Neuromuscular characteristics of individuals displaying excessive medial knee displacement

Feasibility Study of Experimental Protocol for the Time-Dependent Mechanical Response of Synthetic Tibia

In this research, an experimental biomechanics construct was developed to reveal the mechanics of distal tibial fracture by submitting synthetic tibiae to cyclic loading, resulting in a combined stress state due to axial compression and bending loads. The synthetic tibia was fixed at the knee but allowed to rotate in the coronal and sagittal planes at the ankle. The first three loading regimes lasted for 4000 cycles/each, and the final until ultimate failure. After 12k±80 cycles, the observed failure patterns closely resembled distal tibial fractures. The collected data during cyclic loading were fitted into a phenomenological model to deduce the time-dependent response of the synthetic tibiae. Images were also collected and analyzed using digital image correlation to deduce the full-field state of strain. The latter revealed that longitudinal strain contours extended in the proximal-distal direction. The transverse strain contours exemplified a medial-to-lateral distribution, attributed to the combined contributions of the Poisson's effect and the flexural deformation from axial and bending components of the applied load, respectively. The experimental construct, full-field characterization, and data analysis approaches can be extended to elucidate the effect of different fixation devices on the overall mechanical behavior of the bone and validate computational models in future research.

Whole-body kinematics of squats two decades following anterior cruciate ligament injury

BACKGROUND

Kinematic studies suggest that injury of the anterior cruciate ligament (ACL) leads to long-lasting movement deficits or compensations to unload the injured knee. This study evaluated lower body kinematics during squats in individuals who suffered unilateral ACL-injury more than 20 years ago.

METHOD

Using motion capture, we compared maximum squat depth, time to complete the squat task, detailed kinematics, estimated kinetic-chain joint moments 0- 80° knee flexion, and weight distribution between legs across three groups with (ACLR, n = 27) and without ACL-reconstructive surgery (ACLPT, physiotherapy only, n = 28), and age-matched non-injured asymptomatic Controls (n = 31, average age across groups 47 years).

RESULTS

ACLPT demonstrated significantly reduced squat depth compared to Controls (p = 0.004), whereas ACLR performed similarly to Controls (p = 1.000). Other outcome variables were comparable between groups. All participants nevertheless demonstrated asymmetric weight distribution between legs but without systematic unloading of the injured side in the ACLgroups.

CONCLUSION

Expected compensatory strategies were not found in the ACL-groups, while poorer squat performance in the ACL-deficient group may depend on pure knee-joint mechanics, or lifestyle factors attributed to a less stable knee decades after ACL-injury.

The Use of Elastic Resistance Bands to Reduce Dynamic Knee Valgus in Squat-Based Movements: A Narrative Review

An elastic band wrapped around the distal thighs has recently been proposed as a method for reducing dynamic knee valgus (medial movement of the knee joint in the frontal/coronal plane) while performing squats. The rationale behind this technique is that, by using an external force to pull the knees into further knee valgus, the band both exaggerates the pre-existing movement and provides additional local proprioceptive input, cueing individuals to adjust their knee alignment. If these mechanisms are true, then elastic bands might indeed reduce dynamic knee valgus, which could be promising for use in injury prevention as excessive knee valgus may be associated with a greater risk of sustaining an ACL rupture and/or other knee injuries. Due to this possibility, certain athletic populations have already adopted the use of elastic bands for training and/or rehab, despite a limited number of studies showing beneficial findings. The purpose of this narrative review is to examine current literature that has assessed lower limb muscle activity and/or lower limb kinematics performance on squat-based movements with or without an elastic band(s). Importantly, this paper will also discuss the key limitations that exist in this area, propose suggestions for future research directions, and provide recommendations for training implementations.

Level of Evidence

5.

The Limitations of Anterior Knee Displacement during Different Barbell Squat Techniques: A Comprehensive Review

Based on seminal research from the 1970s and 1980s, the myth that the knees should only move as far anterior during the barbell squat until they vertically align with the tips of the feet in the sagittal plane still exists today. However, the role of both the hip joint and the lumbar spine, which are exposed to high peak torques during this deliberate restriction in range of motion, has remained largely unnoticed in the traditional literature. More recent anthropometric and biomechanical studies have found disparate results regarding anterior knee displacement during barbell squatting. For a large number of athletes, it may be favorable or even necessary to allow a certain degree of anterior knee displacement in order to achieve optimal training outcomes and minimize the biomechanical stress imparted on the lumbar spine and hip. Overall, restricting this natural movement is likely not an effective strategy for healthy trained individuals. With the exception of knee rehabilitation patients, the contemporary literature suggests it should not be practiced on a general basis.

Relationship between the knee valgus moment and the hip abductor and adductor activity during single-leg landing

OBJECTIVES

To reveal the relationship between the knee valgus moment (KVM) and the hip abductor and adductor activity during single-leg landing.

DESIGN

A cross-sectional study.

SETTING

Laboratory-based, between April 2020 and May 2021.

PARTICIPANTS

Thirty female collegiate athletes.

MAIN OUTCOME MEASURES

KVM, hip adduction angle, hip internal rotation angle, knee valgus angle (KVA), gluteus medius muscle activity, adductor longus muscle activity, adductor longus to gluteus medius activity ratio (ADD/GMED), and vertical component of the ground reaction force (vGRF).

RESULTS

Stepwise multiple regression analysis was performed. KVM was significantly positively associated with KVA (β = 0.613, p < 0.001), vGRF (β = 0.367, p = 0.010), and ADD/GMED (β = 0.289, p = 0.038).

CONCLUSIONS

Increased KVA, vGRF, and ADD/GMED were the independent factors that contributed to increased KVM during single-leg landing, and only ADD/GMED was found among the muscle activity values. The relative muscle activity of the gluteus medius and adductor longus, rather than those of the gluteus medius or adductor longus alone, may be useful in preventing anterior cruciate ligament injury during single-leg landing.

Are proximal and distal neuromuscular parameters able to predict hip and knee frontal plane kinematics during single-leg landing?

OBJECTIVE

To determine if proximal and distal neuromuscular parameters (EMG amplitude and median frequency - MDF) can predict frontal plane kinematics during single-leg landing.

STUDY DESIGN

Cross sectional study.

SETTING

Laboratory.

PARTICIPANTS

Fifteen participants (7 female) performed six single-leg landings with measures of frontal plane kinematics and EMG obtained 230 ms after first foot contact, totalizing 90 landings.

MAIN OUTCOME MEASURES

(i) 2D hip adduction [hip ADD] and knee frontal plane projection angle [knee FPPA]; (ii) EMG amplitude and MDF of gluteus medius [GMed], tensor fascia latae [TFL], peroneus longus [PL] and tibialis anterior [TA].

RESULTS

We observed that MDF of TA was a significant predictor of hip ADD (p = 0.037; β = -0.049 Hz; R²c = 0.30). Also, MDF of PL was significant predictor of knee FPPA (p = 0.043; β = 0.042 Hz; R²c = 0.37). Hip muscles and EMG amplitude parameters were not considered predictors of frontal plane kinematics.

CONCLUSION

The firing frequency of ankle muscles predicted the variance of hip and knee frontal plane kinematics during single-leg landing.

