Trochanteric soft tissues have significant effects on fall-related hip fracture risk; however, little is known about their composition and spatial distribution. Accordingly, this study determined (1) the influence of sex and anatomical location on muscle thickness, adipose thickness, and total soft tissue thickness surrounding the proximal femur; and (2) the effects of sex- and location-specific soft tissue thickness on predicted fall-related hip impact forces. Ultrasound was used to measure muscle thickness, adipose thickness, and total soft tissue thickness at 12 locations surrounding the proximal femur in 25 young adult participants. Fall-related hip impact forces were predicted with a mass-spring model, accounting for force attenuation by soft tissues, at 2 common impact sites. The data demonstrated that tissue thickness and impact forces were significantly influenced by sex and anatomical location. Males had more muscle, less adipose, less total soft tissues, less force attenuation, and higher impact forces than females. Total soft tissue thickness and muscle thickness were lowest over the lateral femur, while adipose thickness was lowest over the anterolateral femur. Force attenuation was higher while impact forces were lower at the posterolateral impact site. The data support that the accuracy of hip impact models could be improved by incorporating sex-, location-, and composition-specific soft tissue thickness measures.

Clinical risk factors for hip fracture can influence both fall-induced loading and underlying femur morphology/strength; however, these effects are generally studied in isolation. We evaluated the potential effects of fall-type, biological sex, and trochanteric soft tissue thickness (TSTT) on femoral neck stresses and fracture risk index during lateral impacts. Thirty-two young adults completed voluntary falls, representative of falls in older adults. Peak impact force magnitude, direction, and point of application were extracted and applied to subject-specific beam models generated from dual-energy X-ray absorptiometry (DXA) scans. Falls with loading vectors directed more perpendicular to the femoral shaft were associated with increased compressive stress in the superior-lateral cortex (a demonstrated site of fracture initiation). Despite 44.5% greater impact force among males, no sex-based differences in femoral neck stresses were observed. Low-TSTT participants experienced greater femoral neck stresses than high-TSTT participants despite no differences in impact force magnitude. These findings highlight the importance of considering underlying differences in narrow neck mechanical properties (which vary across sex and TSTT-groups) when assessing tissue-level loading. Consistent with clinical findings, increased TSTT was associated with reduced fracture risk index among females but not males. This study provides novel insights into the mechanistic pathways through which different fall-types, biological sex, and TSTT may modulate hip fracture risk. Coupling of experimental fall simulations with tissue-level models enabled a computationally efficient method to investigate hip fracture risk, which is sensitive to biological variability.

Patients are concerned about which activities increase fracture risk and which are considered safe. Our study describes where, when, and how fractures occurred in Canadian adults followed over ten years. Falls are a leading cause of all fracture types in Canadian adults and should be prioritized in fracture prevention guidelines. Our study characterized the type and circumstances of fractures which occurred over 10 years during the Canadian Multicentre Osteoporosis Study. Details of incident fractures were recorded annually using questionnaires, and fractures were confirmed by X-ray. Medical and lifestyle history, including self-reported physical activity, was obtained by interview at baseline, year 5 and year 10. 9423 community-dwelling females and males aged ≥ 25 years were included. 1533 fractures were reported and confirmed (13

Patient lifting can expose health care workers to musculoskeletal disorder (MSD) risk factors. Portable lift assist devices may reduce exposure during lifting, however limited evidence on user feedback and efficacy is available to inform purchase decisions. Therefore, we tested the efficacy of two portable lift assist devices relative to a manual lift when lifting an individual from the floor. Participants lifted an actor from the floor using a manual technique and by using two lift assist devices, either an inflatable bladder or a mechanical device. Ratings of perceived exertion demonstrated that the lift assist devices decreased or maintained perceived exertion relative to the manual lift. Semi-structured interviews provided context where perceived benefits of the devices (i.e., decreased exertion and MSD risk) outweighed barriers (i.e., added time to call). The results of this study can inform stakeholders making decisions about lift assist devices purchases.

Towards developing more effective interventions for fall-related injuries, this study analysed a novel database from six retirement home facilities over a 4-year period comprising 1,877 fallers and 12,445 falls. Falls were characterized based on location, activity, injury site, and type, and the database was stratified across four levels of care: Independent Living, Retirement Care, Assisted Care, and Memory care. Falls most occurred within the bedroom (62.8%), and during unknown (38.1%), walking (20.2%), and transfer tasks (14.6%). Approximately one in three (37%) of all falls resulted in an injury, most commonly involving the upper limb (31.8%), head (26.3%), and lower limb (22.2%), resulting in skin tears (35.3%), aches/pains (29.1%), or bruises (28.0%). While fall location, activity, and injury site were different across levels of care, injury type was not. The data from this study can assist in targeting fall-related injury prevention strategies across levels of care within retirement facilities.

