Adduction Moment Research Articles

NO KNEE OVERLOADING IN RATS WITH DESTABILIZATION OF THE MEDIAL MENISCUS: A STUDY BASED ON INTEGRATED MOTION CAPTURE DATA AND HIGH-THROUGHPUT MUSCULOSKELETAL WORKFLOW

Altered mechanical loading is a widely suggested, but poorly understood potential cause of cartilage degeneration in osteoarthritis. In rodents, osteoarthritis is induced following destabilization of the medial meniscus (DMM). This study estimates knee kinematics and contact forces in rats with DMM to gain better insight into the specific mechanisms underlying disease development in this widely-used model.Unilateral knee surgery was performed in adult male Sprague-Dawley rats (n=5 with DMM, n=5 with sham surgery). Radio-opaque beads were implanted on their femur and tibia. 8 weeks following knee surgery, rat gait was recorded using the 3D²YMOX setup (Sanctorum et al. 2019, simultaneous acquisition of biplanar XRay videos and ground reaction forces).10 trials (1 per rat) were calibrated and processed in XMALab (Knörlein et al. 2016). Hindlimb bony landmarks were labeled on the XRay videos using transfer learning (Deeplabcut, Mathis et al. 2019; Laurence-Chasen et al. 2020).A generic OpenSim musculoskeletal model of the rat hindlimb (Johnson et al. 2008) was adapted to include a 3-degree-of-freedom knee. Inverse kinematics, inverse dynamics, static optimization of muscle forces, and joint reaction analysis were performed.In rats with DMM, knee adduction was lower compared to sham surgery. Ground reaction forces were less variable with DMM, resulting in less variability in joint external moments. The mediolateral ground reaction force was lower, resulting in lower hip adduction moment, thus less force was produced by the rectus femoris. Rats with DMM tended to break rather than propel, resulting in lower hip flexion moment, thus less force was produced by the semimembranosus. These results are consistent with lower knee contact forces in the anteroposterior and axial directions.These preliminary data indicate no overloading of the knee joint in rats with DMM, compared with sham surgery. We are currently expanding our workflow to finite element analysis, to examine mechanical cues in the cartilage of these rats (Fig1G).

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.

The effect of gait modification on the response of medial meniscus extrusion during gait in patients with knee osteoarthritis

BackgroundAn increase in medial meniscus extrusion during weight-bearing conditions is associated with the progression of medial knee osteoarthritis (OA). Toe-out gait modification has been known to reduce the knee adduction moment (KAM); however, its effect on reducing the increase in medial meniscus extrusion in patients with knee OA remains unclear. Research questionTo (1) evaluate the effect of toe-out gait on the increase in medial meniscus extrusion and the KAM in patients with medial knee OA and (2) investigate the synergetic effect of lateral wedge insoles in combination with toe-out gait in determining the most effective intervention for reducing medial meniscus extrusion during gait. MethodsTwenty-five patients with medial knee OA were enrolled in this study. Participants walked under four conditions: normal gait, toe-out gait, normal gait with lateral wedge insoles, and toe-out gait with lateral wedge insoles. Medial meniscus extrusion and KAM peaks during gait were measured using ultrasound and a three-dimensional motion analysis system in each condition. These parameters were compared among the four conditions using repeated measures analysis of variance. ResultsThe increase in medial meniscus extrusion and the second KAM peak were significantly lower in all interventions compared with those observed during normal gait. However, there was no significant difference among the interventions. SignificanceThis study suggested that toe-out gait reduces the increase in medial meniscus extrusion and is associated with the reduction of the second KAM peak. However, no synergistic effect of lateral wedge insoles and toe-out gait was observed.

Effect of transtibial prosthesis weight on the contralateral knee joint in relation to the risk of osteoarthritis.

