Association Between Knee Joint Muscle Activation and Knee Joint Moment Patterns During Walking in Moderate Medial Compartment Knee Osteoarthritis: Implications for Secondary Prevention.

OBJECTIVE: To determine associations between knee moment features linked to osteoarthritis (OA) progression, gait muscle activation patterns, and strength. DESIGN: Cross-sectional secondary analysis. SETTING: Gait laboratory. PARTICIPANTS: Convenience sample of 54 patients with moderate, medial knee OA (N=54). INTERVENTIONS: None. MAIN OUTCOME MEASURES: Knee moments and quadriceps and hamstrings activation were examined during walking. Knee extensor and flexor strength were measured. Waveform patterns were extracted using principal component analysis. Each measured waveform was scored against principal components (PCs) that captured overall magnitude (PC1) and early to midstance difference (PC2) features, with higher PC2 scores interpreted as greater moment differential and more prolonged muscle activity. Correlations were calculated between moment PC scores and muscle PC and strength scores. Regression analyses determined moment PC score variance explained by muscle PC scores and strength. RESULTS: All correlations for knee adduction moment difference feature (KAMPC2) and prolonged muscle activity (PC2) were significant (r=-0.40 to -0.54). Knee flexion moment difference feature (KFMPC2) was significantly correlated with all quadriceps and medial hamstrings PC2 scores (r=-0.47 to -0.61) and medial hamstrings magnitude feature (PC1) (r=-0.52). KAMPC2 was significantly correlated with knee flexor strength (r=0.43), and KFMPC2 was significantly correlated with knee extensor (r=0.60) and flexor (r=0.55) strength. Regression models including muscle PC2 scores and knee flexor strength explained 46% of KAMPC2 variance, whereas muscle PC2 scores and knee extensor strength explained 59% of KFMPC2 variance. CONCLUSIONS: Muscle activation patterns and strength explained significant variance in moment difference features, highest for the knee flexion moment. This supports that exercises such as neuromuscular training, focused on appropriate muscle activation patterns, and strengthening have the potential to alter dynamic loading gait patterns associated with knee OA clinical progression.

Does body size impact muscle recruitment during law enforcement physical control simulator use?

This study examined muscle activation during the 'push-pull' component of law enforcement physical abilities testing and assessed activation differences based on sex, height, and body mass index. Fifty participants (40 male) completed the 'push-pull' task while surface electromyograms were recorded from ten upper and lower extremity muscles, and six trunk muscles. Muscle activation was amplitude-normalized to maximum voluntary isometric contraction and compared between sexes and tertiles of height and body mass index (BMI). Women had significantly higher activation of anterior deltoid and pectoralis major on the pull, and posterior deltoid and triceps on the push. Significant differences largely remained after controlling for body size in regression analyses. The lowest tertile of height had significantly higher triceps activity on the push. The highest tertile of BMI had significantly higher rectus abdominus and external obliques activity on the pull, and external obliques activation on the push. Practitioner summary: Muscle activation during the 'push-pull' component of law enforcement standardised testing was examined, including differences based on sex, height, and BMI. Minimal differences existed between sexes (females had higher deltoid, pectoralis major, triceps activity), height (shorter people had higher triceps activity) and BMI tertiles (larger people had more abdominal activity). Abbreviations: ANOVA: analysis of variance; BMI: body mass index; COPAT: correctional officer's physical abilities test; EMG: electromyogram; IMU: inertial measurement unit; MVIC: maximum voluntary isometric contraction; PARE: physical abilities requirement evaluation; PCS: physical control simulator; POPAT: police officer's physical abilities test; RMS: root mean square.

The Effects of a Heel Wedge on Hip, Pelvis and Trunk Biomechanics During Squatting in Resistance Trained Individuals.