Fall-related hip fractures are a serious public health issue in older adults. As most mechanistic hip fracture risk prediction models incorporate tissue tolerance, test methods that can accurately characterize the fracture force of the femur (and factors that influence it) are imperative. While bone possesses viscoelastic properties, experimental characterization of rate-dependencies has been inconsistent in the whole-femur literature. The goal of this study was to investigate the influence of experimental paradigm on loading rate and fracture force (both means and variability) during mechanical tests simulating lateral fall loadings on the proximal femur. Six pairs of matched femurs were split randomly between two test paradigms: a 'lower rate' materials testing system (MTS) with a constant displacement rate of 60 mm/s, and a hip impact test system (HIT) comprised of a custom-built vertical drop tower utilizing an impact velocity of 4 m/s. The loading rate was 88-fold higher for the HIT (mean (SD) = 2465.49 (807.38) kN/s) compared to the MTS (27.78 (10.03) kN/s) paradigm. However, no difference in fracture force was observed between test paradigms (mean (SD) = 4096.4 (1272.6) N for HIT, and 3641.3 (1285.8) N for MTS). Within-paradigm variability was not significantly different across paradigms for either loading rate or fracture force (coefficients of variation ranging from 0.311 to 0.361). Within each test paradigm, significant positive relationships were observed between loading rate and fracture force (HIT adjusted R2 = 0.833, p = 0.007; MTS adjusted R2 = 0.983, p < 0.0001). Overall, this study provides evidence that energy-based impact simulators can be a valid method to measure femoral bone strength in the context of fall-related hip fractures. This study motivates future research to characterize potential non-linear relationships between loading rate and fracture threshold at both macro and microscales.

Introduction The use of theories, models and/or frameworks (TMFs) in implementation research and practice is essential for developing useful and testable implementation strategies. Recommendations and tools exist to aid implementation groups in selecting TMFs, but they do not explicitly outline a systematic method for identifying and selecting TMFs. This paper aimed to (1) propose a systematic consensus-based method to select TMFs to support implementation processes, and to (2) demonstrate the use of this novel method in the context of researching the implementation of hip protectors for fracture prevention in long-term care (LTC). Materials & methods We developed a systematic, consensus-based method for selecting TMFs, referred to as the Implementation Theory Selection Model (ITSM). The ITSM comprises five steps: (1) identify potentially relevant TMFs; (2) narrow the pool of TMFs; (3) appraise the relevance of eligible TMFs; (4) prioritize a short-list of TMFs for further, in-depth consideration; and (5) select TMFs through consensus with investigators and research user partners. We operationalized each step of the ITSM through a project investigating determinants of hip protector use and organizational readiness for implementation in a LTC organization in Ontario, Canada. Results Using the ITSM in our case example, we identified 66 TMFs (Step 1). Of these, 23 met our eligibility criteria (Step 2) and were appraised twice, by five appraisers (Step 3). Six TMFs (Step 4) advanced to the consensus meeting, which was attended by nine investigators and three research users, including two organizational partners and one older adult. Three rounds of voting yielded a tie between the TMFs the group felt would be most appropriate. Research users from our partner LTC organization made the final selection preferring the combination of the Practical, Robust Implementation and Sustainability Model and Consolidated Framework for Implementation Research (Step 5). Conclusions The ITSM offers a step-by-step guide for implementation groups to adopt a rigorous, transparent and reproducible method for TMF selection. Although we have demonstrated the feasibility of operationalizing each step of the ITSM in our case example, continued research is needed to evaluate and refine the ITSM to ensure it is appropriate for a wide variety of implementation contexts.

Successful implementation of fall-related injury prevention interventions such as safety flooring (SF) requires considering stakeholder feedback. This study investigated user perceptions of a SF product during initial prototype trialing and after implementation within an older adult retirement facility. Sixty participants observed the SF installed in a laboratory (Phase 1) or retirement suite (Phase 2) setting and completed a user experience questionnaire that gathered ratings and comments related to the SF’s effects on residents, employees, and novelty/attractiveness. The SF was positively perceived in both settings and participants supported SF as a valuable intervention that may mitigate fall injury severity, fear of falls, and fall-related disabilities, and improve quality of life. However, participants were uncertain about the SF’s potential effectiveness compared to other injury prevention strategies. Potential challenges included balance issues due to the ramped transitions at the suite entrances and increased acoustic levels on the SF. Participants indicated the disadvantages were limited in comparison to the potential for fall-related injury reduction. This study used a novel and iterative evaluation and engagement process as part of an intervention/implementation process. The findings reaffirm previous outcomes related to SF, while presenting some potential design and implementation issues that may assist in future intervention efforts.