Individuals with transtibial amputation place more load on the contralateral lower extremity. A higher adduction moment at the knee joint has been shown to have an effect on the risk of osteoarthritis. The aim of this study was to investigate the effect of weight-bearing of lower-limb prosthesis on the biomechanical parameters associated with the risk of contralateral knee osteoarthritis. Cross-sectional. The experimental group of 14 subjects with unilateral transtibial amputation (13 males). The mean age was 52.7 ± 14.2 years, height 175.6 ± 6.3 cm, weight 82.3 ± 12.5 kg, and duration of prosthesis use 16.5 ± 9.1 years. The control group consisted of 14 healthy subjects with identical anthropometric parameters. Dual emission X-ray absorptiometry was used to determine the weight of the amputated limb. For gait analysis, 10 Qualisys infrared cameras and a motion sensing system on 3 Kistler force platforms were used. Gait was analyzed with the original, lighter, commonly used prosthesis, as well as the prosthesis loaded to the original limb weight. The gait cycle and kinetic parameters of the amputated and healthy limbs were more similar to those of the control group when using the weighted prosthesis. We recommend further research to more accurately specify the weight of the lower-limb prosthesis with respect to the prosthesis design and duration of use of the heavier prosthesis during the day.

Exploring the modification factors of exercise therapy on biomechanical load in patients with knee osteoarthritis: a systematic review and meta-analysis.

The objective of this systematic review and meta-analysisis to clarify the effect of exercise therapy on the first peak knee adduction moment (KAM), as well as other biomechanical loads in patients with knee osteoarthritis (OA), and identify physical characteristics that influence differences in biomechanical load after exercise therapy. The data sources are PubMed, PEDro, and CINAHL, from study inception to May 2021. The eligibility criteria include studies evaluating the first peak (KAM), peak knee flexion moment (KFM), maximal knee joint compression force (KCF), or co-contraction during walking before and after exercise therapy in patients with knee OA. The risk of bias was independently assessed by two reviewers usingPEDro and NIH scales. Among 11 RCTs and nine non-RCTs, 1119 patients with knee OA were included (average age: 63.7 years). As the results of meta-analysis, exercise therapy tended to increase the first peak KAM (SMD 0.11; 95% CI: -0.03-0.24), peak KFM (SMD 0.13; 95% CI: -0.03-0.29), and maximal KCF (SMD 0.09; 95% CI -0.05-0.22). An increased first peak KAM was significantly associated with a larger improvement in knee muscle strength and WOMAC pain. However,the quality of evidence regarding the biomechanical loads was low-to-moderate according to the GRADE approach.The improvement in pain and knee muscle strength may mediate the increase in first peak KAM, suggesting difficulty in balancing symptom relief and biomechanical load reduction. Therefore, exercise therapy may satisfy both aspects simultaneously when combined with biomechanical interventions, such as a valgus knee brace or insoles. Registration: PROSPERO (CRD42021230966).

Walking with Different Insoles Changes Lower-Limb Biomechanics Globally in Patients with Medial Knee Osteoarthritis.

Using insoles to modify walking biomechanics is of keen interest for the treatment of medial-compartment knee osteoarthritis. So far, insole interventions have focused on reducing the peak of the knee adduction moment (pKAM) and have led to inconsistent clinical outcomes. This study aimed to evaluate the changes in other gait variables related to knee osteoarthritis when patients walk with different insoles to provide insights into the necessity to enlarge the biomechanical analyses to other variables. Walking trials were recorded for 10 patients in four insole conditions. Changes among conditions were computed for six gait variables, including the pKAM. The associations between the changes in pKAM and the changes in the other variables were also assessed individually. Walking with different insoles had noticeable effects on the six gait variables, with high heterogeneity among patients. For all variables, at least 36.67% of the changes were of medium-to-large effect size. The associations with the changes in pKAM varied among variables and patients. In conclusion, this study showed that varying the insole could globally influence ambulatory biomechanics and that limiting measurement to the pKAM could lead to an important loss of information. Beyond the consideration of additional gait variables, this study also encourages personalized interventions to address inter-patient variability.