Barbell back squats are a popular exercise for developing lower extremity strength and power. However, this exercise has potential injury risks, particularly to the lumbar spine, pelvis, and hip joint. Previous literature suggests heel wedges as a means of favorably adjusting trunk and pelvis kinematics with the intention of reducing such injury risks. Yet no direct biomechanical research exists to support these recommendations. Therefore, the purpose of this study was to examine the effects of heel wedges compared with barefoot on minimally loaded barbell back squats. Fourteen trained male participants performed a barbell back squat in bare feet or with their feet raised bilaterally with a 2.5-cm wooden block while 3-dimensional kinematics, kinetics, and electromyograms were collected. The heel wedge condition elicited significantly less forward trunk flexion angles at peak knee flexion, and peak external hip joint moments (p ≤ 0.05) compared with barefoot conditions. However, no significant differences were observed between conditions for trunk and pelvis angle differences at peak knee flexion (p > 0.05). Lastly, no peak or root mean square differences in muscle activity were elicited between conditions (p > 0.05). Our results lend support for the suggestions provided in literature aimed at using heel wedges as a means of reducing excessive forward trunk flexion. However, the maintenance of a neutral spine, another important safety factor, is not affected by the use of heel wedges. Therefore, heel wedges may be a viable modification for reduction of excessive forward trunk flexion but not for reduction in relative trunk-pelvis flexion during barbell back squats.

The Biomechanical Demands on the Hip During Progressive Stepping Tasks.

Hatfield, GL, Charlton, JM, Cochrane, CK, Hammond, CA, Napier, C, Takacs, J, Krowchuk, NM, and Hunt, MA. The biomechanical demands on the hip during progressive stepping tasks. J Strength Cond Res 31(12): 3444-3453, 2017-Functional hip strengthening exercises are important components of lower extremity (LE) rehabilitation and include single-leg squats (SLS), step-downs (SD), and step-ups (SU). The biomechanical demand of these tasks is unclear. This repeated-measures study determined hip biomechanical demands in a healthy population. Twenty individuals (10 men, 26.6 ± 5.1 years, 22.1 ± 2.3 kg·m) participated. Three-dimensional motion, ground reaction force data, and surface electromyograms (EMG) were recorded during 4 randomly ordered tasks. Outcomes included frontal and sagittal plane hip moment impulses and muscle activity for each task. Repeated measures analysis of variance models (alpha = 0.05) determined between-task differences. Step-down and SLS were most biomechanically demanding, with significantly higher hip flexion and adduction moment impulses, and gluteus medius (GM) and quadriceps activity compared with half step-down (HSD) and SU. No significant difference was found between SD and SLS, indicating minimal difference in demand between the 2 tasks, likely due to kinematic similarities in performance; there were no significant differences in knee or hip sagittal plane angle excursion, or peak pelvic obliquity angle between the 2 tasks. Step-up was least demanding, with the lowest hip flexion and adduction moment impulses and GM, quadriceps, and hamstrings activity. Step-up was least demanding on the hip and would be a good starting task for hip strengthening protocols. Step-down and SLS were most demanding, requiring higher hip moments and muscle activity. These results provide evidence, which may be used in planning of progressive rehabilitation programs for patients with LE pathologies.

Psychological and physiological effects of an acute bout of yoga before a simulated academic exam in university students.

Objective: Test anxiety is common among nursing students. Yoga is one form of physical activity which may be beneficial for pretest anxiety. Participants: Thirteen undergraduate students (85% nursing majors, 15% awaiting program entry, 20 ± 4.9 years of age) completed the crossover design study. Methods: Participants completed a yoga or control intervention (independent quiet study) on opposing testing days. At three time points, participants provided ratings of anxiety (visual analog scales), saliva samples for cortisol and alpha amylase, and seated heart rate variability (HRV, time and frequency domains) was recorded. Results: Yoga prior to a simulated exam had a positive impact on subjective measures of stress but did not positively impact cortisol or HRV compared to the control condition. Conclusions: There may be benefits to participating in 30 min of moderate intensity yoga for reduced perception of stress before a scholarly examination. Further research regarding the impacts of acute yoga on physiological measures of HRV and/or cortisol are warranted.

Moms on the move: A qualitative exploration of a postpartum group exercise program on physical activity behaviour at three distinct time points.

PURPOSE: Physical activity (PA) after the birth of a child is associated with improved physical and mental health benefits. The aim of the study was to explore new mothers' experiences of PA before and after participation in a group-based PA program for new mothers. The study has three research questions: how new mothers felt; 1) about PA after the birth of their child 2) about engaging in a group-based PA program and 3) after the program ended about ongoing PA engagement. METHODS: We conducted an 8-week bi-weekly PA program for postpartum women. To understand the experience of postpartum women engaging in a group-based PA program we conducted one-on-one semi-structured interviews before, after, and at 6-month follow-up. RESULTS: Of the n = 21 participants in the Moms on the Move study; n = 17 completed pre interviews.s. One primary theme emerged from pre-program interviews where mothers shared how they were lost as to where to start PA. Post-program interviews produced two primary themes; engaging in PA helped mothers, and mothers learned to rethink PA. CONCLUSIONS: Postpartum women who participated in this group-based PA program had positive benefits to their mental and physical health and were able to alter their PA behaviour.

