Knee Loading Research Articles

Altered Knee Loading Following Primary ACL Repair versus ACL Reconstruction.

ACL repair (ACL-r) has recently gained renewed clinical interest for treatment of ACL tears. ACL-r has several potential benefits over ACL reconstruction (ACL-R) including maintaining the native ACL innervation and blood supply, no graft site morbidity, and possible improved knee biomechanics and decrease in osteoarthritis. The purpose of this study was to assess for differences in metrics of knee joint loading during a single limb squat task between individuals following a primary ACL-r versus those who underwent a standard ACL-R with a patella bone-tendon-bone autograft. Case Control Study. The ACL-r group [n: 15, age(yrs): 38.8±13.9] sustained a proximal ACL disruption that was amenable to repair, while the ACL-R group [n: 15, age(yrs): 25.60±1.7] underwent primary reconstruction with patella bone-tendon-bone autograft. At 12-weeks post-operation, both groups completed the IKDC questionnaire and biomechanical testing during performance of the single limb squat. Bilateral peak knee extension moment and total knee joint power as a measure of eccentric loading (contraction) during the descent phase of the squat were calculated on the surgical and non-surgical limb and averaged across the middle three of five trials. Participants also completed quadriceps strength testing on both limbs three months after surgery on an isokinetic dynamometer at 60°/sec.LSI (Limb Strength Index) was calculated for all variables. Separate ANCOVAs were performed on each biomechanical variable to examine differences between groups. The ACL-r had a significantly greater peak knee extension moment LSI (ACL-r: 78.46±5.79%; ACL-R: 56.86±5.79%; p=0.019, ηp2=.186) and total knee joint power LSI (ACL-r: 72.47±7.39%; ACL-R: 39.70±7.39%, p=0.006, ηp2=.245) than the ACL-R group. The ACL-r also had a significantly greater quadriceps LSI than the ACL-R group (ACL-r: 66.318±4.61%, ACL-R: 48.03±4.61%, p=0.013, ηp2=.206). Individuals following ACL-r demonstrate increased knee joint loading symmetry during a single leg squat task and greater quadriceps strength symmetry at 12 weeks post-surgery compared to those who underwent ACL-R. 3.

Fatigue-driven compliance increase and collagen unravelling in mechanically tested anterior cruciate ligament

Approximately 300,000 anterior cruciate ligament (ACL) tears occur annually in the United States, half of which lead to the onset of knee osteoarthritis within 10 years of injury. Repetitive loading is known to result in fatigue damage of both ligament and tendon in the form of collagen unravelling, which can lead to structural failure. However, the relationship between tissue’s structural, compositional, and mechanical changes are poorly understood. Herein we show that repetitive submaximal loading of cadaver knees causes an increase in co-localised induction of collagen unravelling and tissue compliance, especially in regions of greater mineralisation at the ACL femoral enthesis. Upon 100 cycles of 4× bodyweight knee loading, the ACL exhibited greater unravelled collagen in highly mineralized regions across varying levels of stiffness domains as compared to unloaded controls. A decrease in the total area of the most rigid domain, and an increase in the total area of the most compliant domain was also found. The results highlight fatigue-driven changes in both protein structure and mechanics in the more mineralized regions of the ACL enthesis, a known site of clinical ACL failure. The results provide a starting point for designing studies to limit ligament overuse injury.

Multi-frame biomechanical and relaxometry analysis during in vivo loading of the human knee by spiral dualMRI and compressed sensing.