Biomechanical Gender Differences in the Uninjured Extremity After Anterior Cruciate Ligament Reconstruction in Adolescent Athletes: A Retrospective Motion Analysis Study.

Introduction Subsequent anterior cruciate ligament (ACL) injury is more common in the pediatric population and encompasses graft failure and subsequent contralateral tears. Females are at a higher risk. The purpose of the present study was to compare the knee valgus angles at initial contact, knee extension moments, anterior and lateral knee joint forces, hip flexion angles, hip adduction moments, and ankle inversion during the drop vertical test in the uninjured extremity between adolescent males and females who had previously undergone an anterior cruciate ligament reconstruction (ACLR). Methods This IRB-approved retrospective chart review included patientsaged 8-18 years who were seen at the five to seven month postoperatively following ACL reconstruction. A total of 168 patients met our inclusion criteria (86 girls and 82 boys.) Using three-dimensional motion capture technology (CORTEX software, Motion Analysis Corp., Rohnert Park, CA), data were collected while the subject performed the drop vertical test over floor-mounted force plates (FP-Stairs, AMTI, Watertown, MA) under the direct supervision of a pediatric physical therapist. The Wilcoxon rank sum was used, and p < 0.05 was considered statistically significant. Results Females demonstrated a larger average knee joint extension moment (0.31 vs 0.28 N*m/kg, p = 0.0408), a larger anterior knee joint force at initial contact (3.51 vs. 2.79, N/kg, p = 0.0458), larger average hip flexion angle (41.50° vs. 35.99°, p = 0.0005), a smaller maximum hip adduction moment (0.92 vs. 1.16, N*m/kg, p = 0.0497), and a smaller average ankle inversion angle (5.08° vs. 6.41°, p = 0.03231). No significant differences were found regarding knee abduction angle or lateral knee joint force. Conclusions The biomechanical profile of the contralateral extremity varies significantly between the genders after ACLR. In the uninjured extremity, females may have larger hip flexion angles, smaller hip adduction moments, larger anterior knee joint forces, larger knee extension moments, and smaller ankle inversion angles as compared to males after ACLR. These findings may explain the higher incidence of subsequent contralateral injury in female adolescent athletes. Further work is required to develop a composite score that determines at-risk athletes.

Determining the optimal gait modification strategy for patients with knee osteoarthritis: Trunk lean or medial thrust?

BackgroundThe gait modification strategies Trunk Lean and Medial Thrust have been shown to reduce the external knee adduction moment (EKAM) in patients with knee osteoarthritis which could contribute to reduced progression of the disease. Which strategy is most optimal differs between individuals, but the underlying mechanism that causes this remains unknown. Research questionWhich gait parameters determine the optimal gait modification strategy for individual patients with knee osteoarthritis? MethodsForty-seven participants with symptomatic medial knee osteoarthritis underwent 3-dimensional motion analysis during comfortable gait and with two gait modification strategies: Medial Thrust and Trunk Lean. Kinematic and kinetic variables were calculated. Participants were then categorized into one of the two subgroups, based on the modification strategy that reduced the EKAM the most for them. Multiple logistic regression analysis with backward elimination was used to investigate the predictive nature of dynamic parameters obtained during comfortable walking on the optimal modification gait strategy. ResultsFor 68.1 % of the participants, Trunk Lean was the optimal strategy in reducing the EKAM. Baseline characteristics, kinematics and kinetics did not differ significantly between subgroups during comfortable walking. Changes to frontal trunk and tibia angles correlated significantly with EKAM reduction during the Trunk Lean and Medial Thrust strategies, respectively. Regression analysis showed that MT is likely optimal when the frontal tibia angle range of motion and peak knee flexion angle in early stance during comfortable walking are high (R2Nagelkerke = 0.12). SignificanceOur regression model based solely on kinematic parameters from comfortable walking contained characteristics of the frontal tibia angle and knee flexion angle. As the model explains only 12.3 % of variance, clinical application does not seem feasible. Direct assessment of kinetics seems to be the most optimal strategy for selecting the most optimal gait modification strategy for individual patients with knee osteoarthritis.