Objectives Comprehensive characterization of soft tissue composition and distribution over the lateral proximal femur is necessary to improve our understanding of fall-related hip fractures; however, a protocol that produces reliable data is needed. Accordingly, the aim of this study was to assess the intra-rater reliability of B-mode ultrasound measured muscle, adipose, and total soft tissue thicknesses over the lateral proximal femur in a simulated sideways fall configuration. Methods Twenty-five young adults (12 males, 13 females, age (SD) = 20.8 (1.9) years) underwent B-mode ultrasound imaging of 12 locations over their lateral proximal femur while in a side-lying position. Side-lying was chosen to allow imaging of the tissues impacted during a lateral fall event. Muscle, adipose, and total soft tissue thicknesses were measured at each location (further grouped into posterolateral, lateral, and anterolateral locations for statistical analysis) and two-way mixed model absolute agreement intraclass correlation coefficients (ICCs) and standard error of measurement were used to assess reliability of tissue type, location, and sex. Results ICCs were excellent (ICC > 0.9) for each tissue type, measurement location, and sex. There were interactions between tissue type, measurement location, and sex on reliability. While measures of adipose thickness were excellent across all conditions, reliability of muscle and total soft tissue thickness measurements were dependent on measurement location and sex. Conclusions This ultrasound imaging protocol demonstrated good-to-excellent reliability of soft tissue-specific thickness measurements over the lateral proximal femur. This protocol has implications for subject-specific hip fracture risk screening tools and biomechanical models of impact dynamics that incorporate biofidelic soft tissue morphology.

Hip fractures are a severe health concern among older adults. While anthropometric factors have been shown to influence hip fracture risk, the low fidelity of common body composition metrics (e.g. body mass index) reduces our ability to infer underlying mechanisms. While simulation approaches can be used to explore how body composition influences impact dynamics, there is value in experimental data with human volunteers to support the advancement of computational modeling efforts. Accordingly, the goal of this study was to use a novel combination of subject-specific clinical imaging and laboratory-based impact paradigms to assess potential relationships between high-fidelity body composition and impact dynamics metrics (including load magnitude and distribution and pelvis deflection) during sideways falls on the hip in human volunteers. Nineteen females (<35 years) participated. Body composition was assessed via DXA and ultrasound. Participants underwent low-energy (but clinically relevant) sideways falls on the hip during which impact kinetics (total peak force, contract area, peak pressure) and pelvis deformation were measured. Pearson correlations assessed potential relationships between body composition and impact characteristics. Peak force was more strongly correlated with total mass (r = 0.712) and lean mass indices (r = 0.510-0.713) than fat mass indices (r = 0.401-0.592). Peak deflection was positively correlated with indices of adiposity (all r > 0.7), but not of lean mass. Contact area and peak pressure were positively and negatively associated, respectively, with indices of adiposity (all r > 0.49). Trochanteric soft tissue thickness predicted 59 % of the variance in both variables, and was the single strongest correlate with peak pressure. In five-of-eight comparisons, hip-local (vs. whole body) anthropometrics were more highly associated with impact dynamics. In summary, fall-related impact dynamics were strongly associated with body composition, providing support for subject-specific lateral pelvis load prediction models that incorporate soft tissue characteristics. Integrating soft and skeletal tissue properties may have important implications for improving the biomechanical effectiveness of engineering-based protective products.

