing athletes to ACL injuries: a deficient leg axis and increased leg stiffness during landing. This study investigated the individual movement pattern of 39 female and male competitive soccer players performing DJs at rest and after being fatigued. The joint angles were used to train a Kohonen self-organising map. Out of 19,596 input vectors, the SOM identified 700 unique postures. Visualising the movement trajectories and adding the latent parameters contact time, medial knee displacement (MKD) and knee abduction moment allow identification of zones with presumably increased injury risk and whether the individual movement patterns pass these zones. This information can be used, e.g., for individual screening and for feedback purposes. Additionally, an athlete’s reaction to fatigue can be explored by comparing the rested and fatigued movement trajectories. The results highlight the ability of unsupervised learning to visualise movement patterns and to give further insight into an individual athlete’s status without the necessity of a priori assumptions.

The Lumbopelvic-Hip Complex Contribution During Lower Extremity Screening Tests in Elite Figure Skaters.

Figure skating requires power and stability for takeoff and landing from multirotational jumps and various on-ice skills. Repetitive forces may cause overuse injuries distally, making lumbopelvic-hip endurance, strength, and neuromuscular control imperative. To compare lumbopelvic-hip endurance and neuromuscular control in elite figure skaters between sexes and landing and nonlanding limbs using common screening tests. Cross-sectional study. US Olympic and Paralympic Training Center. Forty elite figure skaters (20 women, 20 men; age = 23.2 ± 4.3 years) performed the Y-balance test, single-legged squat (SLS), single-legged squat jump (SLSJ), and unilateral hip-bridge endurance test (40 right [R] landing limbs, length = 169.1 ± 12.2 cm). Normalized reach difference (% of leg length) and composite scores [(anterior + posteromedial + posterolateral)/(limb length × 3) × 100] were calculated for the Y-balance test. Skaters held the unilateral hip bridge until failure with a maximum allotted time of 120 seconds. They performed 5 SLSs and 5 SLSJs while barefoot with the contralateral limb held behind them to mimic a landing position. Both tests were scored by the number of times the patella moved medially to the first ray (medial knee displacement [MKD]). Multivariate analyses of variance with post hoc independent t tests were conducted between sexes and groups. Paired t tests were used to analyze limb differences. Women had a larger composite Y-balance score (R = 10.8% of leg length, P = .002; left = 10.5%, P = .001) and hip-bridge hold time (R = 26.4 seconds, P = .004; left = 28.2 seconds, P = .002) for both limbs compared with men. Men held the hip-bridge longer on their landing limb. Six skaters performed worse on their nonlanding limb during the SLS, and 11 skaters had no MKD with either the SLS or SLSJ. Women performed better on the Y-balance and unilateral hip bridge tests. Increased MKD for some skaters during the SLS and SLSJ may have indicated hip-abductor weakness. Understanding the proximal lumbopelvic-hip variables during takeoff and landing may elucidate contributing factors to distal overuse injuries.

Preliminary study on acute effects of an intervention to increase dorsiflexion range of motion in reducing medial knee displacement

BackgroundDynamic knee valgus, visually represented as medial knee displacement, is associated with anterior cruciate ligament injury. Recently, restrictions in ankle dorsiflexion range of motion have been associated with medial knee displacement. Therefore, interventions potentially increasing ankle dorsiflexion range of motion could alleviate medial knee displacement. The purpose of this pilot study was to explore the acute effects of an intervention to increase ankle dorsiflexion range of motion and reduce medial knee displacement in individuals who display medial knee displacement that is corrected with a heel lift. MethodsEight young participants who displayed medial knee displacement corrected with a heel lift completed a single-session intervention aimed at increasing dorsiflexion range of motion. Immediately before and after the intervention session, dorsiflexion range of motion in three static conditions (passive straight-knee, passive bent-knee, and weight-bearing lunge) and medial knee displacement during an overhead squat were assessed. FindingsThe single-session training program increased participants' dorsiflexion range of motion in all three static conditions (p = 0.0005 for straight-knee, 0.02 for bent-knee, and 0.01 for lunge) with moderate to large effect sizes (0.55–1.18). Additionally, the training resulted in a significant reduction in medial knee displacement during the overhead squat (p = 0.02). InterpretationThe finding indicate that our interventional protocol appears beneficial in increasing dorsiflexion range of motion among individuals with medial knee displacement. Additionally, improving dorsiflexion range of motion may be a promising direction for reducing medial knee displacement, which is a risk factor for anterior cruciate ligament injury.