Peak knee joint moments accurately predict medial and lateral knee contact forces in patients with valgus malalignment

Compressive knee joint contact force during walking is thought to be related to initiation and progression of knee osteoarthritis. However, joint loading is often evaluated with surrogate measures, like the external knee adduction moment, due to the complexity of computing joint contact forces. Statistical models have shown promising correlations between medial knee joint contact forces and knee adduction moments in particularly in individuals with knee osteoarthritis or after total knee replacements (R2 = 0.44–0.60). The purpose of this study was to evaluate how accurately model-based predictions of peak medial and lateral knee joint contact forces during walking could be estimated by linear mixed-effects models including joint moments for children and adolescents with and without valgus malalignment. Peak knee joint moments were strongly correlated (R2 > 0.85, p < 0.001) with both peak medial and lateral knee joint contact forces. The knee flexion and adduction moments were significant covariates in the models, strengthening the understanding of the statistical relationship between both moments and medial and lateral knee joint contact forces. In the future, these models could be used to evaluate peak knee joint contact forces from musculoskeletal simulations using peak joint moments from motion capture software, obviating the need for time-consuming musculoskeletal simulations.

Cumulative knee adduction moment during jogging causes temporary medial meniscus extrusion in healthy volunteers.

The cumulative knee adduction moment (KAM) is a key parameter evaluated for the prevention of overload knee injuries on the medial compartment. Medial meniscus extrusion (MME), typical in hoop dysfunctions, is a measure for the cumulative mechanical stress in individual knees; however, its correlation with cumulative KAM is unknown. The aim of this study was to investigate the effect of temporary overload stress on MME and its correlation with cumulative KAM. Thirteen healthy asymptomatic volunteers (13 knees) were recruited for a cohort study (mean age, 23.1 ± 3.3years; males: n = 8). The cumulative KAM was calculated using a three-dimensional motion analysis system, in addition to the number of steps taken while jogging uphill or downhill. MME was evaluated using ultrasound performed in the standing position. The evaluations were performed four times: at baseline (T0), before and after (T1 and T2, respectively) jogging uphill or downhill, and 1day after (T3) jogging. Additionally, the Δ-value was calculated using the change of meniscus after efforts as the difference in MME between T1 and T2. The MME in T2 was significantly greater than those in T0 and T1. Conversely, the MME in T3 was significantly lesser than that in T2. No significant difference was found between those in T0 and T1, and T3. ΔMME exhibited a significant positive correlation with the cumulative KAM (r = 0.68, p = 0.01), but not for peak KAM. The temporary reaction of MME observed in ultrasound correlates with the cumulative stress of KAM.

Transverse plane gait variables are better predictors for knee adduction moment than CT-based measures of torsional deformities in children and adolescents

Transverse plane gait variables are better predictors for knee adduction moment than CT-based measures of torsional deformities in children and adolescents

Higher Association of Pelvis-Knee-Ankle Angle Compared With Hip-Knee-Ankle Angle With Knee Adduction Moment and Patient-Reported Outcomes After High Tibial Osteotomy