Abstract Background This study investigated relative contributions of ankle flexor torque, muscle size, and density on balance and falls. Methods Men and women ≥50 years of age completed a peripheral quantitative computed tomography scan of the mid‐leg to quantify muscle density (MD) and cross‐sectional area; Biodex dynamometry to evaluate maximal isometric ankle flexor torque; and a single‐leg balance test on a force platform with/without eyes closed and cognitive task. Ankle flexor torque, muscle size, and density individually, together, or as interactions were examined for associations with balance (mean step duration, steps/trial) in general linear models, or with falls in Poisson regression, adjusting for age, sex, BMI, glucocorticoid use, osteoarthritis, and physical activity. Visuo‐cognitive conditions were compared. Results Among 105 participants (age: 63.3 ± 9.9 years, BMI: 25.8 ± 5.4 kg/m2, 77.1% female), 41.8% experienced ≥1 fall in the last year. Balance on one leg was dependent on ankle flexor torque when eyes were open (r = −0.220 to −0.284) and on having leaner mid‐leg muscles when eyes were closed (r = −0.123 to −0.142); cognitive challenge blunted these correlations. Individuals with leaner muscles tended to rely more on plantarflexors than dorsiflexors. A 2% lower step‐free fraction in the eyes‐closed paradigm associated with having 1 additional fall [−0.701(−1.235, −0.167)], but neither torque, muscle density, nor size related to number of falls. Conclusions Among ambulatory adults, ankle flexor torque and muscle density showed an interactive influence on balance that depended on visuo‐cognitive input. The complementary roles of torque and muscle density on balance suggest redundancy is important under dual‐tasking conditions.

Background: Reducing fall-related injuries is difficult due to the multi-factorial nature of falls, and challenges in implementing injury-preventative strategies. While safety floors are effective at absorbing energy and reducing fall-related impact forces, the low stiffness component of these floors may impair an individual's balance and mobility, thereby increasing fall risk. Research question: Therefore, the objective of this study was to investigate the influence of compliant flooring (i.e., safety flooring) on balance and mobility in young and older adults. Methods: Kinematics were measured with inertial measurement units from 20 young and 10 older adults. Static balance was evaluated during quiet stance on three flooring surfaces (traditional, safety, foam) with three stance positions (regular, tandem, one-legged). Mobility was evaluated using the 3 m timed-up-and-go test on two flooring surfaces (traditional, safety). Results: All participants were able to complete quiet standing trials on normal and safety flooring surfaces; however, most older adults could not complete one-legged stance trials or standing on foam. Significant age-related effects were observed for several balance and mobility tasks, particularly during the more challenging tandem stance condition, and the dynamic timed-up-and-go mobility test. In contrast, the introduction of safety flooring (compared to traditional flooring) had limited effects on balance/ mobility (1 of 16 outcome variables showed negative effects). Significance: Overall, the findings demonstrate minimal effects of a novel safety floor compared to the age-related differences, and provide insights to assist researchers, consumers, and industry stakeholders in the development of environments that support safe movement and maintained independence for older adults.

Purpose of Review This review surveys recent literature related to cortical bone fracture mechanics and its application towards understanding bone fragility and hip fractures. Recent Findings Current clinical tools for hip fracture risk assessment have been shown to be insensitive in some cases of elevated fracture risk leading to the question of what other factors account for fracture risk. The emergence of cortical bone fracture mechanics has thrown light on other factors at the tissue level that are important to bone fracture resistance and therefore assessment of fracture risk. Recent cortical bone fracture toughness studies have shown contributions from the microstructure and composition towards cortical bone fracture resistance. A key component currently overlooked in the clinical evaluation of fracture risk is the importance of the organic phase and water to irreversible deformation mechanisms that enhance the fracture resistance of cortical bone. Despite recent findings, there is an incomplete understanding of which mechanisms lead to the diminished contribution of the organic phase and water to the fracture toughness in aging and bone-degrading diseases. Notably, studies of the fracture resistance of cortical bone from the hip (specifically the femoral neck) are few, and those that exist are mostly consistent with studies of bone tissue from the femoral diaphysis. Summary Cortical bone fracture mechanics highlights that there are multiple determinants of bone quality and therefore fracture risk and its assessment. There is still much more to learn concerning the tissue-level mechanisms of bone fragility. An improved understanding of these mechanisms will allow for the development of better diagnostic tools and therapeutic measures for bone fragility and fracture.