Knee cartilage experiences repetitive loading during physical activities, which is altered during the pathogenesis of diseases like osteoarthritis. Analyzing the biomechanics during motion provides a clear understanding of the dynamics of cartilage deformation and may establish essential imaging biomarkers of early-stage disease. However, in vivo biomechanical analysis of cartilage during rapid motion is not well established. We used spiral displacement encoding with stimulated echoes (DENSE) MRI on in vivo human tibiofemoral cartilage during cyclic varus loading (0.5 Hz) and used compressed sensing on the k-space data. The applied compressive load was set for each participant at 0.5 times body weight on the medial condyle. Relaxometry methods were measured on the cartilage before (T1ρ , T2 ) and after (T1ρ ) varus load. Displacement and strain maps showed a gradual shift of displacement and strain in time. Compressive strain was observed in the medial condyle cartilage and shear strain was roughly half of the compressive strain. Male participants had more displacement in the loading direction compared to females, and T1ρ values did not change after cyclic varus load. Compressed sensing reduced the scanning time up to 25% to 40% when comparing the displacement maps and substantially lowered the noise levels. These results demonstrated the ease of which spiral DENSE MRI could be applied to clinical studies because of the shortened imaging time, while quantifying realistic cartilage deformations that occur through daily activities and that could serve as biomarkers of early osteoarthritis.

The association between kinesiophobia and functional limitations in service members with knee pain

BackgroundKnee diagnoses account for more than 50% of lower extremity musculoskeletal conditions in non-deployed US Service members. However, there is limited information regarding kinesiophobia in Service members with non-operative knee diagnoses. HypothesesThe objectives of this study were to determine the prevalence of high levels of kinesiophobia in US military Service members with knee pain across different knee diagnoses, and to determine the relationships between kinesiophobia and lower extremity function and/or specific functional limitations in Service members with knee pain. It was hypothesized Service members with knee pain would exhibit high levels of kinesiophobia across all knee diagnoses examined, and higher levels of both kinesiophobia and pain would be associated with worse self-reported function in this population. It was also hypothesized higher levels of kinesiophobia would be associated with functional activities with high knee loading. DesignRetrospective cohort study. Level of evidenceIV. MethodsSixty-five US Service members presenting to an outpatient physical therapy clinic were included in this study (20 females; age = 30.8 ± 7.7 years; height = 1.74 ± 0.9 m; mass = 80.7 ± 16.2 kg). Inclusion criterion was the presence of knee pain (duration = 50 ± 59 months); exclusion criterion was knee pain as a sequela of knee surgery. Data regarding demographic, pain chronicity, pain by Numeric Rating Scale (NRS), Tampa Scale of Kinesiophobia (TSK), and Lower Extremity Functional Scale (LEFS) were retrospectively obtained from patients’ medical records. A high level of kinesiophobia was defined as a TSK score of greater than 37 points. Patient diagnoses included: osteoarthritis (n = 16); patellofemoral pain syndrome (n = 23); and other non-operative knee diagnoses (n = 26). Commonality analysis was utilized to determine the effects of age, height, mass, NRS, and TSK on LEFS score. Predictor values were interpreted as <1% = negligible, >1% = small; >9% = moderate, >25% = large. Additionally, exploratory item-specific analyses examined the strength of the relationships between kinesiophobia and LEFS item responses. Binary logistic regression determined if difficulty with an individual LEFS item could be predicted from either NRS or TSK score. Statistical significance was set at P < 0.05. ResultsHigh levels of kinesiophobia were identified in 43 individuals (66%). NRS and TSK explained 19.4% and 8.6% of the unique variance in LEFS, and 38.5% and 20.5% of total variance, respectively. Age, height, and mass explained negligible to small proportions of the unique variance in LEFS. TSK and NRS were independent predictors for 13/20 individual LEFS items, with odds ratios ranging from 1.12 to 3.05 (P < 0.05). ConclusionThe majority of US Service members in this study exhibited high levels of kinesiophobia. Kinesiophobia was significantly related to self-reported functional scores and performance on individual functional tasks in Service members with knee pain. Clinical relevanceTreatment strategies addressing both fear of movement and pain reduction in patients with knee pain may help optimize functional outcomes.