Background: High tibial osteotomy (HTO) reduces the load distribution of the medial compartment by modifying leg alignment. Knee adduction moment (KAM), a surrogate measure of dynamic loading in the knee joint, decreases after HTO. However, leg alignment does not fully account for KAM. Purpose: To assess the association between the pelvis-knee-ankle angle (PKA), a novel radiographic parameter reflecting leg alignment and pelvic width, and KAM and patient-reported outcomes after HTO. Study Design: Cross sectional study; Level of evidence, 3. Methods: PKA is the angle between the line from the midpoint of the anterior superior iliac spine to the center of the knee joint and the mechanical axis of the tibia. In this study, 54 patients with medial compartment knee osteoarthritis and varus alignment who underwent 3-dimensional gait analysis preoperatively and 2 years after medial open-wedge HTO were evaluated. The primary outcomes were hip-knee-ankle angle (HKA), PKA, KAM peaks, and Knee Society Score (KSS). Single and multivariate regression analysis including PKA and KAM peaks as well as other demographic and radiologic factors was performed. Results: HKA was weakly correlated with the first peak KAM (r = −0.33; P < .01) and second peak KAM (r = −0.27; P = .01) before HTO, but not significantly correlated after HTO. PKA was moderately correlated with the first peak KAM (r = 0.45; P < .01) and second peak KAM (r = 0.45; P < .01) before HTO and with the first peak KAM (r = 0.51; P < .01) and second peak KAM (r = 0.56; P < .01) after HTO. Multivariate linear regression revealed that postoperative PKA was still associated with the KAM peaks after HTO. Only postoperative PKA was correlated with the KSS satisfaction subscale (r = −0.30; P = .03). Conclusion: Although HKA was not correlated with KAM peaks after HTO, PKA was significantly correlated with KAM peaks in patients with varus knee osteoarthritis after HTO.

Hip joint function and reconstruction of the anterior femoral offset in patients with short stem vs. conventional THA

In cases where mobility and joint function are impaired after implantation of a THA, weakening of hip movement in both extension/flexion and adduction/abduction may play a role due to shortening of the physiological lever arm of the hip muscles. Mechanical factors of influence include the lateral femoral offset, which affects the lever arm, and the antetorsion angle of the hip prosthesis, which affects the anterior femoral offset. This study aimed to investigate the effect of an altered antetorsion angle of the implant on the hip moments and gait patterns of the patient. For this study, 13 patients with a conventional stem on one side and a calcar-guided short stem implanted on the contralateral side were included. To determine the maximum hip moment, tests were performed on a dynamometer in extension/flexion and adduction/abduction in addition to gait analysis. As a control, a comparison was made with data from a reference group of 30 healthy subjects. Both implants showed similar symmetry indices. There was a significant difference between the implants for adduction moments (p < 0.001). The ratios between the directions of moments showed no significant differences. The joint function measured by isokinetic measurements and gait analysis remains comparable to the healthy control group after short stem arthroplasty, but shows slight changes after conventional stem arthroplasty.

High tibiofemoral contact and muscle forces during gait are associated with radiographic knee OA progression over 3 years

BackgroundThe objective of this study was to investigate differences in tibiofemoral joint contact forces between individuals with moderate medial OA who exhibit radiographic knee OA progression within 3 years versus those who do not, and to understand the relationship between model-predicted contact forces and net external moments for this population. Methods27 individuals with moderate medial compartment knee OA underwent baseline instrumented gait analysis. OA progressors were defined as those who experienced at least a one grade increase in medial joint space narrowing at three years. An electromyography-driven musculoskeletal model was used to estimate muscle and tibiofemoral contact forces at baseline, which were compared between progressors and non-progressors using t-tests. ResultsSeven individuals experienced radiographic OA progression by 3 years. Progressors walked with significantly higher peaks of medial and total tibiofemoral contact forces, and higher impulse of medial contact forces. Significant and high correlations were found between: first peaks of medial and total contact forces with first peak of the knee adduction moment (R2 = 0.74; R2 = 0.59); second peaks of medial and total knee contact forces with second peaks of knee adduction and flexion moments (R2 = 0.71; R2 = 0.68); medial knee contact force impulse with knee adduction moment impulse (R2 = 0.76). ConclusionsHigher tibiofemoral joint contact forces during walking were associated with three-year radiographic knee OA progression based on medial joint space narrowing. These results support the need for strategies that reduce compressive knee contact forces through the reduction of adduction and flexion moments during walking.