The effectiveness of the comprehensive corrective exercise program on kinematics and strength of lower extremities in males with dynamic knee valgus: a parallel-group randomized wait-list controlled trial

Background

Dynamic knee valgus (DKV) is a prevalent movement impairment widely regarded as a risk factor for lower extremity disorders such as patellofemoral pain syndrome. The present study aimed to investigate the effectiveness of the comprehensive corrective exercise program (CCEP) on kinematics and strength of lower extremities in males with DKV.

Methods

Thirty asymptomatic young men with DKV between the ages of 18 and 28 years participated in this study. They were randomly assigned to the intervention (n = 15) and control groups (n = 15). The intervention group performed the CCEP for three sessions per week for eight weeks, while the control group only did activities of daily living. Hip external rotator and abductor muscle strength and three-dimensional lower extremity kinematics consisting of knee varus/valgus, femur adduction/abduction, femur medial/lateral rotation, and tibial medial/lateral rotation were measured at the baseline and post-test. The data were analyzed using the analysis of covariance (ANCOVA).

Results

There were significant improvements in all kinematics variables in the intervention group after the 8-week CCEP. Moreover, the strength of abductor and external rotator muscle improved in the intervention group (P < 0.05).

Conclusions

The CCEP led to substantial improvements in the selected variables of lower extremity kinematics and muscle strength in participants with DKV during a single-leg squat. These results imply that practitioners should adopt a comprehensive approach to pay simultaneous attention to both proximal and distal segments for improving DKV.

Trial registration

The protocol has been approved in the Registry of Clinical Trials (Registration N: IRCT20180821040843N1) on 2018-12-30.

Females with knee osteoarthritis use a detrimental knee loading strategy when squatting

BACKGROUND

The purpose of this study was to identify sex differences in lower limb kinematics, kinetics, and muscle activation patterns between individuals with osteoarthritis and healthy controls during a two-legged squat.

METHOD

Thirty OA (15 females) and 30 healthy (15 females) participants performed three 2-legged squats. Sagittal and frontal plane hip, knee, and ankle kinematics and kinetics were calculated. Two-way ANOVAs (Sex X OA Status) were used to characterize differences in squatting strategies between sexes and between those with and without knee OA.

RESULTS

A greater decrease in sagittal hip, knee, and ankle range of motion and knee joint power was observed in the OA participants compared to the healthy controls. Females with OA had significantly reduced hip and knee adduction angles compared to the healthy females and males with OA. Females also had decreased hip power, hip flexion, and hip adduction moments and knee adduction moments compared to their male counterparts, with the greatest deficits observed in the females with OA. Females with OA also had the highest magnitude of muscle activation for the quadriceps, hamstrings, and gastrocnemius throughout the squat, while males with OA showed increased activation of the vastus lateralis and medial gastrocnemius compared to the healthy males.

CONCLUSIONS

OA significantly altered biomechanics and neuromuscular control during the squat, with males employing a hip-dominant strategy, allowing them to achieve a greater lower limb range of motion.

The influence of gluteal muscle strength deficits on dynamic knee valgus: a scoping review

Anterior cruciate ligament (ACL) injuries are caused by both contact and non-contact injuries. However, it can be claimed that non-contact ones account approximately for 70% of all cases. Thus, several authors have emphasized the role of reduction of muscle strength as a modifiable risk factor referred to non-contact ACL injury, with the latter being targeted by specific training interventions.The present paper wants to review the available literature specifically on the relationship between dynamic knee valgus, gluteal muscles (GM) strength, apart from the potential correlation regarding ACL injury.After a research based on MEDLINE via PubMed, Google scholar, and Web of Science, a total of 29 articles were collected and thus included.Additionally, this review highlights the crucial role of gluteal muscles in maintaining a correct knee position in the coronal plane during different exercises, namely walking, running, jumping and landing.

Female athletes with ligament dominance exhibiting altered hip and ankle muscle co-contraction patterns compared to healthy individuals during single-leg landing

BACKGROUND

Anterior cruciate ligament (ACL) injury is one of the most serious knee injuries and occurs frequently during exercise. Altered hip and ankle muscle co-contraction patterns may contribute to dynamic knee valgus and ACL injury mechanisms. Lack of dynamic control of ground reaction force (GRF) is known to be contributing factor for ACL injury by placing excessive force on passive structures. Muscle co-contraction is a dynamic mechanism for GRF absorption. Therefore, any alterations in co-contraction might be a risk factor for ACL injury. Ligament dominance is a term to define individuals who rely more on ACL ligament for GRF control.

RESEARCH QUESTION

This study aimed to compare the muscle co-contraction patterns of distal and proximal knee muscles during single leg landing in female athletes with and without ligament dominance.

METHODS

This is a cross-sectional study. A total of 54 female athletes were assigned to the healthy (n = 27) and ligament dominance (n = 27) group based on their Tuck Jump test scores. The electromyography activity of the gluteus medius, adductor longus, tibialis anterior, peroneus longus, medial and lateral gastrocnemius was measured by an electromyography in drop down a 30-cm-high stair. A Multivariate Analysis of Variance (MANOVA) was used for statistical analysis (p ≤ 0.05).

RESULTS

The two groups demonstrated an overall significantly different muscle co-contraction patterns (P < 0.05). There was a decreased in co-contraction of proximal group and an increased co-contraction in the distal muscles in ligament dominant group.

SIGNIFICANCE

The findings have provided evidence to support the notion of neuromuscular imbalances in ligament dominance deficit. These findings can be useful for the coaches and experts to design preventive exercises and modify the current programs for the people affected by ligament dominance.

Hip and ankle strength and range of motion in female soccer players with dynamic knee valgus

BACKGROUND: Dynamic knee valgus (DKV) is a known risk factor for acute and chronic knee injuries and is more frequently diagnosed in females. A real-time single-leg squat test (SLST) could screen for DKV to prevent injuries. OBJECTIVE: To compare the differences in lower extremity strength and range of motion (ROM) in female soccer athletes with and without DKV during an SLST. METHODS: Eighteen subjects with DKV (DKV group) and 18 subjects without DKV (control group) during a single-leg squat were included. Hip strength (flexion, extension, abduction, adduction, internal rotation, and external rotation) was measured with a hand-held dynamometer. Hip ROM (internal and external rotation), and ankle ROM (dorsiflexion with the knee flexed and extended) were measured. Independent t-test was used to compare the averages of the groups. RESULTS: There were significant differences in hip abduction to adduction strength ratio (DKV: 1.48 ± 0.3, control: 1.22 ± 0.26, p< 0.01) and ankle dorsiflexion with knee flexed (DKV: 17.22 ± 6.82, control: 21.22 ± 4.55, p< 0.05) and extended (DKV: 10.14 ± 4.23, control: 14.75 ± 3.40, p< 0.001) between the groups. CONCLUSION: The hip abduction to adduction strength ratio and gastrocnemius and soleus flexibility may be associated factors in dynamic knee valgus and therefore should be assessed and treated, if indicated, as a possible preventive measure in female athletes with this variation.