No differences in knee joint loading between individuals who had a medial or lateral meniscectomy: An ancillary study

BackgroundArthroscopic partial meniscectomy is a frequently undertaken procedure for traumatic meniscal injuries. The location of knee joint degeneration and long-term prognosis differs between knees who have had a medial or lateral meniscectomy. However, there is no evidence comparing knee loading following a medial or lateral meniscectomy during sporting tasks. This study compared knee loading during walking and running between individuals who either had a medial or lateral meniscectomy. MethodsKnee kinematic and kinetic data were collected during walking and running in individuals three to twelve months post-surgery. Participants were grouped according to the location of surgery (medial, n = 12, and lateral, n = 16). An independent t-test compared knee biomechanics between the groups and Hedge’s g effects sizes were also conducted. ResultsExternal knee adduction and knee flexion moments were similar between groups for walking and running with negligible to small effect sizes (effect size, 0.08–0.30). Kinematic (effect size, 0.03–0.22) and spatiotemporal (effect size, 0.02–0.59) outcomes were also similar between the groups. ConclusionsThe lack of differences in surrogate knee loading variables between medial and lateral meniscectomy groups was unexpected. These findings suggest that combining groups in the short-term period following surgery is applicable. However, the data presented in this study cannot explain the differences in long-term prognosis between medial and lateral meniscectomies.

Higher knee flexion moment during walking is associated with a lower risk of knee pain developing among the elderly after 24 months.

Knee pain is one of the main problems associated with knee osteoarthritis. The peak external knee adduction moment (KAM) in gait is commonly used to estimate medial knee loading, and elevated KAM has been related to a higher risk of developing knee pain in older adults. Although knee flexion moment (KFM) also contributes to medial knee loading, its role in the development of knee pain remains unclear. To investigate the association between knee moments and the incidence of knee pain in 24 months in asymptomatic older adults. Prospective cohort study. University laboratory. Community-dwelling adults aged 60-80 years were recruited. We excluded participants with knee pain/known arthritis, knee injury, knee/hip joint replacement, cognitive impairment, or neurological conditions. Three-dimensional gait analysis was conducted to compute the peak KFM and KAM. Telephone surveys were conducted 12 and 24 months after the baseline assessment. Self-reported knee pain and its intensity and frequency were captured. Logistic regression with generalized estimating equations was used to examine associations between knee moments and the risk of knee pain. Of the 162 eligible participants who completed the baseline assessment (age: 65.8±4.0 years, 61.1% females), 157 and 138 were also assessed for incident knee pain after 12 and 24 months, respectively. Compared with the lowest tertile, the highest tertile of KFM was significantly related to a lower incidence of frequent knee pain (RR=0.25, 95% CI: 0.08-0.85, P=0.027) in 24 months. In addition, a higher KFM was significantly associated with the lower intensity of incident knee pain after 24 months (β=-1.513; 95% CI: -2.879, -0.147; P=0.030). We also observed trends showing that a higher peak KAM was related to higher risks of developing any (RR=2.48, 95% CI: 0.99-6.20, P=0.053) and frequent (RR=3.82, 95% CI: 0.96-15.1, P=0.057) knee pain in 24 months. A higher sagittal knee moment is associated with a lower risk of knee pain developing in 24 months in older adults. Interventions for promoting sagittal knee moment may be considered in preventative training programs for reducing knee pain among older adults.

A novel method to accurately recreate in vivo loads and kinematics in computational models of the knee

Despite availability of in vivo knee loads and kinematics data, conventional load- and displacement-controlled configurations still can’t accurately predict tibiofemoral loads from kinematics or vice versa. We propose a combined load- and displacement-control method for joint-level simulations of the knee to reliably reproduce in vivo contact mechanics. Prediction errors of the new approach were compared to those of conventional purely load- or displacement-controlled models using in vivo implant loads and kinematics for multiple subjects and activities (CAMS-Knee dataset). Our method reproduced both loads and kinematics more closely than conventional models and thus demonstrates clear advantages for investigating tibiofemoral contact or wear.