Lumbopelvic-Hip Complex Contribution During Lower Extremity Screening Tests in Elite Figure Skaters.

Figure skating requires power and stability for take-off and landing from multi-rotational jumps and various on-ice skills. Repetitive forces may cause overuse injuries distally making lumbopelvic-hip endurance, strength, and neuromuscular control imperative. The purpose was to compare lumbopelvic-hip endurance and neuromuscular control in elite figure skaters between sex and limbs using common screening tests. Cross-sectional study. U.S. Olympic and Paralympic Training Center. Forty elite figure skaters (23.2±4.3 years, 169.1±12.2 cm, 20F, 40R landing limb) performed the Y-balance test, single leg squat (SLS), single leg squat jump (SLSJ), and unilateral hip bridge endurance test. Normalized reach difference (% of leg length) and composite scores (((Anterior + Posteromedial + Posterolateral)/Limb length x 3) x100) were calculated for Y-balance test. Skaters held the unilateral hip bridge until failure with a maximum allotted time of 120s. Participants performed 5 SLS and SLSJ, barefooted with the contralateral limb held behind them to mimic a landing position. Both tests were scored by the number of times the patella moved medially to the first ray (medial knee displacement (MKD)). MANOVA with post-hoc independent t-tests were performed between groups and sex. Paired t-tests were used to analyze limb differences. Females had a larger composite Y-balance score (R:+10.8, p=.002; L:+10.5, p=.001) and hip bridge hold time (R:+26.4 sec, p=.004; L:+28.2 sec, p=.002) on both limbs compared to males. Males held the hip bridge longer on their landing limb. During the SLS and SLSJ, 6 skaters performed worse on their non-landing limb during the SLS, and 11 skaters had no MKD with either test. Females performed better on the Y-balance and unilateral hip bridge tests. Increased MKD for some skaters in the SLS and SLSJ may indicate hip abductor weaknesses. Understanding proximal lumbopelvic-hip variables during take-off and landing may elucidate contributing factors to distal overuse injuries.

Thigh muscle activation patterns and dynamic knee valgus at peak ground reaction force during drop jump landings: Reliability, youth competitive alpine skiing-specific reference values and relation to knee overuse complaints

Objectives(1) To evaluate the reliability of quantifying thigh muscle activation patterns and dynamic knee valgus during drop jump landings, (2) to provide reference values for female and male youth alpine skiers, and (3) to study their associations with age, anthropometrics, biological maturation and knee overuse complaints. DesignCross-sectional biomechanical experiment including questionnaires. MethodsOne hundred fourteen skiers of the under 16 category (main experiment) and twelve healthy participants (reliability experiment) volunteered. Quadriceps-to-hamstring-activation ratio and medial knee displacementat peak ground reaction force during drop jump landings were measured using marker-based motion analysis, force plates and electromyography. Additionally, age, anthropometrics, biological maturation and knee overuse complaints were assessed. ResultsThere were good test–retest reliabilities and moderate standardized typical errors for both quadriceps-to-hamstring-activation ratio (intraclass correlation coefficient(3,1) = 0.84 [95% confidence interval: 0.69, 0.94]; standardized typical errors = 0.43 [0.35, 0.56]) and medial knee displacement (intraclass correlation coefficient(3,1) = 0.87 [0.74, 0.95]; standardized typical errors = 0.39 [0.32, 0.50]). Male skiers had a significantly higher quadriceps-to-hamstring-activation ratio (3.9 ± 2.0 vs. 2.9 ± 1.4, p = 0.011), whilst medial knee displacement was comparable to females (12 mm ± 11 mm vs. 13 mm ± 9 mm; p = 0.419). In male skiers, medial knee displacement correlated with anthropometrics and maturity offset; in female skiers, quadriceps-to-hamstring-activation ratio and medial knee displacement were associated with knee overuse complaints (p < 0.05). ConclusionsFemale and male youth skiers use different thigh muscle activation strategies, but show comparable dynamic knee valgus motions during drop jump landings. In females, a combination of increased relative quadriceps activity and medial knee displacement may favour knee overuse complaints.