Preliminary Assessment of Muscle Activity and Muscle Characteristics during Training with Powered Robotic Exoskeleton: A Repeated-Measures Study

A variety of robotic exoskeletons have been developed for patients with spinal cord injuries. However, the optimal training method and period for using a robotic exoskeleton have been uncertain until now. The purpose of this study is to determine the minimum training period for using a robotic exoskeleton with minimal muscle activity by investigating the changes in muscle activity and muscle characteristics of healthy adults during robotic exoskeleton training. A total of 16 people participated in the study. The robotic exoskeleton locomotion training consisted of three 50-min sessions a week for 7 weeks. The assessment consisted of sitting, standing, wide standing, sit-to-stand, and stand-to-sit where muscle activity and muscle characteristics were measured during each motion. All measurements were performed in the first session and every five sessions. Participants showed decreased muscle activity up to 10 sessions of training in the standing position, and 15 sessions in sit-to-stand and stand-to-sit motions. Upper extremity muscles showed decreased muscle activity, tone, stiffness, and logarithmic decrement up to the 15th session. The study results show that at least 15 training sessions are required to use the robotic exoskeleton with minimal load on the musculoskeletal system, and longer training is required for patients with spinal cord injury.

Investigating the landing kinetics factors and preparatory knee muscle activation in female handball players with and without dynamic knee valgus while performing single leg landing

Study aim: to examine the differences in landing kinetics factors (LKF) to assess the whole body stability and preparatory muscle activation (PMA) in female handball players with and without dynamic knee valgus.

Material and methods: Twenty-four professional female handball players (11 with (DKV) and 13 without (Control) dynamic knee valgus) were asked to perform three trials of a single-leg landing. LKF and surface EMG were recorded. Initial contact knee valgus angle (IC KVA), vertical ground reaction force (vGRF), confidence ellipse area of center of pressure (CEA), time to stability (TTS) and EMG from 100 ms prior to ground contact were used in the data analyses.

Results: Multivariate analyzing of LKF showed significant differences between two groups (p = 0.001) while for PMA the result was not significant (p = 0.361).

Conclusion: Altered landing mechanism considered as a predictor of non-contact knee injuries such as ACL rupture. Therefore according to current study it seems important to focus on reducing valgus angle in designing injury prevention program.

Recommendations for Movement Re-training After ACL Reconstruction

It is important to optimise the functional recovery process to enhance patient outcomes after major injury such as anterior cruciate ligament reconstruction (ACLR). Restoring movement quality during sporting-type movements is important prior to return-to-sport (RTS) after ACLR. Alterations in movement quality during an array of functional tasks are common amongst ACLR patients at or near the time of RTS and are associated with worse outcomes after ACLR. The inability to correct movement issues prior to RTS is likely due to the use of incomplete programmes or a lack of volume and intensity of movement re-training programmes. Although most clinicians and researchers understand that re-training movement after ACLR is important (e.g., the 'why'), there is often a disconnect with understanding the 'how' and 'what' of movement re-training post ACLR. The aim of this paper was to discuss factors relevant to movement dysfunction and re-training after ACLR and provide recommendations for clinicians to restore movement quality of patients after ACLR, prior to RTS. The paper recommends: (i) considering the factors which influence the expression of movement quality, which revolve around individual (e.g., neuromuscular, biomechanical, sensorimotor and neurocognitive factors), task-specific and environmental constraints; (ii) incorporating a three-staged movement re-training approach aligned to the ACLR functional recovery process: (1) addressing the neuromuscular and biomechanical and sensorimotor control factors which affect movement quality and motor learning, (2) including a progressive movement re-training approach to re-learn an array of functional tasks optimising coordination and motor learning (3) performing the final aspect of rehabilitation and movement training on the field, in realistic environments progressively simulating the sporting movement demands and environmental constraints; and (iii) effectively designing the movement programme for optimal load management, employing effective coach and feedback techniques and utilising qualitative movement analysis for transition between exercises, stages and for RTS.

The Single Leg Squat Test: A "Top-Down" or "Bottom-Up" Functional Performance Test?

BACKGROUND

Medial knee deviation (MKD) during the single leg squat test (SLST) is a common clinical finding that is often attributed to impairments of proximal muscular structures. Investigations into the relationship between MKD and the foot and ankle complex have provided conflicting results, which may impact clinicians' interpretation of the SLST.

PURPOSE

The purpose of this study was to compare ankle dorsiflexion range of motion (ROM) and foot posture in subjects that perform the SLST with MKD (fail) versus without MKD (pass).

HYPOTHESIS

There will be a difference in ankle dorsiflexion ROM and/or foot posture between healthy individuals that pass and fail the SLST for MKD.

STUDY DESIGN

Cross-sectional study.

METHODS

Sixty-five healthy, active volunteers (sex = 50 female, 15 male; age = 25.2 +/- 5.6 years; height = 1.7 +/- .1 m; weight = 68.5 +/- 13.5 kg) who demonstrated static balance and hip abductor strength sufficient for performance of the SLST participated in the study. Subjects were divided into pass and fail groups based on visual observation of MKD during the SLST. Foot Posture Index (FPI-6) scores and measures of non-weight bearing and weight bearing active ankle dorsiflexion (ROM) were compared.

RESULTS

There were 33 individuals in the pass group and 32 in the fail group. The groups were similar on age (p = .899), sex (p = .341), BMI (p = .818), and Tegner Activity Scale score (p = .456). There were no statistically significant differences between the groups on the FPI-6 (pass group mean = 2.5 +/- 3.9; fail group mean = 2.3 +/- 3.5; p = .599), or any of the measures of dorsiflexion range of motion (non-weight bearing dorsiflexion with knee extended: pass group = 6.9o +/- 3.7o, fail group = 7.8o +/- 3.0o; non-weight bearing dorsiflexion with knee flexed: pass group = 13.5o +/- 5.6o, fail group = 13.9o +/- 5.3o; weight bearing dorsiflexion: pass group = 42.7o +/- 6.0o, 42.7o +/- 8.3o, p = .611).

CONCLUSIONS

Failure on the SLST is not related to differences in clinical measures of active dorsiflexion ROM or foot posture in young, healthy individuals. These findings suggest that clinicians may continue using the SLST to assess neuromuscular performance of the trunk, hip, and knee without ankle dorsiflexion ROM or foot posture contributing to results.

LEVEL OF EVIDENCE

Level 3.

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.

Proximal, Local, and Distal Muscle Morphology in Women With Patellofemoral Pain

Objective:

The objective of this study was to compare proximal, local, and distal muscle morphology in women with and without patellofemoral pain (PFP).

Materials and Methods:

Proximal, local, and distal muscle thicknesses (MTs) were obtained with B-mode sonography in healthy (control group [CG], n = 20) and PFP (PFP group, n = 20) women. In addition, muscle mass was measured by the sum of the synergistic MTs. Data were analyzed by independent t-test, Mann-Whitney U test, and effect size.

Results:

PFP women had smaller gluteus medius ( P = .02, d = 0.7), vastus medialis ( P < .01, d = 1.0), and flexor digitorum brevis ( P < .01, d = 1.0) MT and greater gastrocnemius medialis ( P = .04, d = 0.6) MT than CG. Quadriceps muscle mass ( P = .01, d = 0.8) and foot muscle mass ( P = .008, d = 0.9) were smaller, while plantar flexor muscle mass was greater in the PFP group than in CG ( P = .01, d = 0.8).

Conclusion:

PFP women have proximal, local, and distal MT alterations in comparison with CG, which may explain possible changes in muscle strength and functionality.