Evaluation of the Effect of Knee Unloader Orthoses, Lateral Wedge Insoles, and Ankle Foot Orthoses on Pain, Function, and Knee Adduction Moment in Subjects with Medial Compartment Knee Osteoarthritis: A Literature Review

ABSTRACT Introduction Osteoarthritis (OA) is a destructive joint disease and a major cause of pain in the elderly. The use of supportive orthoses including valgus knee brace, lateral wedged insole, and ankle-foot orthosis (AFO) is a common treatment for these people. The purpose of this review of the literature is to evaluate the effect of orthoses on pain, function, and adduction moment (AM) of individuals with medial knee OA. Method The search was conducted among articles published from 2010 to 2021 in bibliographic online databases including ISI Web of Science, PubMed, Scopus, and Google Scholar. The potential titles and abstracts were reviewed based on the study inclusion criteria. All randomized controlled trial (RCT) studies on the effectiveness of valgus knee brace, AFO, and lateral wedged insoles in subjects with medial knee OA were reviewed. The search terms were OA, medial knee osteoarthritis, medial joint arthritis, unloader knee brace, valgus knee brace, knee sleeve, lateral wedge insole, AFO, ankle-foot orthosis, function, pain, alignment, kinetic, kinematic, and AM. Result Forty-two articles were reviewed to determine the current research process. Thirteen studies evaluated the effect of lateral wedge insole on pain, function, and AM in subjects with medial compartment knee OA. Ten studies evaluated unloader knee braces. Nine studies evaluated unloader knee brace compared with lateral wedge insole, three studies evaluated AFO, and seven studies examined the combination of knee braces and lateral wedge insoles on pain, function, and AM. Conclusion All three orthoses in short-term follow-up reduced the AM in subjects with medial knee OA. Lateral wedge insoles did not support pain reduction in studies. The results of this study showed that knee braces may have a more lasting effect on the knee joint in the long run than lateral wedge insoles. Although the number of studies that evaluated the effect of AFOs on outcomes of subjects with knee OA is low, this intervention was found to be effective in relieving pain and reducing AM. Clinical Relevance In clinical studies, clinical relevance in patients with medial knee OA, orthoses effectively reduced external knee AM and pain sensation during daily activities. Thus, use of orthoses effectively supports conservative treatment in medial knee OA.

IMU and Smartphone Camera Fusion for Knee Adduction and Knee Flexion Moment Estimation During Walking

Wearable sensing and computer vision could move biomechanics from specialized laboratories to natural environments, but better algorithms are needed to extract meaningful outcomes from these emerging modalities. In this article, we present new models for estimating biomechanical outcomes—the knee adduction moment (KAM) and knee flexion moment (KFM)—from fusion of smartphone cameras and wearable inertial measurement units (IMUs) among young healthy nonobese males. A deep learning model was developed to extract features, fuse multimodal data, and estimate KAM and KFM. Walking data from 17 subjects were recorded with eight IMUs and two smartphone cameras. The model that used IMU-camera fusion was significantly more accurate than those using IMUs or cameras alone. The root-mean-square errors of the fusion model were 0.49 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%\;\mathbf {BW}\cdot \mathbf {BH}$</tex-math></inline-formula> for KAM and 0.66 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%\;\mathbf {BW}\cdot \mathbf {BH}$</tex-math></inline-formula> for KFM estimation, which are lower than clinically significant thresholds. With larger and more diverse data, this model could enable assessment of knee moments in clinics and homes.

Limb alignment changes with knee flexion: A study based on CAS data

BackgroundRecent evidence has questioned the value of standing limb alignment for predicting the adduction moment and forces exerted on healthy and prosthetic knees. The purpose of this study was to assess the lower limb alignment of OA knee patients at various knee flexion angles.The main hypothesis was that lower limb alignment measured throughout knee flexion does not significantly differ between patients displaying different extension alignment (neutral, varus or valgus). Methods206 arthritic knee patients undergoing computer-assisted total (CAS) knee prosthesis were included. Frontal limb alignment was assessed in a systematic manner by CAS at three knee positions: extension, 90 degrees of flexion and maximal flexion. The HKA angle at each knee position and the change in HKA angle between two knee positions (delta value) were reported and compared. ResultsA large proportion of OA patients had significant variation in their lower limb alignment (32% with Δ HKA > 5°). The extended limb deformity tended to reduce with knee flexion: mean of 5° and 6° deformity reduction for varus and valgus patients, 40% and 66% of varus and valgus patients progressed to neutral alignment with 90° knee flexion. Forty percent of neutral extended lower limb did not maintain their neutral alignment but rather progressed to either varus or valgus at 90° knee flexion. ConclusionsLimb alignment in extension is a poor predictor of limb alignment in flexion in OA patients.Only considering the traditional frontal alignment of an extended lower limb for planning knee arthroplasty or osteotomy is likely insufficient.