Electromyographic and kinematic analysis of females with excessive medial knee displacement in the overhead squat

Dynamic knee valgus is a multi-planar motion that has been associated with anterior cruciate ligament injuries and patellofemoral pain syndrome. Clinical assessment of dynamic knee valgus is usually performed through visual appearance of medial knee displacement (MKD) during the overhead squat. The aim of this study is to identify the kinematic and neuromuscular parameters associated with MKD. Twenty-two females performed an overhead squat and were assigned to the control group (n = 14) or the MKD group (n = 8). Electromyography and kinematic data of the lower extremity were collected. We observed MKD to exhibit greater muscle activity in the following muscles: adductor magnus, biceps femoris, vastus lateralis and vastus medialis muscles during the eccentric phase of the overhead squat. No group differences were observed during the concentric phase. Regarding the kinematics, the MKD group showed higher knee internal rotation and, knee abduction and ankle abduction, compared to controls. The combined information from the muscle activity results and kinematics of squat helps to explain the occurrence of excessive medial knee displacement and, hence, providing relevant information for health professionals to address this injury risk factor.

New Machine Learning Approach for Detection of Injury Risk Factors in Young Team Sport Athletes.

The purpose of this article is to present how predictive machine learning methods can be utilized for detecting sport injury risk factors in a data-driven manner. The approach can be used for finding new hypotheses for risk factors and confirming the predictive power of previously recognized ones. We used three-dimensional motion analysis and physical data from 314 young basketball and floorball players (48.4% males, 15.72±1.79 yr, 173.34±9.14 cm, 64.65±10.4 kg). Both linear (L1-regularized logistic regression) and non-linear methods (random forest) were used to predict moderate and severe knee and ankle injuries (N=57) during three-year follow-up. Results were confirmed with permutation tests and predictive risk factors detected with Wilcoxon signed-rank-test (p<0.01). Random forest suggested twelve consistent injury predictors and logistic regression twenty. Ten of these were suggested in both models; sex, body mass index, hamstring flexibility, knee joint laxity, medial knee displacement, height, ankle plantar flexion at initial contact, leg press one-repetition max, and knee valgus at initial contact. Cross-validated areas under receiver operating characteristic curve were 0.65 (logistic regression) and 0.63 (random forest). The results highlight the difficulty of predicting future injuries, but also show that even with models having relatively low predictive power, certain predictive injury risk factors can be consistently detected.

Return to sports following ACL reconstruction: prospective analysis of functional stability 3 months postoperatively in 280 patients