The effect of total knee arthroplasty on knee joint kinematics and kinetics during gait.

This study determined how total knee arthroplasty (TKA) altered knee motion and loading during gait. Three-dimensional kinematic and kinetic gait patterns of 42 patients with severe knee osteoarthritis were collected 1 week prior and 1-year post-TKA. Principal component analysis extracted major patterns of variability in the gait waveforms. Overall and midstance knee adduction moment magnitude decreased. Overall knee flexion angle magnitude increased due to an increase during swing. Increases in the early stance knee flexion moment and late stance knee extension moment were found, indicating improved impact attenuation and function. A decrease in the early stance knee external rotation moment indicated alteration in the typical rotation mechanism. Most changes moved toward an asymptomatic pattern and would be considered improvements in motion, function, and loading.

Baseline Gait Muscle Activation Patterns Differ for Osteoarthritis Patients Who Undergo Total Knee Arthroplasty Five to Eight Years Later From Those Who Do Not.

OBJECTIVE: To determine if baseline quadriceps and hamstrings muscle activity patterns differed between those with medial-compartment knee osteoarthritis (OA) who advanced to total knee arthroplasty (TKA) and those who did not advance to TKA, and to examine associations between features extracted from principal component analysis (PCA) and discrete measures. METHODS: Surface electromyograms of the vastus lateralis and medialis, rectus femoris, and lateral and medial hamstrings during walking were collected from 54 individuals with knee OA. Amplitude and temporal characteristics from PCA, co-contraction indices (CCI) for lateral and medial muscle pairs, and root mean square (RMS) amplitudes for early, mid, late, and overall stance were calculated from electromyographic waveforms. At follow-up 5 to 8 years later, 26 participants reported having undergone TKA. Analysis of variance models tested for differences in principal component (PC) scores and discrete measures between TKA and no-TKA groups (α = 0.05). Pearson's product moment correlation coefficients were calculated between PC scores and discrete variables. RESULTS: The TKA group had higher hamstrings activity magnitudes (PC1), prolonged activity in mid stance (PC2) for all muscles, and greater lateral CCI. TKA had higher RMS hamstrings activity for all stance phases, and higher RMS mid- and late-stance quadriceps activity. PC1 was highly correlated with RMS amplitude (highest overall and early stance). PC2 was correlated with mid- and late-stance RMS. CCIs were correlated with PC1 and PC2, with greater variance explained for PC1. CONCLUSION: Those who advanced to TKA had higher magnitudes and more prolonged agonist and antagonist activity, consistent with less joint unloading. These gait muscle activation patterns indicate a potential conservative intervention target.

Temporal coactivation of abdominal muscles during dynamic stability exercises.

The purpose of this study was to determine abdominal muscle temporal responses to a leg-loading exercise protocol and if differences exist between those able and unable to minimize lumbar-pelvic motion during this protocol. The focus was a supine bilateral leg-loading task that incorporated a slide (level 4) or no slide (level 5). Thirty-three healthy subjects (mean age 24 years) completed the task while surface electromyograms (EMG) from 5 abdominal muscle sites were recorded. Subjects were assigned to stable or unstable groups based on their ability to minimize lumbar-pelvic motion. After time and amplitude normalization, electromyography waveforms were entered into a pattern recognition procedure and scores for each principal pattern were calculated. Four principal patterns explained 90% of variance in the waveform data, with these principal patterns capturing the mean pattern, the relative amplitude change during the leg-extension phase, and subtle changes in shape throughout the exercise. Significant interactions (p < 0.05) were found for principal patterns; 1, 2, and 4 scores; and significant main (p < 0.05) effects for principal pattern 3 scores. These results illustrate temporal synchrony among the abdominal wall muscle activation during the bilateral leg-loading tasks; however, there was less variability in the activation patterns during the leg-lift and leg extension-phases for those who were able to minimize lumbar-pelvic motion compared to those who were unable to perform the task correctly. These results illustrate the need to focus on coordinated recruiting of the abdominal wall muscles in an organized manner and not simply increasing the intensity of activation for stabilization training.