Finite element analysis of a healthy knee joint at deep squatting for the study of tibiofemoral and patellofemoral contact

BackgroundIn non-western countries, deep squatting is a daily activity, and prolonged deep squatting is common among occupational squatters. Household tasks, taking a bath, socializing, using toilets, and performing religious acts are among the activities frequently carried out while squatting by the Asian population. High knee loading is responsible for a knee injury and osteoarthritis. Finite element analysis is an effective tool to determine stresses on the knee joint. MethodsMagnetic Resonance Imaging (MRI) and Computed Tomographic (CT) images were acquired of one adult without knee injuries. The CT images were acquired at the fully extended knee and one more set of images was acquired with the knee at a deeply flexed knee position. The MRI was acquired with the fully extended knee. 3-Dimensional models of bones were created using CT and soft tissue using MRI with the help of 3D Slicer software. Kinematics and finite element analysis of the knee was performed for standing and deep squatting posture using Ansys Workbench 2022. ResultsHigh peak stresses were observed at deep squatting compared to standing along with the reduction in the contact area. Peak von Mises stresses on femoral cartilage, tibial cartilage, patellar cartilage, and meniscus were increased from 3.3 MPa to 19.9 MPa, 2.9 MPa to 12.4 MPa, 1.5 MPa to 16.7 MPa and 15.8 MPa to 32.8 MPa respectively during deep squatting. Posterior translation of 7.01 mm, and 12.58 mm was observed for medial and lateral femoral condyle respectively from full extension to 153° knee flexion. ConclusionsIncreased stresses in the knee joint at deep squat posture may cause cartilage damage. A sustained deep squat posture should be avoided for healthy knee joints. More posterior translations of the medial femoral condyle at higher knee flexion angle warrant further investigation.

Knee Loading With Blood Flow Restriction Can Enhance Recovery After Total Knee Arthroplasty.

Total knee arthroplasty (TKA) is one of the most performed operations in the world, especially in the elderly. Aging has a significant effect on joint cartilage, muscle strength, and muscle mass. Following a TKA, despite the significant reduction of symptoms and the improvement in mobility, muscle strengthand muscle mass recovery remains a significant challenge. Restrictions that arise from the surgical procedure include joint loading, functional activities, and range of motion, along with limitations related to the age of the individual and their previous loading history, these are the significant restrictions, at least in the early stages of rehabilitation. Evidence indicates that blood flow restriction (BFR) training has significant potential to enhance recovery via implementation of low-load or low-intensity exercise. While respecting the indications and contraindications related to BFR application, the optimization of metabolic stress seems to offer a bridging therapy to heavy load while reducing pain and inflammation. Thus, the combination of BFR and low loads may improve muscular recovery (strength and mass), and aerobic training protocols appear to show significant enhancement of multiple cardiopulmonary parameters. Mounting evidence, direct and indirect, indicate that BFR training may have the potential to benefit the pre-operative and post-operative TKA rehabilitation phases and enhance functional recoveryand physical abilities in the elderly.

Volume Loss and Recovery in Bovine Knee Meniscus Loaded in Circumferential Tension.

Load-induced volume change is an important aspect of knee meniscus function because volume loss creates fluid pressure, which minimizes friction and helps support compressive loads. The knee meniscus is unusual amongst cartilaginous tissues in that it is loaded not only in axial compression, but also in circumferential tension between its tibial attachments. Despite the physiologic importance of the knee meniscus' tensile properties, its volumetric strain in tension has never been directly measured, and predictions of volume strain in the scientific literature are inconsistent. In this study, we apply uniaxial tension to bovine knee meniscus and use biplanar imaging to directly observe the resulting three-dimensional volume change and unloaded recovery, revealing that tension causes volumetric contraction. Compression is already known to also cause contraction; therefore, all major physiologic loads compress and pressurize the meniscus, inducing fluid outflow. Although passive unloaded recovery is often described as slow relative to loaded loss, here we show that at physiologic strains the volume recovery rate in the meniscus upon unloading is faster than the rate of volume loss. These measurements of volumetric strain are an important step toward a complete theory of knee meniscus fluid flow and load support.