Dynamic Knee Valgus in Single-Leg Movement Tasks. Potentially Modifiable Factors and Exercise Training Options. A Literature Review

Dynamic knee valgus (DKV) as an incorrect movement pattern is recognized as a risk factor for lower limb injuries. Therefore, it is important to find the reasons behind this movement to select effective preventive procedures. There is a limited number of publications focusing on specific tasks, separating the double-leg from the single-leg tasks. Test patterns commonly used for DKV assessment, such as single-leg squat (SLS) or single leg landings (SLL), may show different results. The current review presents the modifiable factors of knee valgus in squat and landing single-leg tests in healthy people, as well as exercise training options. The authors used the available literature from PubMed, Scopus, PEDro and clinicaltrials.gov databases, and reviewed physiotherapy journals and books. For the purpose of the review, studies were searched for using 2D or 3D motion analysis methods only in the SLL and SLS tasks among healthy active people. Strengthening and activating gluteal muscles, improving trunk lateral flexion strength, increasing ROM dorsiflexion ankle and midfoot mobility should be taken into account when planning training programs aimed at reducing DKV occurring in SLS. In addition, knee valgus during SLL may occur due to decreased hip abductors, extensors, external rotators strength and higher midfoot mobility. Evidence from several studies supports the addition of biofeedback training exercises to reduce the angles of DKV.

Postural control is altered in females with excessive medial knee displacement

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.

FRAMEWORK FOR OPTIMIZING ACL REHABILITATION UTILIZING A GLOBAL SYSTEMS APPROACH

Knee injuries such as ACL tears commonly occur and there is a high re-injury rate after primary ACL reconstruction with figures estimated at 25%-33%. Clinicians often use hip strengthening as a key component of knee rehabilitation. Evidence suggests that adopting a "regional" or "proximal" approach to rehabilitation can increase hip strength, but motor control often remains unchanged, particularly during more complex tasks such as running and jumping. It has been previously suggested that the current approach to "regional/proximal" rehabilitation is too basic and is constrained by a reductionist philosophy. This clinical commentary provides the clinician a framework for optimizing knee rehabilitation, underpinned by a more global approach. Although this approach remains hip-focused, it can be easily adapted to modify exercise complexity and key loading variables (speed, direction, flight), which will help the clinician to better replicate the sport specific demands on the knee.

LEVEL OF EVIDENCE

5.

The influence of hip rotations on muscle activity during unilateral weight-bearing exercises in individuals with and without genu varum: A cross-sectional study

OBJECTIVES

Hip rotation can influence gluteus medius (Gmed) muscle activity in individuals with genu varum (GV). This study examined different hip rotation positions on muscle activity during unilateral weight-bearing exercises in individuals with and without GV.

DESIGN

Cross-sectional.

SETTING

Outpatient physical therapy center.

PARTICIPANTS

Forty-six physically active males, divided between control (n = 23) and GV groups (n = 23).

MAIN OUTCOME MEASURES

Surface electromyography measured Gmed and tensor fascia latae (TFL) activity during pelvic drop (PD) and wall press (WP) exercises with different hip rotations.

RESULTS

In the control group, WP with external rotation produced greater Gmed/TFL activity compared to other rotation positions. No difference was found for Gmed/TFL with PD in controls. In the GV group, Gmed activity increased with internal rotation in PD and WP; TFL activity increased only with external rotation in WP. Internal hip rotation produced higher Gmed/TFL activity than other positions in the GV group during both exercises. Greater Gmed/TFL activity was observed in the control group than GV during PD with external rotation, and WP with neutral positioning and external rotation.

CONCLUSIONS

WP with external rotation in controls, and PD and WP with internal hip rotation in subjects with GV, are effective exercises to optimize GMed/TFL activity.

Barbell back squat: how do resistance bands affect muscle activation and knee kinematics?

Objectives

This study aimed to determine whether looped resistance bands affect knee kinematics and lower body muscle activation during the barbell back squat.

Methods

Twenty-six healthy participants (13 female, 13 male) calculated their one repetition maximum (RM) prior to data collection. Each participant performed three squats at both 80% and 40% 1RM wearing a light resistance band, an extra-heavy resistance band and no resistance band.

Vicon 3D motion analysis cameras were used to collect the kinematic data, and Delsys Trigno Lab wireless electromyography (EMG) system was used to measure vastus medialis, vastus lateralis, gluteus maximus, gluteus medius and biceps femoris muscle activity. Peak knee flexion angle, peak knee valgus angle and maximum tibial rotation values were examined. Peak EMG values were also analysed after being normalised and expressed as a percentage of maximum voluntary contraction (MVC).

Results

Gluteus maximus (GM) activity is significantly increased when a resistance band is used during squatting. However, squatting with a resistance band is detrimental to knee kinematics as it leads to an increase in knee valgus angle and maximum tibial rotation angle. A direct correlation is recorded between an increase in resistance and an increase in these two angles.

Conclusions

Squatting with resistance bands is likely to increase the risk of knee injury. Coaches and clinicians who already implement this technique are advised to remove resistance band squats from training and rehabilitation programmes. Further research evaluating the long-term effects of using resistance bands during the barbell back squat should be considered.

Lower-Extremity Energy Absorption During Side-Step Maneuvers in Females With Knee Valgus Alignment

CONTEXT

Excessive knee valgus on landing can cause anterior cruciate ligament injury. Therefore, knee valgus alignment may show characteristic energy absorption patterns during landings with lateral movement that impose greater impact forces on the knee joint compared with landings in other alignments.

OBJECTIVE

To investigate the energy absorption strategy in lower-extremities during side steps in females with knee valgus alignment.

DESIGN

Controlled laboratory study.

SETTING

University research laboratory.

PARTICIPANTS

A total of 34 female college students participated in this experiment.

INTERVENTIONS

Participants performed single-leg drop vertical jump and side steps. All participants were divided into valgus (n = 13), neutral (n = 9), and varus (n = 12) groups according to knee position during landing in single-leg drop vertical jumps.

MAIN OUTCOME MEASURES

Lower-extremity joint angles, moments, and negative works were calculated during landing in side steps, and 1-way analysis of variance and post hoc tests were used to determine between-group differences.

RESULTS

Negative works of hip extensors, knee abductors, and ankle plantar flexors during landing in side steps were significantly smaller in the valgus than in the varus group; however, negative work of the knee extensors was significantly greater in the valgus group than in varus group.

CONCLUSIONS

The findings of this study indicated that landing with knee valgus induced the characteristic energy absorption strategy in the lower-extremity. Knee extensors contributed more to energy absorption when landing in knee valgus than in knee varus alignment. Learning to land in knee varus alignment might reduce the impact on the knee joint by increasing the energy absorption capacities of hip extensors, knee abductors, and ankle plantar flexors.

The relationship between single-limb squat and jump-cut kinematics

No objective criteria exist for progressing athletes into cutting manoeuvres following ACL reconstruction (ACLR). The purpose of this study was to evaluate the relationship between a jump-cut task (JC) and the single-limb squat (SLS) in both ACLR and healthy controls. Case-control, laboratory based. Twenty-three participants with a history of ACLR (Age = 21 ± 3 years; Height = 174.5 ± 7.2 cm; Mass = 76.2 ± 9.9 kg) and 23 healthy controls participants (Age = 21 ± 3 years; Height = 173.8 ± 9.2 cm; Mass = 75.0 ± 10.5 kg) were included. Kinematics were collected bilaterally. Correlations between tasks were evaluated for kinematics. Independent sample t-tests were used to evaluate differences between groups for each dependent variable. Peak trunk rotation and medial knee displacement were strongly correlated (p < 0.001, r² = 0.63), between tasks. ACLR group performed SLS and JC tasks with less sagittal plane motion compared to healthy controls (p < 0.05). Lack of frontal and transverse plane control during SLS resulted in positions of increased lateral trunk flexion, hip adduction, and medial knee displacement during JC. The SLS may be considered for use as a clinical predictor of JC during rehabilitation following ACLR.