Ankle Joint and Rearfoot Biomechanics During Toe-In and Toe-Out Walking in People With Medial Compartment Knee Osteoarthritis.

BACKGROUND: Toe-in and toe-out walking are 2 strategies that have been shown to be effective in reducing the knee adduction moment in people with knee osteoarthritis. However, despite a positive biomechanical impact on the knee, altering foot rotation may impart unintended forces or joint positions on the ankle that could impact joint health. The kinematic and kinetic changes at the ankle during toe-in or toe-out walking have yet to be examined. OBJECTIVE: To examine ankle/rearfoot biomechanics during toe-in and toe-out walking in those with knee osteoarthritis. DESIGN: Single-session repeated measures design to compare ankle biomechanics during walking with 4 different foot rotations. SETTING: University motion analysis laboratory. PARTICIPANTS: A convenience sample (N = 15) of males and females with a diagnosis of medial knee osteoarthritis confirmed by radiographs. METHODS: Participants walked in 4 conditions guided by real-time biofeedback: (1) toe-in (+10°), (2) zero rotation (0°), (3) toe-out (-10°), and (4) toe-out (-20°). Ankle and rearfoot kinematics and kinetics were examined during barefoot over-ground walking. MAIN OUTCOME MEASURES: Ankle joint angles, moments, moment impulses, and foot rotation. RESULTS: Overall, toe-in compared to toe-out walking decreased (P = .03) peak rearfoot eversion (toe-in = -1.6°; 10° toe-out = -3.7°; 20° toe-out = -4.1°). Toe-in compared to toe-out walking also increased rearfoot inversion at initial contact (7.4° vs 3.1° at 10° toe-out and 1.9° at 20° toe-out; P < .001) and frontal plane rearfoot angle excursion (9.0° vs 6.8° at 10° toe-out and 6.0° at 20° toe-out; P < .006). Toe-in compared to all other conditions increased peak external ankle inversion moments (0.04 Nm/kg vs 0.02 Nm/kg at 0°, 0.02 Nm/kg at 10° toe-out, and 0.01 Nm/kg at 20° toe-out; P < .003). CONCLUSIONS: Toe-in and toe-out walking require different ankle/rearfoot biomechanics, though no differences in discomfort were observed. Longer-term studies are required to properly assess these relationships in knee osteoarthritis populations. LEVEL OF EVIDENCE: IV.

Toe-in and toe-out walking require different lower limb neuromuscular patterns in people with knee osteoarthritis.

Toe-in and toe-out gait modification has received attention lately as a promising treatment for knee osteoarthritis due to its potential to improve knee joint loading and pain. However, the neuromuscular patterns associated with these walking styles are not well known, a factor that may influence knee joint load itself. Our aim was to conduct a thorough examination of the neuromuscular patterns associated with toe-in and toe-out walking in people with knee osteoarthritis. Fifteen participants were instructed to walk in four different foot rotations: 10° toe-in, 0°, as well as 10° and 20° toe-out. Nine surface electrodes were placed over lower extremity muscles and a variety of muscle activation parameters were examined. Peak and average medial hamstrings muscle activation was increased (p = 0.001, p < 0.001) during toe-in walking compared to toe-out walking. As well, average lateral gastrocnemius muscle activation was higher (p = 0.001) during toe-in walking compared to 20° toe-out. Medial thigh muscle co-contraction was higher (p = 0.003) during toe-in walking compared to all other conditions, and medial to lateral gastrocnemius activation ratio was lower (p = 0.032) during toe-in walking. These findings suggest potential overall increased joint loading with toe-in walking as a result of muscle co-contraction. Long-term assessment of these strategies is warranted.

Contralateral limb foot rotation during unilateral toe-in or toe-out walking in people with knee osteoarthritis.