Biomechanical Effects of Manipulating Preferred Cadence During Treadmill Walking in Patients With ACL Reconstruction.

Abnormal gait is common after anterior cruciate ligament reconstruction (ACLR) which may influence osteoarthritis risk in this population. Yet few gait retraining options currently exist in ACLR rehabilitation. Cueing cadence changes is a simple, low-cost method that can alter walking mechanics in healthy adults, but few studies have tested its effectiveness in an ACLR population. Here, we evaluated the acute effects of altering cadence on knee mechanics in patients 9 to 12 months post ACLR. Cueing larger steps will facilitate larger knee angles and moments, while cueing smaller steps would induce smaller knee angles and moments. Randomized cross-sectional design. Level 3. Twenty-eight patients with unilateral ACLR underwent gait assessments on a treadmill at preferred pace. Preferred walking gait was assessed first to obtain preferred cadence. Participants then completed trials while matching an audible beat set to 90% and 110% of preferred cadence in a randomized order. Three-dimensional sagittal and frontal plane biomechanics were evaluated bilaterally. Compared with preferred cadence, cueing larger steps induced larger peak knee flexion moments (KFMs) and knee extension excursions bilaterally (P < 0.01), whereas cueing smaller steps only reduced knee flexion excursions (P < 0.01). Knee adduction moments remain unchanged across conditions and were similar between limbs (P > 0.05). Peak KFMs and excursions were smaller in the injured compared with uninjured limb (P < 0.01). Frontal plane gait outcomes were unchanged across conditions suggesting acute cadence manipulations result in mainly sagittal plane adaptations. Follow-up studies using a longitudinal cadence biofeedback paradigm may be warranted to elucidate the utility of this gait retraining strategy after ACLR. Cueing changes in walking cadence can target sagittal plane knee loading and joint range of motion in ACLR participants. This strategy may offer high clinical translatability given it requires relatively minimal equipment (ie, free metronome app) outside of a treadmill.

Verification of biomechanical factors of gait related to medial knee loading in patients 6 Months after total knee arthroplasty

BackgroundThe knee adduction moment (KAM) is considered an index for estimating the knee mechanical load, and increased KAM peak and KAM impulse are related to increased medial knee load and progression of knee joint degeneration. We aimed to verify the biomechanical factors of gait related to medial knee loading in patients 6 months after TKA. MethodsThirty-nine women who underwent TKA were enrolled. A three-dimensional gait analysis was performed 6 months postoperatively to generate data on the lower limb joint angle, moment, and power at the backward component (braking phase) and forward component (propulsion phase) peaks of the ground reaction force. Medial knee loading was evaluated using the time-integrated value of KAM during the stance period (KAM impulse). The higher the value of the KAM impulse, the higher the medial knee joint load. The relationships between the KAM impulse and the data for biomechanical factors were evaluated using partial correlation analysis with gait speed as a control factor. ResultsIn the braking phase, the KAM impulse positively correlated with the knee adduction angle (r = 0.377) and negatively correlated with the toe-out angle (r = −0.355). The KAM impulse positively correlated with the knee adduction angle (r = 0.402), the hip flexion moment (r = 0.335), and the hip adduction moment (r = 0.565) and negatively correlated with the toe-out angle (r = −0.357) in the propulsive phase. ConclusionThe KAM impulse 6 months after TKA was related to the knee adduction angle, hip flexion moment, hip adduction moment, and toe-out angle. These findings may provide fundamental data for controlling variable medial knee joint load after TKA and implementing patient management strategies to ensure implant durability.