Introduction:For the last years, the terms return to play and return to competition after ACL reconstruction have been spread. Recent literature does not provide sufficient information on the approach to identify knee joint conditions that are likely to result in a recurrent injury following ACL reconstruction. Aim of this study is therefore to prospectively investigate the functional stability after ACL reconstruction by one single surgeon 3 months postoperatively.Hypotheses:The functional stability after ACL reconstruction 3 months postoperatively can safely be assessed using a multi-factorial testing analysis.Methods:All patients of the year 2018 diagnosed with a primary ACL instability and treated by one single surgeon were enrolled and prospectively assessed. Follow-up at 12 weeks postoperatively was performed using a functional “return-to-sports” analysis including isokinetic and isometric strength measurement (quad/ham ratio, BTE-primus), postural stability tests (MTF balance score), tapping test (force plate, Bertec) and a 3d-motion analysis (myomotion, Noraxon) during bilateral drop jumps and single leg hop tests (uni- and bilateral drop-jump, bilateral Counter Movement-Jump, Single-Leg Hop for Distance). Agility was assessed using speed chase (Speedcort system, Globalspeed). Jump height and distance were recorded by infra-red measuring device (Optogait, Microgate, Italy). Motion analysis to determine the quality of landing and jumping mechanisms using a real time 3d-avatar (myomotion, Noraxon) were investigated during a speedcourt and jump analysis. Contributed to the early time onset of functional analysis, any abnormalty in the bilateral jump tests or refusal of the jump test by the patient led to non-performance to the jump test with the postoperative leg. Statistical analysis were performed using a Wilcoxon-Rank-Sum-Test (p<0.05).Results:At analylsis date of 404 primary ACL reconstruction of the year 2018 a total of 324 patients particated in the functional analysis at three months postoperatively. During the “return-to-sports” no giving way symptoms or recurrent instability was to be recorded. BMI was 25,3 (+/-4,1) and 25,9 (+/-3,7) for female and male patients, respectively. Approximately 40% of all patients were able to perfom single legged jump tests. Three months postoperatively, the perfomance of the ACL reconstructed knee was significantly lower than the intact contralateral leg. Isometric and isokinetic strength analysis showed significantly lower peak maximal force for quadriceps and hamstrings compared to the intact contralateral side. No significant differences were seen in the analysis of the postural stability analysis. Even though the contact forces were significantly different between the intact leg and the postoperative leg, there was no significant differences between the quantitate analysis of the jump height and distance in the dimensions jumping and agility. As a parameter of functional valgus instability the medial knee displacement according to Krosshaug et al. 2016 was severely high, however there was no statistical significant difference to the intact leg.Conclusion:This study shows that a functional analysis at an early timepoint following ACL reconstruction reveals high abnormalities with regard to the quality of the landing mechanism. To further contribute to the high number of recurrent instabilities in the young athlete below 20 years of age, this may be crucial to intervene avoiding a medial knee displacement. To accomplish this, all patients were supported with specific training-protocols for further rehabilitation of the lower extremity. These protocols were individually set-up, however in nearly all patients a specific emphasize was on strengthening of the hip external rotators.

Objective visualization of the effect of different knee flexion angles on medial-lateral displacement of the knee center in frontal plane during single-Leg Squat

Introduction:The subjective single-leg squat (SLS) test can be used as a functional diagnostic agent to prevent knee injuries. [1] However, there are missing objective data about its functional rating, performance, squat depth and medio-lateral knee displacement in the frontal plane. [2] There-fore, the purpose of this pilot study was to evaluate the medio-lateral knee displacement in the frontal plane with a 3D motion capture system at different knee flexion angles during the SLS in healthy patients.Hypotheses:The hypothesis was that according to different knee flexion angles, there is a variability of medial knee displacement (= valgus positions) in healthy patients.Methods:17 healthy and sporty subjects (9 ♀/ 8 ♂, age 25±4 years, BMI 24±2 kg/m2) participated in this study. Exclusion criteria were balance disorders, hip knee and/ or ankle complaints, sur-gery history, high deviation in lower extremity axis (i.e. Genu varum/ Genu valgus). Knee dis-placement was measured by 3D motion analysis system (Vicon Motion Systems, Oxford, UK) using a modified method of Krosshaug et al. [3] Thus, knee displacement was defined as distance between knee joint center and reference plane including the calculated hip and ankle joint center and the fixed toe marker on the second metatarsal head. A positive knee dis-placement was associated with a knee valgus, a knee varus was described as negative knee displacement. Every participant did 12 single-leg squats on each side.Results:The following knee flexion angles of all SLSs were captured (°, mean and standard deviation (±)): start position at 11 ± 6; downward phase at 40 ± 0 and 60 ± 0; maximum at 86 ± 16; up-ward phase at 60 ± 0 and 40 ± 0; end position at 8 ± 6. The medio-lateral knee displacement of all SLSs showed at the mentioned knee flexion an-gles the following values respectively (mm, median, interquartile range (25th - 75th quartile)): -12 (-19 to -5); 0 (-9 to 7); 13 (-2 to 28); 38 (8 to 61); 17 (0 to 36); 4 (-6 to 16); -15 (-22 to -7).Conclusion:According to different knee flexion angles, there is a variability of medio-lateral knee dis-placements in healthy patients. This variability should be included in the functional rating of a SLS as well as in the interpretation of different knee pathologies. Moreover, it provides an objective basis in the prediction of knee injuries.