BACKGROUND: Gait modification is a treatment approach often used for a variety of neuromuscular and musculoskeletal pathologies. Gait modification is commonly applied to a single limb, as is done with foot rotation (FR) in people with knee osteoarthritis (KOA). However, the extent to which gait changes observed in the trained limb are also exhibited in the untrained, contralateral limb during a training session is unknown. RESEARCH QUESTION: The purpose of this study was to examine the within-limb FR differences across four unilateral FR modifications compared to natural walking. METHODS: Sixteen individuals with KOA walked on a treadmill while performing four different FR conditions: 10° toe-in, 0°, 10° toe-out and 20° toe-out. Motion capture was conducted to track FR magnitude after five minutes of practice. RESULTS: The change in contralateral FR angle compared to natural walking significantly increased during toe-in 10° walking (3.1°) compared to toe-out -10° and -20° walking (-1.2° and -1.5°, respectively). As expected, the ipsilateral FR angle was significantly different between all conditions. SIGNIFICANCE: These results suggest that small, but statistically significant changes in the untrained contralateral limb FR are observed during FR training of the ipsilateral limb. This may indicate a desire for symmetry, or a compensation when modifying the ipsilateral limb. Therefore, clinicians may need to maintain baseline FR magnitudes in the untrained limb when a patient exhibits unilateral KOA characteristics or lateral compartment KOA.

Ankle and knee biomechanics during normal walking following ankle plantarflexor fatigue.

The purpose of this study was to investigate the immediate effects of unilateral ankle plantarflexor fatigue on bilateral knee and ankle biomechanics during gait. Lower leg kinematics, kinetics, and muscle activation were assessed before and after an ankle plantarflexor fatiguing protocol in 31 healthy individuals. Fatigue (defined as >10% reduction in maximal isometric ankle plantarflexor torque production and a downward shift in the median power frequency of both heads of the gastrocnemius muscle of the fatigued limb) was achieved in 18 individuals, and only their data were used for analysis purposes. Compared to pre-fatigue walking trials, medial gastrocnemius activity was significantly reduced in the study (fatigued) limb. Other main changes following fatigue included significantly more knee flexion during loading, and an associated larger external knee flexion moment in the study limb. At the ankle joint, participants exhibited significantly less peak plantarflexion (occurring at toe-off) with fatigue. No significant differences were observed in the contralateral (non-fatigued) limb. Findings from this study indicate that fatigue of the ankle plantarflexor muscle does not produce widespread changes in gait biomechanics, suggesting that small to moderate changes in maximal ankle plantarflexor force production capacity (either an increase or decrease) will not have a substantial impact on normal lower limb functioning during gait.

Lateral wedges with and without custom arch support for people with medial knee osteoarthritis and pronated feet: an exploratory randomized crossover study.

BACKGROUND: Pronated foot posture is associated with many clinical and biomechanical outcomes unique to medial compartment knee osteoarthritis (OA). Though shoe-worn insole treatment, including lateral wedges, is commonly studied in this patient population, their effects on the specific subgroup of people with medial knee OA and concomitant pronated feet are unknown. The purpose of this study was to evaluate whether lateral wedge insoles with custom arch support are more beneficial than lateral wedge insoles alone for knee and foot symptoms in people with medial tibiofemoral knee osteoarthritis (OA) and pronated feet. METHODS: Twenty-six people with pronated feet and symptomatic medial knee OA participated in a randomized crossover study comparing five degree lateral wedge foot insoles with and without custom foot arch support. Each intervention was worn for two months, separated by a two-month washout period of no insoles wear. Main outcomes included the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain and physical function subscales, the revised short-form Foot Function Index (FFI-R) pain and stiffness subscales, and the timed stair climb test. Regression modeling was conducted to examine treatment, period, and interaction effects. RESULTS: Twenty-two participants completed the study, and no carryover or interaction effects were observed for any outcome. Significant treatment effects were observed for the timed stair climb, with greater improvements seen with the lateral wedges with arch support. Within-condition significant improvements were observed for WOMAC pain and physical function, as well as FFI-R pain and stiffness with lateral wedges with arch support use. More adverse effects were reported with the lateral wedges alone, while more people preferred the lateral wedges with arch support overall. CONCLUSIONS: Addition of custom arch support to a standard lateral wedge insole may improve foot and knee symptoms in people with knee OA and concomitant pronated feet. These preliminary findings suggest further research evaluating the role of shoe-worn insoles for treatment of this specific sub-group of people with knee OA is warranted. TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT02234895.

Trunk and lower limb biomechanics during stair climbing in people with and without symptomatic femoroacetabular impingement.