Effects of footwear modification along with physiotherapy on activity of daily living (ADLS) in patients with medial knee osteoarthritis

Background: the management of osteoarthritis (OA) of the knee with biomechanical therapies claimed that application of orthotic devices is another crucial component of a rehabilitation program. Several footwear modifications are used to lessen medial knee loading (MKL), which helps to reduce pain and other symptoms. Objective: to compare the effects of lateral heel wedge insole alone and in combination with medial arch support on ADLs in patient with medial knee OA. Methodology: A randomized clinical trial was conducted on n=60 patients with medial knee OA were randomly allocated in to group A, received lateral heel wedge insole (LHWI) along with medial arch support (MAS) and group B only adjusted with LHWI. Nonprobability convenient sampling technique was used to collect the data on the knee injury and osteoarthritis outcomes score (KOOS) was used as outcome measures. The outcome measures were assessed at the baseline, and after 8 and 16 weeks. Results: The results of independent t-test showed that group A which received LHWI along with MAS showed more significant improvement (p&lt;0.05) in pain, ADLs, sports activity on KOOS questionnaire at each level of assessment than group B which only received the LHWI. But KOOS quality of life scores only showed significant improvement after 8 weeks of intervention in group A while after 16th weeks no significant difference (p=0.09) was observed. Conclusion: the lateral wedge insoles with medial arch support combined with conventional physical therapy protocol is more effective to improve activities of daily living (ADLS) in patients having medial knee osteoarthritis. Keywords: Footwear, osteoarthritis, lateral heel wedge insoles, KOOS, ADLs.

Can static optimization detect changes in peak medial knee contact forces induced by gait modifications?

Medial knee contact force (MCF) is related to the pathomechanics of medial knee osteoarthritis. However, MCF cannot be directly measured in the native knee, making it difficult for therapeutic gait modifications to target this metric. Static optimization, a musculoskeletal simulation technique, can estimate MCF, but there has been little work validating its ability to detect changes in MCF induced by gait modifications. In this study, we quantified the error in MCF estimates from static optimization compared to measurements from instrumented knee replacements during normal walking and seven different gait modifications. We then identified minimum magnitudes of simulated MCF changes for which static optimization correctly identified the direction of change (i.e., whether MCF increased or decreased) at least 70% of the time. A full-body musculoskeletal model with a multi-compartment knee and static optimization was used to estimate MCF. Simulations were evaluated using experimental data from three subjects with instrumented knee replacements who walked with various gait modifications for a total of 115 steps. Static optimization underpredicted the first peak (mean absolute error = 0.16 bodyweights) and overpredicted the second peak (mean absolute error = 0.31 bodyweights) of MCF. Average root mean square error in MCF over stance phase was 0.32 bodyweights. Static optimization detected the direction of change with at least 70% accuracy for early-stance reductions, late-stance reductions, and early-stance increases in peak MCF of at least 0.10 bodyweights. These results suggest that a static optimization approach accurately detects the direction of change in early-stance medial knee loading, potentially making it a valuable tool for evaluating the biomechanical efficacy of gait modifications for knee osteoarthritis.

Change in Descriptive Kinematic Parameters of Patients with Patellofemoral Instability When Compared to Individuals with Healthy Knees—A 3D MRI In Vivo Analysis