Hip Abductor and Adductor Muscles Activity Patterns During Landing After Anterior Cruciate Ligament Injury

Context: Hamstring and quadriceps activity adaptations are well known in individuals with anterior cruciate ligament deficiency (ACLD) and reconstructed (ACLR) to potentially compensate for knee joint instability. However, few studies have explored hip muscles activity patterns after ACL injury. Objective: To examine the activation characteristics of gluteus medius (GMED) and adductor longus in ACLR and ACLD subjects compared with controls. Design: Case–control study. Setting: Athletic training room and university lab. Participants: Twelve healthy and 24 ACL-injured (12 ACLR and 12 ACLD) recreationally active male volunteers. Interventions: Surface electromyography of the GMED and adductor longus were recorded during a single-leg vertical drop landing and normalized to maximum voluntary isometric contractions. Main Outcome Measures: Preparatory and reactive muscle activity and coactivation were analyzed from 100 milliseconds prior to initial contact to 250 milliseconds postcontact. Results: During reactive activity, ACL-injured (ACLR and ACLD) participants demonstrated significantly lower peak GMED activity compared with controls (F = 4.33, P = .02). In addition, ACLR participants exhibited significantly lower reactive GMED:adductor longus coactivation muscle activity compared with controls (F = 4.09, P = .03). Conclusion: Our findings suggest neuromuscular adaptations of the hip musculature are present in people at least 2 years from ACL injury. GMED activation exercises should be considered in designing rehabilitation programs for ACL-injured individuals.

Restricted Unilateral Ankle Dorsiflexion Movement Increases Interlimb Vertical Force Asymmetries in Bilateral Bodyweight Squatting

Crowe, MA, Bampouras, TM, Small, K, and Howe, LP. Restricted unilateral ankle dorsiflexion movement increases interlimb vertical force asymmetries in bilateral bodyweight squatting. J Strength Cond Res 34(2): 332-336, 2020-The purpose of this study was to investigate the effect of unilateral restrictions in ankle-dorsiflexion range of motion (DF-ROM) on interlimb vertical ground reaction force (vGRF) asymmetries. Twenty healthy and physically active volunteers (age 23 ± 3 years; height 1.72 ± 0.1 m; mass 74.9 ± 20.3 kg) performed 3 barefoot bodyweight squats (control condition) and with a 10° custom-built forefoot wedge under the right foot to artificially imitate ankle DF-ROM restriction (wedge condition). Force data were used to calculate the mean asymmetry index score for the upper descent phase, lower descent phase, lower ascent phase, and upper ascent phase during the bilateral squat. Significant differences were found for comparisons for each phase between conditions, with effect sizes ranging between 0.7 and 1.1. Asymmetry index scores indicated that for all phases, the unrestricted limb in the wedge condition produced greater vGRF. Therefore, interlimb differences in ankle DF-ROM can cause interlimb asymmetries in vGRF during bilateral squatting. As such, athletes with asymmetrical squat mechanics should be screened for interlimb differences in ankle DF-ROM to ascertain whether it is a contributing factor.

Can Functional Movement Assessment Predict Football Head Impact Biomechanics?

PURPOSE

The purposes of this study was to determine functional movement assessments' ability to predict head impact biomechanics in college football players and to determine whether head impact biomechanics could explain preseason to postseason changes in functional movement performance.

METHODS

Participants (N = 44; mass, 109.0 ± 20.8 kg; age, 20.0 ± 1.3 yr) underwent two preseason and postseason functional movement assessment screenings: 1) Fusionetics Movement Efficiency Test and 2) Landing Error Scoring System (LESS). Fusionetics is scored 0 to 100, and participants were categorized into the following movement quality groups as previously published: good (≥75), moderate (50-75), and poor (<50). The LESS is scored 0 to 17, and participants were categorized into the following previously published movement quality groups: good (≤5 errors), moderate (6-7 errors), and poor (>7 errors). The Head Impact Telemetry (HIT) System measured head impact frequency and magnitude (linear acceleration and rotational acceleration). An encoder with six single-axis accelerometers was inserted between the padding of a commercially available Riddell football helmet. We used random intercepts general linear-mixed models to analyze our data.

RESULTS

There were no effects of preseason movement assessment group on the two Head Impact Telemetry System impact outcomes: linear acceleration and rotational acceleration. Head impact frequency did not significantly predict preseason to postseason score changes obtained from the Fusionetics (F1,36 = 0.22, P = 0.643, R = 0.006) or the LESS (F1,36 < 0.01, P = 0.988, R < 0.001) assessments.

CONCLUSIONS

Previous research has demonstrated an association between concussion and musculoskeletal injury, as well as functional movement assessment performance and musculoskeletal injury. The functional movement assessments chosen may not be sensitive enough to detect neurological and neuromuscular differences within the sample and subtle changes after sustaining head impacts.

Inertial measurement unit-based pose estimation: Analyzing and reducing sensitivity to sensor placement and body measures

Introduction

Inertial measurement units have been proposed for automated pose estimation and exercise monitoring in clinical settings. However, many existing methods assume an extensive calibration procedure, which may not be realizable in clinical practice. In this study, an inertial measurement unit-based pose estimation method using extended Kalman filter and kinematic chain modeling is adapted for lower body pose estimation during clinical mobility tests such as the single leg squat, and the sensitivity to parameter calibration is investigated.

Methods

The sensitivity of pose estimation accuracy to each of the kinematic model and sensor placement parameters was analyzed. Sensitivity analysis results suggested that accurate extraction of inertial measurement unit orientation on the body is a key factor in improving the accuracy. Hence, a simple calibration protocol was proposed to reach a better approximation for inertial measurement unit orientation.

Results

After applying the protocol, the ankle, knee, and hip joint angle errors improved to 4 . 2 ∘ , 6 . 3 ∘ , and 8 . 3 ∘ , without the need for any other calibration.

Conclusions

Only a small subset of kinematic and sensor parameters contribute significantly to pose estimation accuracy when using body worn inertial sensors. A simple calibration procedure identifying the inertial measurement unit orientation on the body can provide good pose estimation performance.

THERABAND® CLX gold reduces knee-width index and range of motion during overhead, barbell squatting

This study examined the influence of the Theraband^TM CLX gold band on lower-limb muscle activity and kinematics during an overhead barbell squat. Participants performed two sets (band and no-band) of 12 repetitions of overhead barbell squats at 25% bodyweight. Three-dimensional kinematics were measured using motion capture with rigid bodies placed bilaterally on the foot, shank, thigh and thorax. Electromyography was collected from seven, bilateral muscles of the lower-limb and was unchanged for all muscles between conditions. Medial knee collapse was calculated using a knee-width index (KWI) ratio of the distance between the lateral epicondyles of the femur and the lateral malleoli. Average KWI was smaller during the band condition for the concentric (No band: 0.99 ± 0.05, Band: 0.97 ± 0.06, p < 0.05) and eccentric phases (No band: 1.00 ± 0.06, Band: 0.97 ± 0.05, p < 0.05). KWI was significantly smaller with the use of the Theraband^TM CLX. As the gold band is the strongest of the CLX offerings, any benefit of increased proprioception may have been lost due to the high resistance of the band. Further research examining the dose-response of elastic band resistance to knee alignment may be needed to inform proper exercise prescription.