BACKGROUND: Femoroacetabular impingement is a pathomechanical hip condition leading to pain and impaired physical function. It has been shown that those with femoroacetabular impingement exhibit altered gait characteristics during level walking and stair climbing, and decreased muscle force production during isometric muscle contractions. However, no studies to-date have looked at trunk kinematics or muscle activation during dynamic movements such as stair climbing in this patient population. The purpose of this study was to compare biomechanical outcomes (trunk and lower limb kinematics as well as lower limb kinetics and muscle activation) during stair climbing in those with and without symptomatic femoroacetabular impingement. METHODS: Trunk, hip, knee and ankle kinematics, as well as hip, knee and ankle kinetics and muscle activity of nine lower limb muscles were collected during stair climbing for 20 people with clinical and radiographic femoroacetabular impingement and compared to 20 age- and sex-matched pain-free individuals. FINDINGS: Those with femoroacetabular impingement ascended the stairs slower (effect size=0.82), had significantly increased peak trunk forward flexion angles (effect size=0.99) and external hip flexion moments (effect size=0.94) and had decreased peak external knee flexion moments (effect size=0.90) compared to the control group. INTERPRETATION: Findings from this study indicate that while those with and without femoroacetabular impingement exhibit many biomechanical similarities when ascending stairs, differences in trunk forward flexion and joint kinetics indicate some important differences. Further longitudinal research is required to elucidate the cause of these differences as well as the clinical relevance.

Clinical Tests of Standing Balance in the Knee Osteoarthritis Population: Systematic Review and Meta-analysis.

BACKGROUND: People with knee osteoarthritis (OA) have a high prevalence of falls. Poor standing balance is one risk factor, but the extent of standing balance deficits in people with knee OA is unknown. PURPOSE: The primary purpose of this study was to summarize available data on standing balance in people with knee OA compared with people without knee OA. A secondary purpose was to establish the extent of balance impairment across disease severity. DATA SOURCES: A literature search of the MEDLINE, EMBASE, CINAHL, and Web of Science databases through November 19, 2014, was conducted. STUDY SELECTION: Studies on individuals with knee OA containing clinical, quantifiable measures of standing balance were included. Methodological quality was assessed by 2 reviewers using a 16-item quality index developed for nonrandomized studies. Studies scoring >50% on the index were included. DATA EXTRACTION: Participant characteristics (age, sex, body mass index, OA severity, compartment involvement, unilateral versus bilateral disease) and balance outcomes were extracted by 2 reviewers. Standardized mean differences were pooled using a random-effects model. DATA SYNTHESIS: The search yielded 2,716 articles; 8 met selection and quality assessment criteria. The median score on the quality index was 13/17. People with knee OA consistently performed worse than healthy controls on the Step Test, Single-Leg Stance Test, Functional Reach Test, Tandem Stance Test, and Community Balance and Mobility Scale. The pooled standardized mean difference was -1.64 (95% confidence interval=-2.58, -0.69). No differences were observed between varying degrees of malalignment, or between unilateral versus bilateral disease. LIMITATIONS: No studies compared between-knee OA severities. Thus, expected changes in balance as the disease progresses remain unknown. CONCLUSIONS: Few studies compared people with knee OA and healthy controls, but those that did showed that people with knee OA performed significantly worse. More research is needed to understand the extent of balance impairments in people with knee OA using easy-to-administer, clinically available tests.

Knee and ankle biomechanics with lateral wedges with and without a custom arch support in those with medial knee osteoarthritis and flat feet.

UNLABELLED: This study compared immediate changes in knee and ankle/subtalar biomechanics with lateral wedge orthotics with and without custom arch support in people with knee osteoarthritis and flat feet. Twenty-six participants with radiographic evidence of medial knee osteoarthritis (22 females; age 64.0 years [SD 8.0 years], BMI 27.2 kg/m(2) [4.2]) and flat feet (median foot posture index = + 5) underwent three-dimensional gait analysis for three conditions: Control (no orthotic), lateral wedge, and lateral wedge plus arch support. Condition order was randomized. Outcomes included frontal plane knee and ankle/subtalar biomechanics, and comfort. Compared to the control, lateral wedge and lateral wedge with arch support reduced the knee adduction moment impulse by 8% and 6%, respectively (p < 0.05). However, the lateral wedge resulted in a more everted foot position (4.3 degrees) than lateral wedge plus arch support (3.2 degrees) (p < 0.05). In contrast, lateral wedge plus arch support reduced foot frontal plane excursion compared to other conditions (p < 0.05). Participants self-reported significantly more immediate comfort with lateral wedge plus arch support compared to the control, whereas there was no difference in self-reported comfort between lateral wedge and control. No immediate changes in knee pain were observed in any condition. CLINICAL SIGNIFICANCE: Rather than prescribing lateral wedges to all patients with knee osteoarthritis, those who have medial knee osteoarthritis and flat feet may prefer to use the combined orthotic to reduce loads across the knee, and to minimize the risk of foot and ankle symptoms as a consequence of orthotic treatment. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1597-1605, 2016.