Patellofemoral instability (PFI) leads to chronic knee pain, reduced performance and chondromalacia patellae with consecutive osteoarthritis. Therefore, determining the exact patellofemoral contact mechanism, as well as the factors leading to PFI, is of great importance. The present study compares in vivo patellofemoral kinematic parameters and the contact mechanism of volunteers with healthy knees and patients with low flexion patellofemoral instability (PFI). The study was performed with a high-resolution dynamic MRI. In a prospective cohort study, the patellar shift, patella rotation and the patellofemoral cartilage contact areas (CCA) of 17 patients with low flexion PFI were analyzed and compared with 17 healthy volunteers, matched via the TEA distance and sex, in unloaded and loaded conditions. MRI scans were carried out for 0°, 15° and 30° knee flexion in a custom-designed knee loading device. To suppress motion artifacts, motion correction was performed using a moiré phase tracking system with a tracking marker attached to the patella. The patellofemoral kinematic parameters and the CCA was calculated on the basis of semi-automated cartilage and bone segmentation and registrations. Patients with low flexion PFI showed a significant reduction in patellofemoral CCA for 0° (unloaded: p = 0.002, loaded: p = 0.004), 15° (unloaded: p = 0.014, loaded: p = 0.001) and 30° (unloaded: p = 0.008; loaded: p = 0.001) flexion compared to healthy subjects. Additionally, patients with PFI revealed a significantly increased patellar shift when compared to volunteers with healthy knees at 0° (unloaded: p = 0.033; loaded: p = 0.031), 15° (unloaded: p = 0.025; loaded: p = 0.014) and 30° flexion (unloaded: p = 0.030; loaded: p = 0.034) There were no significant differences for patella rotation between patients with PFI and the volunteers, except when, under load at 0° flexion, PFI patients showed increased patellar rotation (p = 0.005. The influence of quadriceps activation on the patellofemoral CCA is reduced in patients with low flexion PFI. Patients with PFI showed different patellofemoral kinematics at low flexion angles in both unloaded and loaded conditions compared to volunteers with healthy knees. Increased patellar shifts and decreased patellofemoral CCAs were observed in low flexion angles. The influence of the quadriceps muscle is diminished in patients with low flexion PFI. Therefore, the goal of patellofemoral stabilizing therapy should be to restore a physiologic contact mechanism and improve patellofemoral congruity for low flexion angles.

Individuals with knee osteoarthritis demonstrate increased passive stiffness of the hip flexor muscles

BackgroundPeople with knee osteoarthritis stand and walk with increased trunk flexion. This altered postural alignment increases hamstring activation, elevating mechanical knee loads during walking. Increased hip flexor stiffness may lead to increased trunk flexion. Therefore, this study compared hip flexor stiffness between healthy individuals and individuals with knee osteoarthritis. This study also sought to understand the biomechanical effect of a simple instruction to reduce trunk flexion by 5° during walking. MethodsTwenty individuals with confirmed knee osteoarthritis and 20 healthy individuals participated. The Thomas test was used to quantity passive stiffness of the hip flexor muscles and three-dimensional motion analysis used to quantify trunk flexion during normal walking. Using a controlled biofeedback protocol, each participant was then instructed to decrease trunk flexion by 5°. ResultsPassive stiffness was greater in the group with knee osteoarthritis (effect size = 1.04). For both groups, there was relatively strong correlation between passive stiffness and trunk flexion in walking (r = 0.61–0.72). The instruction to decrease trunk flexion produced only small, non-significant, reductions in hamstring activation during early stance. ConclusionsThis is the first study to demonstrate that individuals with knee osteoarthritis exhibit increased passive stiffness of the hip muscles. This increased stiffness appears to be linked to increased trunk flexion and may therefore underlie the increased hamstring activation which is associated with this disease. As simple postural instruction does not appear to reduce hamstring activity, interventions may be required which can improve postural alignment by reducing passive stiffness of the hip muscles.

Effect of sprinting velocity on anterior cruciate ligament and knee load during sidestep cutting.

The purpose of the study was to investigate the effect of an increase in sprinting velocity on the anterior cruciate ligament (ACL) load, knee joint load, and activation of femoral muscles using the musculoskeletal modeling approach. Fourteen high school male athletes were recruited (age: 17.4 ± 0.7years, height: 1.75 ± 0.04m, weight: 73.3 ± 8.94kg), with the right foot dominant and physical activity level of about 3-4h per day. The kinematics, kinetics, and co-contraction index (CCI) of the extensors and flexors of the right leg's femoral muscles were calculated. The anterior cruciate ligament load was estimated using the musculoskeletal modeling method. In the results, it was observed that the anterior cruciate ligament load (p < 0.017) increased as sidestep cutting velocity increased, resulting in increased adduction (p < 0.017) and the internal rotation moment of the knee joint. This was significantly higher than when sprinting at a similar velocity. The co-contraction index result, which represents the balanced activation of the femoral extensor and flexor muscles, showed a tendency of decrement with increasing sprinting velocity during sidestep cutting (p < 0.017), whereas no significant differences were observed when running at different sprinting conditions. Therefore, we postulate that factors such as knee joint shear force, extended landing posture with increasing sprinting velocity, internal rotation moment, and femoral muscle activity imbalance influence the increase of anterior cruciate ligament load during a sidestep cutting maneuver.