Prediction of knee adduction moment using innovative instrumented insole and deep learning neural networks in healthy female individuals

BackgroundThe knee adduction moment, a biomechanical risk factor of knee osteoarthritis, is typically measured in a gait laboratory with expensive equipment and inverse dynamics modeling software. We aimed to develop a framework for a portable knee adduction moment estimation for healthy female individuals using deep learning neural networks and custom instrumented insole and evaluated its accuracy compared to the standard inverse dynamics approach. MethodsFeed-forward, convolutional, and recurrent neural networks were applied to the data extracted from five piezo-resistive force sensors attached to the insole of a shoe. ResultsAll models predicted knee adduction moment variables during walking with high correlation coefficients, r > 0.72, and low root mean squared errors (RMSE), ranging from 0.5% to 1.2%. The convolutional neural network is the most accurate predictor of average knee adduction moment (r = 0.96; RMSE = 0.5%) followed by the recurrent and feed-forward neural networks. ConclusionThese findings and the methods presented in the current study are expected to facilitate a cost-effective clinical analysis of knee adduction moment for healthy female individuals and to facilitate future research on prediction of other biomechanical risk factors using similar methods.

The biomechanical effects of insoles with different cushioning on the knee joints of people with different body mass index grades.

Background: Enhancing knee protection for individuals who are overweight and obese is crucial. Cushioning insoles may improve knee biomechanics and play a significant protective role. However, the impact of insoles with varying cushioning properties on knee joints in individuals with different body mass index (BMI) categories remains unknown. Our aim was to investigate the biomechanical effects of insoles with different cushioning properties on knee joints across different BMI grades. Methods: Gravity-driven impact tests were used to characterize the cushioning properties of three types of Artificial Cartilage Foam (ACF18, 28, and 38) and ethylene-vinyl acetate (EVA) insoles. Knee joint sagittal, coronal, and vertical axis angles and moments were collected from healthy-weight (BMI 18.5-23.9kg/m2, n = 15), overweight (BMI 24.0-27.9kg/m2, n = 16), and obese (BMI ≥28.0kg/m2, n = 15) individuals randomly assigned four different insoles during a drop jump. The Kruskal-Wallis test and mixed model repeated measures analysis of variance were used to compare differences among cushioning and biomechanical data across various insoles, respectively. Results: ACF showed higher cushioning than EVA, and ACF38 was the highest among the three types of ACF (all p < 0.001). During the drop jump, the knee flexion angles and moments of the ACF insoles were lower than those of the EVA insoles, the knee adduction angles of the ACF18 and ACF28 insoles were lower than those of the EVA insoles, and ACF18 insoles increased the first cushion time (all p < 0.05) for all participants in whom biomechanical variables demonstrated no interactions between insoles and BMI. Regarding the BMI-dependent biomechanical variables, compared with the EVA insoles, ACF28 insoles decreased the knee flexion angle and ACF38 insoles decreased the knee adduction and rotation moment in the healthy-weight group; ACF18 insoles decreased the knee flexion angle and ACF38 insoles decreased the knee moment in the overweight group; ACF28 insoles decreased the knee flexion and adduction moment, and ACF38 insoles decreased the knee flexion angle and rotation moment in the obese group (all p < 0.05). Conclusion: Insoles with higher cushioning properties could improve knee biomechanics and provide better knee joint protection in people across different BMI ranges.