Postural control is altered in females with excessive medial knee displacement

ABSTRACT Knee valgus motion observed during landing tasks has been proposed as a predictor of future knee injury. It mainly involves excess motion in the frontal plane and is known to be greater in individuals with excessive medial knee displacement (MKD). This affects postural control during sports manoeuvres. Previous sports medicine-related research suggests that the nature of these fluctuations provide rich and more sensitive information to identify risk of (re)injury. We aimed to investigate the fluctuations of the centre of pressure (CoP) in individuals with and without excessive MKD. Twenty females (12 controls; 8 excessive MKD) were instructed to perform single-leg landing tasks from three different directions. The participants landed on a force plate and stayed still for 20 seconds. The fluctuations of the anterior-posterior and medial-lateral directions of the CoP were determined through the calculation of Sample Entropy. Mixed-model ANOVAs (3 [Landing Direction] x 2 [Group]) were used. We have found that only the entropy of the medial-lateral direction was different between groups. Individuals with excessive MKD exhibited an increase in entropy values, indicating greater randomness in CoP fluctuations. This suggests a decreased ability to adapt to environmental demands that likely result in an increased risk of injury.

Reliability and validity of a novel Kinect-based software program for measuring a single leg squat

BackgroundThe Single leg squat (SLS) is a movement screening test widely used in clinical settings. The SLS is highly subjective in its nature. Objective measures, such as 3D-motion analyses, are seldom used in daily clinical work. An interactive, Kinect-based 3D-movement analysis system, the Qinematic™, is proposed to be easily used in clinical settings to assess the SLS. The aim of this study was to establish the test-retest reliability and construct validity of Qinematic™ for assessing the SLS. A further aim was to identify angles of medial knee displacement, to summarise the discriminative ability of the SLS measured by Qinematic™.MethodsWe performed a test-retest reliability study (n = 37) of the SLS using Qinematic™ and a construct validity study, in which Qinematic™ data were compared with visual assessment of video-recorded SLS.ResultsThree variables (left knee down, right knee up and down) reached “substantial reliability” (ICC = 0.64–0.69). One variable, “left knee up”, showed a significant difference between the two test occasions (T1–6.34°, T2 0.66°, p = 0.013, ICC = 0.50), and “poor absolute reliability” was seen for all variables (SEM = 9.04–10.66, SDC = 25.06–29.55). A moderate agreement between the visual assessment and Qinematic™ data for various knee angles was shown (Kappa = 0.45–0.58). The best discriminative ability of the SLS was found at a knee angle of 6° (AUC = 0.82, sensitivity = 0.86, specificity = 0.78, PPV = 0.58, NPV = 0.94).ConclusionsQinematic™ shows a poor absolute reliability, and a substantial relative reliability, in measuring a SLS at the way down. This indicates that Qinematic™ should not be recommended for the use on an individual level, but it can possibly be used on a group level. The merged results of the construct validity study indicate that Qinematic™ at 6° of medial displacement can identify subjects with a knee over foot position. In summary, the use of the Qinematic™ net trajectory angle, which estimates the “line of best fit” cannot be recommended to assess a knee medial to foot position and should be reconsidered.