Relationship between knee adduction moment patterns extracted using principal component analysis and discrete measures with different amplitude normalizations: Implications for knee osteoarthritis progression studies.

BACKGROUND: Knee adduction moment discrete features (peaks and impulses) are commonly reported in knee osteoarthritis gait studies, but they do not necessarily capture loading patterns. Principal component analysis extracts dynamic patterns, but can be difficult to interpret. This methodological study determined relationships between external knee adduction moment discrete measures and principal component analysis features, and examined whether amplitude-normalization methods influenced differences in those with knee osteoarthritis who progressed to surgery versus those that did not. METHODS: 54 knee osteoarthritis patients had three-dimensional biomechanical measures assessed during walking. Knee adduction moments were calculated and non-normalized and amplitude-normalized waveforms using two common methods were calculated. Patterns were extracted using principal component analysis. Knee adduction moment peak and impulse were calculated. Correlation coefficients were determined between two knee adduction moment patterns extracted and peak and impulse. T-tests evaluated between-group differences. FINDINGS: An overall magnitude pattern was correlated with peak (r=0.88-0.90, p<0.05) and impulse (r=0.93, p<0.05). A pattern capturing a difference between early and mid/late -stance knee adduction moment was significantly correlated with peak (r=0.27-0.40, p<0.05), but explained minimal variance. Between-group peak differences were only affected by amplitude-normalization method. INTERPRETATION: Findings suggest that the overall magnitude knee adduction moment principal pattern does not provide unique information from peak and impulse measures. However, low correlations and minimal variance explained between the pattern capturing ability to unload the joint during mid-stance and the two discrete measures, suggests that this pattern captured a unique waveform feature.

Three-dimensional biomechanical gait characteristics at baseline are associated with progression to total knee arthroplasty.

OBJECTIVE: To determine if baseline 3-dimensional (3-D) biomechanical gait patterns differed between those patients with moderate knee osteoarthritis (OA) who progressed to total knee arthroplasty (TKA) and those that did not, and whether these differences had predictive value. METHODS: Fifty-four patients with knee OA had ground reaction forces and segment motions collected during gait. 3-D hip, knee, and ankle angles and moments were calculated over the gait cycle. Amplitude and temporal waveform characteristics were determined using principal component analysis. At followup 5-8 years later, 26 patients reported undergoing TKA. Unpaired t-tests were performed on baseline demographic and waveform characteristics between TKA and no-TKA groups. Receiver operating curve analysis, stepwise discriminate analysis, and logistic regression analysis determined the combination of features that best classified TKA and no-TKA groups and their predictive ability. RESULTS: Baseline demographic, symptomatic, and radiographic variables were similar, but 7 gait variables differed (P < 0.05) between groups. A multivariate model including overall knee adduction moment magnitude, knee flexion/extension moment difference, and stance-dorsiflexion moment had a 74% correct classification rate, with no overtraining based on cross-validation. A 1-unit increase in model score increased by 6-fold the odds of progression to TKA. CONCLUSION: In addition to the link between higher overall knee adduction magnitude and future TKA, an outcome of clear clinical importance, novel findings include altered sagittal plane moment patterns indicative of reduced ability to unload the joint during midstance. This combination of dynamic biomechanical factors had a 6-fold increased odds of future TKA; adding baseline demographic and clinical factors did not improve the model.

Bilirubin as an antioxidant: kinetic studies of the reaction of bilirubin with peroxyl radicals in solution, micelles, and lipid bilayers.

Bilirubin (BR) showed very weak antioxidant activity in a nonpolar medium of styrene or cumene in chlorobenzene. In contrast, BR exhibited strong antioxidant activity in polar media such as aqueous lipid bilayers or SDS micelles/methyl linoleate (pH 7.4), where the rate with peroxyl radicals, k(inh) = 5.0 x 10(4) M(-)(1) s(-)(1), was comparable to that with vitamin E analogues, Trolox, or PMHC. An electron-transfer mechanism accounts for the effect of the medium on the antioxidant properties of BR.