Lower-Extremity Muscle Activity, Kinematics, and Dynamic Postural Control in Individuals With Patellofemoral Pain

CONTEXT

Altered lower-extremity muscle activity has been associated with lower-extremity kinematics in individuals with patellofemoral pain (PFP). However, few studies have examined these relationships, and the results are inconsistent.

OBJECTIVE

To compare the lower-extremity muscle activity, kinematics, pain level, and reach distance during the anterior reach of the star excursion balance test (SEBT) between participants with PFP and healthy individuals (control [CON] group).

DESIGN

Case control.

SETTING

Research laboratory.

PARTICIPANTS

Twenty-eight (PFP = 14 and CON = 14) participants volunteered.

INTERVENTION

Each participant performed 3 maximal voluntary isometric contractions of the gluteus maximus, gluteus medius (GMED), adductor longus (AL), and vastus medialis, and 5 anterior reaches of the SEBT.

MAIN OUTCOME MEASURES

Three-dimensional joint kinematics of the hip and knee at the time of touchdown of the SEBT and integrated electromyography of each muscle were recorded during the descent phase of the SEBT. Coactivation ratios between the GMED and AL were calculated (GMED/AL). Pain level was assessed at the baseline and during performance of the SEBT, using a visual analog scale.

RESULTS

Participants with PFP demonstrated decreased GMED/AL coactivation ratio (P = .01) and shorter reach distance (P = .01) during anterior reach of the SEBT compared with the CON group. Participants with PFP demonstrated higher pain levels at baseline (P = .03) and during test performance (P < .001) compared with the CON group and increased pain level during the test performance compared with the baseline (P < .001). No other significant differences were observed.

CONCLUSIONS

There were alterations in muscle activity during SEBT performance, suggesting that overactivity of AL relative to GMED is a unique neural recruitment pattern in those with PFP. However, hip and knee joint kinematics did not seem to contribute to deficits in the anterior reach distance, suggesting a need for continued assessment of these deficiencies.

Modifiable Factors Associated with Knee Abduction During Weight-Bearing Activities: A Systematic Review and Meta-Analysis

BACKGROUND

Increased knee abduction angle during activity is suggested to be a risk factor for sustaining an anterior cruciate ligament (ACL) injury or developing patellofemoral pain syndrome (PFPS). Knowledge of the modifiable mechanisms that are associated with increased knee abduction will aid in the appropriate design of preventive and rehabilitative strategies for these injuries.

OBJECTIVE

Our objective was to systematically review modifiable mechanisms contributing to increased knee abduction in healthy people and in individuals with an ACL injury or PFPS.

METHODS

We performed a systematic review and meta-analysis according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We searched the databases MEDLINE, CINAHL, and Embase until September 2015. Inclusion criteria were studies in healthy individuals and/or those with ACL injury or PFPS reporting (1) muscle strength, muscle activation, proprioception, and/or range of motion (ROM) and (2) knee abduction angle assessed with either motion analysis or visual observation during weight-bearing activity.

RESULTS

In total, 33 articles were included. Reduced trunk strength, reduced gluteus maximus amplitude, decreased ankle ROM, and increased hip external rotation ROM were moderately associated with increased knee abduction angle (r -0.34 or higher, standardized difference in means (SDM) greater than -0.39, p < 0.05, articles n = 3, total sample size n = 101-114) in healthy individuals. Decreased strength of hip abductors, external rotators, and extensors and knee flexors were at most weakly associated with increased knee abduction angle (r ≤ 0.21, p = 0.013-0.426, articles n = 2-9, total sample size n = 80-311). Too few articles included patients with knee injury to be included in any meta-analysis.

CONCLUSION

The associations identified in this review indicate that investigation of strengthening of the trunk muscles, and improvement of gluteus maximus activation and ankle ROM to change knee kinematics is merited. Studies on modifiable factors associated with increased knee abduction angle in people with knee injury are needed.

Automated Assessment of Dynamic Knee Valgus and Risk of Knee Injury During the Single Leg Squat

Many clinical assessment protocols of the lower limb rely on the evaluation of functional movement tests such as the single leg squat (SLS), which are often assessed visually. Visual assessment is subjective and depends on the experience of the clinician. In this paper, an inertial measurement unit (IMU)-based method for automated assessment of squat quality is proposed to provide clinicians with a quantitative measure of SLS performance. A set of three IMUs was used to estimate the joint angles, velocities, and accelerations of the squatting leg. Statistical time domain features were generated from these measurements. The most informative features were used for classifier training. A data set of SLS performed by healthy participants was collected and labeled by three expert clinical raters using two different labeling criteria: "observed amount of knee valgus" and "overall risk of injury". The results showed that both flexion at the hip and knee, as well as hip and ankle internal rotation are discriminative features, and that participants with "poor" squats bend the hip and knee less than those with better squat performance. Furthermore, improved classification performance is achieved for females by training separate classifiers stratified by gender. Classification results showed excellent accuracy, 95.7 % for classifying squat quality as "poor" or "good" and 94.6% for differentiating between high and no risk of injury.

The acute effects of ankle mobilisations on lower extremity joint kinematics

INTRODUCTION

Previous investigations have identified compensatory movement strategies (CMS) within the lower extremity or lumbopelvic complex during closed chain exercises may be associated with a loss of ankle dorsiflexion range of motion (ROM). The aim of this study was to investigate the acute effects of ankle mobilisations on proximal joint kinematics during a movement task that demands a high amount of ankle dorsiflexion ROM.

METHODS

Eight healthy males (mean (SD) age 25 (4) years) demonstrating side-to-side asymmetry during the weight-bearing lunge test (WBLT) and CMS during the single-leg step-down exercise were accepted for this study. Participants completed five repetitions of a single-leg step-down, both before and after an ankle mobilisation intervention aimed at improving joint athrokinematics. A Vicon motion capture system recorded 3D joint and segment kinematics of the ankle, knee, hip and pelvis. A paired samples t-test was used to identify significant changes of lower extremity joint kinematics during the single-leg step-down, before and after mobilisation.

RESULTS

Following the mobilisation intervention, statistically significant gains in ankle dorsiflexion ROM were identified during the WBLT [mean difference 2.425 (0.9377) centimeters, t = -7.315, p < 0.01]. No evidence was found of altered joint kinematics during the single-leg step-down.

CONCLUSION

These findings indicate that increases in ankle dorsiflexion ROM do not automatically integrate into functional movement tasks.

Gait adaptations with aging in healthy participants and people with knee-joint osteoarthritis

The relationship between age and gait characteristics in people with and without medial compartment osteoarthritis (OA) remains unclear. We aimed to characterize this relationship and to relate biomechanical and structural parameters in a subset of OA patients. Twenty five participants with diagnosed unilateral medial knee OA and 84 healthy participants, with no known knee pathology were recruited. 3D motion capture was used to analyse sagittal and coronal plane gait parameters while participants walked at a comfortable speed. Participants were categorized according to age (18-30, 31-59 and 60+ years), and those with and without OA were compared between and within age groups. In a subset of OA patients, clinically available Computed Tomography images were used to assess joint structure. Differences in coronal plane kinematics at the hip and knee were noted in participants with OA particularly those who were older compared with our healthy controls, as well as increased knee moments. Knee adduction moment correlated with structural parameters in the subset of OA patients. Increased knee moments and altered kinematics were observed in older participants presenting with OA only, which seem to be related to morphological changes in the joint due to OA, as opposed to being related to the initial cause of medial knee OA.