Dynamic knee valgus in competitive alpine skiers: Observation from youth to elite and influence of biological maturation.

Numerous studies investigated the association between dynamic knee valgus and injury risk in post-pubertal and elite athletes; however, normative reference scores for competitive alpine skiers and observations on the development process throughout and beyond athletes' growth spurt are lacking. Thus, the aim of this study was to describe the dynamic knee valgus of competitive alpine skiers during drop jump landings (DJ) and single-leg squats (SLS) with respect to sex, sportive level, and biological maturation. Thirty-seven elite and 104 youth competitive alpine skiers around the growth spurt (U15) were examined for their maximal medial knee displacement (MKD) during DJ and SLS by a marker-based 3D motion analysis evaluating dynamic knee valgus. Additionally, skiers' age, anthropometry and biological maturation were assessed. MKD of youth and elite alpine skiers during DJ was comparable and did not improve with increasing training age. Female U15 skiers (on average further matured) had significantly larger MKD values during DJ than male U15 skiers (less matured) (P<.01). Moreover, MKD during DJ was directly associated with the athlete's individual biological maturation status. MKD values obtained from DJ significantly differed from those obtained during SLS (P<.01). The gender-specific difference in MKD values during DJ and their relationship with maturity offset highlight the fundamental changes to the neuromuscular control system during the growth spurt. Thus, biological maturation needs to be considered as a confounding factor for knee valgus screening. Caution is required when evaluating MKD by using high- and low-dynamic tasks, as corresponding information can differ.

Visual Biofeedback and Changes in Lower Extremity Kinematics in Individuals With Medial Knee Displacement.

Increased frontal-plane knee motion during functional tasks, or medial knee displacement, is a predictor of noncontact anterior cruciate ligament injury and patellofemoral pain. Intervention studies that resulted in a reduced risk of knee injury included some form of feedback to address aberrant lower extremity movement patterns. Research on integrating feedback into single-legged tasks and the ability to train 1 task and test another is limited. To determine if adding real-time visual biofeedback to common lower extremity exercises would improve single-legged landing mechanics in females with medial knee displacement. Cohort study. University laboratory. Twenty-four recreationally active females with medial knee displacement were randomized to a visual-biofeedback group (n = 12; age = 19.75 ± 0.87 years, height = 165.32 ± 8.69 cm, mass = 62.41 ± 8.91 kg) or a control group (n = 12; age = 19.75 ± 0.97 years, height = 166.98 ± 6.89 cm, mass = 59.98 ± 6.24 kg). Individuals in the feedback group viewed a real-time digital model of their body segments generated by Microsoft Kinect. The skeletal model changed color according to the knee-abduction angle of the test limb during the exercise tasks. Participants completed 3 trials of the single-legged drop vertical jump (SL-DVJ) while triplanar kinematics at the trunk, hip, knee, and ankle were collected via 3-dimensional motion capture. The feedback and control groups completed lower extremity exercises with or without real-time visual biofeedback, respectively. After the intervention, participants completed 3 additional trials of the SL-DVJ. At baseline, the feedback group had 3.83° more ankle eversion than the control group after initial contact. After the intervention, the feedback group exhibited 13.03° more knee flexion during the flight phase of the SL-DVJ and 6.16° less knee abduction after initial contact than the control group. The feedback group also demonstrated a 3.02° decrease in peak knee-abduction excursion compared with the baseline values (P = .008). Real-time visual biofeedback immediately improved faulty lower extremity kinematics related to knee-injury risk. Individuals with medial knee displacement adjusted their movement patterns after a single training session and reduced their medial knee motion during a dynamic task.