A Preliminary Investigation into the Neural Correlates of Knee Loading during a Change of Direction Task in Individuals after Anterior Cruciate Ligament Reconstruction.

Central nervous system (CNS) function after ACLR, quantified by the blood oxygen level dependent (BOLD) response, is altered in regions of sensory function during knee movement after ACLR. However, it is unknown how this altered neural response may manifest in knee loading and response to sensory perturbations during sport specific movements. To investigate the relationship among CNS function and lower extremity kinetics, under multiple visual conditions, during 180° change of direction task in individuals with a history of ACLR. Eight participants, 39.3 ± 37.1 months after primary, left ACLR performed repetitive active knee flexion and extension of their involved knee during fMRI scanning. Participants separately performed 3D motion capture analysis of a 180° change of direction task under full vision (FV) and stroboscopic vision (SV) conditions. A neural correlate analysis was performed to associate BOLD signal to knee loading of the left lower extremity. Involved limb peak internal knee extension moment (pKEM) was significantly lower in the SV condition (1.89 ± 0.37 N*m/Kg) compared to the FV condition (2.0 ± 0.34 N*m/Kg) (p = .018). Involved limb pKEM during the SV condition was positively correlated with BOLD signal in the contralateral precuneus and superior parietal lobe (Voxels: 53; p = .017; z-stat max: 6.47; MNI peak: 6, -50, 66). There is a positive association between involved limb pKEM in the SV condition and BOLD response in areas of visual-sensory integration. Activation of contralateral precuneus and superior parietal lobe brain regions may be a strategy to maintain joint loading when vision is perturbed. Level 3.

Sex-Specific associations between hip muscle strength and foot progression angle.

The foot progression angle (FPA) influences knee loading during gait, but its determinants are unclear. The purpose of this study was to compare FPA between males and females and also examine the association between lower extremity kinematics during gait, hip strength, and the FPA. 25 males and 25 females completed 5 gait trials while FPA and frontal and transverse plane hip and knee angles were calculated from the dominant limb during the foot flat portion of stance. Hip extensor/flexor, abductor/adductor, and internal/external rotator strength were evaluated using maximum voluntary isometric contractions. One-way MANOVAs compared gait and strength outcomes. Stepwise regression assessed the association between FPA, and MVIC and kinematics after accounting for speed in males and females. There was no difference in FPA between sexes (p>0.05), but females had greater frontal and transverse plane hip angles compared with males (all p<0.05). Greater hip abduction (p=0.02) strength was associated with greater FPA, but only in males. In males, greater hip abductor strength may contribute to a more neutral position of the foot during gait, which could help maintain an equal knee loading distribution. Our results suggest that there are sex specific control strategies to achieve a similar FPA during gait.

My Top Five Concepts for Selecting Lower Extremity Exercises For Cruciate Ligament and Patellofemoral Rehabilitation.

This clinical commentary will address five key concepts that can be used by clinicians as criteria for selecting lower extremity weight bearing exercises (WBE) and non-weight bearing exercises (NWBE) employed for cruciate ligament and patellofemoral rehabilitation. The following will be discussed for both cruciate ligament and patellofemoral rehabilitation: 1) Knee loading varies between WBE and NWBE; 2) Knee loading varies with technique variations within WBE and NWBE; 3) Knee loading varies between different WBE; 4) Knee loading varies as a function of knee angle; and 5) Knee loading increases with increased knee anterior translation beyond toes.