The Interrelationship of Common Clinical Movement Screens: Establishing Population-Specific Norms in a Large Cohort of Military Applicants

CONTEXT

 Musculoskeletal injuries (MSK-Is) are a leading cause of missed duty time and morbidity in the military. Modifiable risk factors for MSK-Is, such as inadequate core stability, poor movement patterns, and dynamic balance deficits, have not been identified in military applicants on entering service.

OBJECTIVE

 To establish normative functional movement data using a series of screens in military applicants entering basic training and explore relationships among several movement tests.

DESIGN

 Cross-sectional study.

SETTING

 Military Entrance Processing Station.

PATIENTS OR OTHER PARTICIPANTS

 A total of 1714 (1434 male, 280 female) military applicants entering the US Army (n = 546), Navy (n = 414), Air Force (n = 229), or Marine Corps (n = 525).

INTERVENTION(S)

 We conducted the Functional Movement Screen (FMS), Y-Balance Test (YBT), overhead squat (OHS), and Landing Error Scoring System (LESS). Movements were assessed using the scoring convention for each screen.

MAIN OUTCOME MEASURE(S)

 The FMS, YBT, OHS, and LESS scores and associations among the movement screens as well as clinical meaningfulness.

RESULTS

 A total of 1037 of the 1714 enrolled applicants were screened on the day they left for basic training. Normative means for this population were established: FMS = 14.7 ± 1.8, YBT anterior-reach difference = 3.1 ± 3.0 cm, mean YBT composite differences = 8.0 ± 6.8 cm, mean YBT composite percentage = 90.9% ± 8.3%, OHS errors = 5.0 ± 2.8, and LESS score = 5.7 ± 2.1. Backward regression results revealed that the YBT composite percentage was related to the FMS and OHS scores in males and to the FMS and LESS results in females. However, clinically meaningful relationships between the tests varied for both males and females.

CONCLUSIONS

 Sex-normative values for the FMS, YBT, OHS, and LESS screens were established for US military applicants, and some of the assessments overlapped. Overall, males performed better on the OHS and LESS and achieved a greater YBT composite percentage than females. The regression results revealed movement screen performance relationships that varied by sex and clinical meaningfulness. In future studies, we will determine if performance on any of the screens is associated with MSK-Is in basic trainees.

The influence of knee alignment on lower extremity kinetics during squats

The squat is an assessment of lower extremity alignment during movement, however there is little information regarding altered joint kinetics during poorly performed squats. The purpose of this study was to examine changes in joint kinetics and power from altered knee alignment during a squat. Thirty participants completed squats while displacing the knee medially, anteriorly, and with neutral alignment (control). Sagittal and frontal plane torques at the ankle, knee, and hip were altered in the descending and ascending phase of the squat in both the medial and anterior malaligned squat compared to the control squat. Ankle and trunk power increased and hip power decreased in the medial malaligned squat compared to the control squat. Ankle, knee, and trunk power increased and hip power decreased in the anterior malaligned squat compared to the control squat. Changes in joint torques and power during malaligned squats suggest that altered knee alignment increases ankle and trunk involvement to execute the movement. Increased anterior knee excursion during squatting may also lead to persistent altered loading of the ankle and knee. Sports medicine professionals using the squat for quadriceps strengthening must consider knee alignment to reduce ankle and trunk involvement during the movement.

Classification of squat quality with inertial measurement units in the single leg squat mobility test

Many assessment and diagnosis protocols in rehabilitation, orthopedic surgery and sports medicine rely on mobility tests like the Single Leg Squat (SLS). In this study, a set of three Inertial Measurement Units (IMUs) were used to estimate the joint pose during SLS and to classify the SLS as poor, moderate or good. An Extended Kalman Filter pose estimation method was used to estimate kinematic joint variables, and time domain features were generated based on these variables. The most important features were then selected and used to train Support Vector Machine (SVM), Linear Multinomial Logistic Regression, and Decision Tree classifiers. The results of feature selection highlight the importance of the ankle internal rotation (IR) angle in classifying SLS. Classification results on a human motion dataset achieved an accuracy of 98% for the two-class problem using SVM, while for 3 class classification, the maximum accuracy was 73% using Decision Tree.

Maturation and Sex Differences in Neuromuscular Characteristics of Youth Athletes

Understanding how neuromuscular factors that are associated with lower extremity injury risk, such as landing kinematics, muscle strength, and flexibility, change as children mature may enhance age-specific recommendations for injury prevention programs. The purpose of this study was to compare these factors in prepubertal, pubertal, and postpubertal male and female athletes. Subjects were classified on maturation stage (prepubertal: 16 males, 15 females, age: 9 ± 1 years; pubertal: 13 males, 12 females, age: 12 ± 3 years; postpubertal: 30 males, 27 females, age: 16 ± 2 years). Researchers measured lower extremity isometric muscle strength and flexibility and evaluated kinematics and vertical ground reaction forces (VGRFs) during a jump-landing task. Three-dimensional kinematics at initial contact (IC), joint displacements, and peak VGRF were calculated. Separate multivariate analyses of variance were performed to evaluate sex and maturation differences (α ≤ 0.05). Postpubertal females landed with less knee flexion at IC (p = 0.006) and demonstrated lower knee extension strength (p = 0.01) than prepubertal and pubertal females. Postpubertal males landed with less hip adduction displacement (postpubertal males = 12.53 ± 6.15°, prepubertal males = 18.84 ± 7.47°; p = 0.04) and less peak VGRF (postpubertal males = 1.53 ± 0.27% body weight [BW], prepubertal males = 1.99 ± 0.32% BW; p = 0.03) compared with prepubertal males. These findings suggest encouraging sagittal plane absorption and decreasing frontal plane motion at the hip, whereas maintaining quadriceps strength may be important for reducing injury risk in postpubertal athletes.

The association of dorsiflexion flexibility on knee kinematics and kinetics during a drop vertical jump in healthy female athletes

PURPOSE

While previous studies have examined the association between ankle dorsiflexion flexibility and deleterious landing postures, it is not currently known how landing kinetics are influenced by ankle dorsiflexion flexibility. The purpose of this study was to examine whether ankle dorsiflexion flexibility was associated with landing kinematics and kinetics that have been shown to increase the risk of anterior cruciate ligament (ACL) injury in female athletes.

METHODS

Twenty-three female collegiate soccer players participated in a preseason screening that included the assessment of ankle dorsiflexion flexibility and lower-body kinematics and kinetics during a drop vertical jump task.

RESULTS

The results demonstrated that females with less ankle dorsiflexion flexibility exhibited greater peak knee abduction moments (r = -.442), greater peak knee abduction angles (r = .355), and less peak knee flexion angles (r = .385) during landing. The range of dorsiflexion flexibility for the current study was between 9° and 23° (mean = 15.0°; SD 3.9°).

CONCLUSION

Dorsiflexion flexibility may serve as a useful clinical measure to predict poor landing postures and external forces that have been associated with increased knee injury risk. Rehabilitation specialists can provide interventions aimed at improving dorsiflexion flexibility in order to ameliorate the impact of this modifiable factor on deleterious landing kinematics and kinetics in female athletes.

LEVEL OF EVIDENCE

II.

Altered knee and ankle kinematics during squatting in those with limited weight-bearing-lunge ankle-dorsiflexion range of motion

CONTEXT

Ankle-dorsiflexion (DF) range of motion (ROM) may influence movement variables that are known to affect anterior cruciate ligament loading, such as knee valgus and knee flexion. To our knowledge, researchers have not studied individuals with limited or normal ankle DF-ROM to investigate the relationship between those factors and the lower extremity movement patterns associated with anterior cruciate ligament injury.

OBJECTIVE

To determine, using 2 different measurement techniques, whether knee- and ankle-joint kinematics differ between participants with limited and normal ankle DF-ROM.

DESIGN

Cross-sectional study.

SETTING

Sports medicine research laboratory.

PATIENTS OR OTHER PARTICIPANTS

Forty physically active adults (20 with limited ankle DF-ROM, 20 with normal ankle DF-ROM).

MAIN OUTCOME MEASURE(S)

Ankle DF-ROM was assessed using 2 techniques: (1) nonweight-bearing ankle DF-ROM with the knee straight, and (2) weight-bearing lunge (WBL). Knee flexion, knee valgus-varus, knee internal-external rotation, and ankle DF displacements were assessed during the overhead-squat, single-legged squat, and jump-landing tasks. Separate 1-way analyses of variance were performed to determine whether differences in knee- and ankle-joint kinematics existed between the normal and limited groups for each assessment.

RESULTS

We observed no differences between the normal and limited groups when classifying groups based on nonweight-bearing passive-ankle DF-ROM. However, individuals with greater ankle DF-ROM during the WBL displayed greater knee-flexion and ankle-DF displacement and peak knee flexion during the overhead-squat and single-legged squat tasks. In addition, those individuals also demonstrated greater knee-varus displacement during the single-legged squat.

CONCLUSIONS

Greater ankle DF-ROM assessed during the WBL was associated with greater knee-flexion and ankle-DF displacement during both squatting tasks as well as greater knee-varus displacement during the single-legged squat. Assessment of ankle DF-ROM using the WBL provided important insight into compensatory movement patterns during squatting, whereas nonweight-bearing passive ankle DF-ROM did not. Improving ankle DF-ROM during the WBL may be an important intervention for altering high-risk movement patterns commonly associated with noncontact anterior cruciate ligament injury.

Altered movement patterns and muscular activity during single and double leg squats in individuals with anterior cruciate ligament injury

BACKGROUND

Individuals with Anterior Cruciate Ligament (ACL) injury often show altered movement patterns, suggested to be partly due to impaired sensorimotor control. Here, we therefore aimed to assess muscular activity during movements often used in ACL-rehabilitation and to characterize associations between deviations in muscular activity and specific altered movement patterns, using and further exploring the previously developed Test for substitution Patterns (TSP).

METHODS

Sixteen participants (10 women) with unilateral ACL rupture performed Single and Double Leg Squats (SLS; DLS). Altered movement patterns were scored according to TSP, and Surface Electromyography (SEMG) was recorded bilaterally in six hip, thigh and shank muscles. To quantify deviations in muscular activity, SEMG ratios were calculated between homonymous muscles on injured and non-injured sides, and between antagonistic muscles on the same side. Correlations between deviations of injured/non-injured side SEMG ratios and specific altered movement patterns were calculated.

RESULTS

Injured/non-injured ratios were low at transition from knee flexion to extension in quadriceps in SLS, and in quadriceps and hamstrings in DLS. On injured side, the quadriceps/hamstrings ratio prior to the beginning of DLS and end of DLS and SLS, and tibialis/gastrocnemius ratio at end of DLS were lower than on non-injured side. Correlations were found between specific altered movement patterns and deviating muscular activity at transition from knee flexion to extension in SLS, indicating that the more deviating the muscular activity on injured side, the more pronounced the altered movement pattern. "Knee medial to supporting foot" correlated to lower injured/non-injured ratios in gluteus medius (rs = -0.73, p = 0.001), "lateral displacement of hip-pelvis-region" to lower injured/non-injured ratios in quadriceps (rs = -0.54, p = 0.03) and "displacement of trunk" to higher injured/non-injured ratios in gluteus medius (rs = 0.62, p = 0.01).

CONCLUSIONS

Deviations in muscular activity between injured and non-injured sides and between antagonistic muscular activity within injured as compared to non-injured sides indicated specific alterations in sensorimotor control of the lower limb in individuals with ACL rupture. Also, correlations between deviating muscular activity and specific altered movement patterns were suggested as indications of altered sensorimotor control. We therefore advocate that quantitative assessments of altered movement patterns should be considered in ACL-rehabilitation.

Range of motion, postural alignment, and LESS score differences of those with and without excessive medial knee displacement

OBJECTIVE

To determine range of motion (ROM), postural alignment, and dynamic motion differences between those with and without medial knee displacement (MKD) during the overhead squat (OHS). We hypothesized those with MKD would have restricted ROM, differing postural alignment, and poorer quality dynamic motion than those without MKD.

DESIGN

Observational.

SETTING

University Research Laboratory.

PARTICIPANTS

Ninety-seven healthy recreationally active college-aged individuals.

INDEPENDENT VARIABLES

Groups were determined by the presence (MKD group) or absence (control group) of MKD during an OHS.

MAIN OUTCOME MEASURES

Range of motion measures were active and passive ankle dorsiflexion with the knee straight and bent, hip internal and external rotation, and hip abduction. Postural alignment measures were Q angle, navicular drop, and genu recurvatum. Quality of dynamic motion was measured using total Landing Error Scoring System (LESS) score.

RESULTS

The MKD group had significantly less active (P = 0.017) and passive (P = 0.045) ankle dorsiflexion with the knee straight, as well as significantly increased Q angle (P = 0.004) and decreased navicular drop (P = 0.009). There were no significant differences in total LESS score or the other outcome measures.

CONCLUSIONS

There is select ROM, such as ankle dorsiflexion, and postural measures clinicians can screen for that may be related to increased MKD and theoretically elevated risk of injury.

Kinematic Differences Between Those With and Without Medial Knee Displacement During a Single-leg Squat

A greater knee valgus angle is a risk factor for lower extremity injuries. Visually observed medial knee displacement is used as a proxy for knee valgus motion during movement assessments in an attempt to identify individuals at heightened risk for injury. The validity of medial knee displacement as an indicator of valgus motion has yet to be determined during a single-leg squat. This study compared three-dimensional knee and hip angles between participants who displayed medial knee displacement (MKD group) during a single-leg squat and those who did not (control group). Participants completed five single-leg squats. An electromagnetic motion tracking system was used to quantify peak knee and hip joint angles during the descent phase of each squat. MANOVA identified a difference between the MKD and control group kinematics. ANOVA post hoc testing revealed greater knee valgus angle in the MKD (12.86 ± 5.76) compared with the control (6.08 ± 5.23) group. There were no other differences between groups. Medial knee displacement is indicative of knee valgus motion; however, it is not indicative of greater knee or hip rotation, or hip adduction. These data indicate that clinicians can accurately identify individuals with greater knee valgus angle through visually observed medial knee displacement.