Soft tissues overlying the hip play a critical role in protecting against fractures during fall-related hip impacts. Consequently, the development of an efficient and cost-effective method for estimating hip soft tissue thicknesses in living people may prove to be valuable for assessing an individual's injury risk and need to adopt preventative measures. The present study used multiple linear stepwise regression to generate prediction equations from participant characteristics (i.e., height, sex) and anthropometric measurements of the pelvis, trunk, and thigh to estimate soft tissue thickness at the iliac crests (IC) and greater trochanters (GT) in younger (16-35 years of age: 37 males, 37 females) and older (36-65 years of age: 38 males, 38 females) adults. Equations were validated against soft tissue thicknesses measured from full body Dual-energy X-ray Absorptiometry scans of independent samples (younger: 13 males, 13 females; older: 13 males, 12 females). Younger adult prediction equations exhibited adjusted R2 values ranging from 0.704 to 0.791, with more explained variance for soft tissue thicknesses at the GT than the IC; corresponding values for the older adult equations were higher overall and ranged from 0.819 to 0.852. Predicted and actual soft tissue thicknesses were significantly correlated for both the younger (R2 = 0.466 to 0.738) and older (R2 = 0.842 to 0.848) adults, averaging ≤ 0.75cm of error. This research demonstrates that soft tissue thicknesses overlying the GT and IC can be accurately predicted from equations using anthropometric measurements. These equations can be used by clinicians to identify individuals at higher risk of hip fractures who may benefit from the use of preventative measures.

Occupations or activities where donning head-supported mass (HSM) is commonplace put operators at an elevated risk of chronic neck pain. Yet, there is no consensus about what features of HSM influence the relative contributions to neck loads. Therefore, we tested four hypotheses that could increase neck loads: (i) HSM increases gravitational moments; (ii) more muscle activation is required to stabilize the head with HSM; (iii) the position of the HSM centre of mass (COM) induces gravitational moments; and (iv) the added moment of inertia (MOI) from HSM increases neck loads during head repositioning tasks. We performed a sensitivity analysis on the C5-C6 compression evaluated from a 24-degree freedom cervical spine model in OpenSim for static and dynamic movement trials. For static trials, we varied the magnitude of HSM, the position of its COM, and developed a novel stability constraint for static optimization. In dynamic trials, we varied HSM and the three principle MOIs. HSM magnitude and compression were linearly related to one another for both static and dynamic trials, with amplification factors varying between 1.9 and 3.9. Similar relationships were found for the COM position, although the relationship between C5-C6 peak compression and MOI in dynamic trials was generally nonlinear. This sensitivity analysis uncovered evidence in favour of hypotheses (i), (ii) and (iii). However, the model's prediction of C5-C6 compression was not overly sensitive to the magnitude of MOI. Therefore, the HSM mass properties may be more influential on neck compression than MOI properties, even during dynamic tasks.

Background Shock-absorbing flooring may minimise impact forces incurred from falls to reduce fall-related injuries; however, synthesized evidence is required to inform decision-making in hospitals and care homes. Methods This is a Health Technology Assessment mixed methods systematic review of flooring interventions targeting older adults and staff in care settings. Our search incorporated the findings from a previous scoping review, MEDLINE, AgeLine, and Scopus (to September 2019) and other sources. Two independent reviewers selected, assessed, and extracted data from studies. We assessed risk of bias using Cochrane and Joanna Briggs Institute tools, undertook meta-analyses, and meta-aggregation. Results 20 of 22 included studies assessed our outcomes (3 Randomised Controlled Trials (RCTs); 7 observational; 5 qualitative; 5 economic), on novel floors ( N = 12), sports floors ( N = 5), carpet ( N = 5), and wooden sub-floors (N = 1). Quantitative data related to 11,857 patient falls (9 studies), and 163 staff injuries (1 study). One care home-based RCT found a novel underlay produced similar injurious falls rates (high-quality evidence) and falls rates (moderate-quality evidence) to a plywood underlay with vinyl overlay and concrete sub-floors. Very low-quality evidence suggested that shock-absorbing flooring may reduce injuries in hospitals (Rate Ratio 0.55, 95% CI 0.36 to 0.84, 2 studies; 27.1% vs. 42.4%; Risk Ratio (RR) = 0.64, 95% CI 0.44 to 0.93, 2 studies) and care homes (26.4% vs. 33.0%; RR 0.80, 95% CI 0.70 to 0.91, 3 studies), without increasing falls. Economic evidence indicated that if injuries are fewer and falls not increased, then shock-absorbing flooring would be a dominant strategy. Fracture outcomes were imprecise; however, hip fractures reduced from 30 in 1000 falls on concrete to 18 in 1000 falls on wooden sub-floors (OR 0.59, 95% CI 0.45 to 0.78; one study; very low-quality evidence). Staff found moving wheeled equipment harder on shock-absorbing floors leading to workplace adaptations. Very low-quality evidence suggests staff injuries were no less frequent on rigid floors. Conclusion Evidence favouring shock-absorbing flooring is uncertain and of very low quality. Robust research following a core outcome set is required, with attention to wider staff workplace implications. Trial registration PROSPERO CRD42019118834 .

Low back pain (LBP) is frequently reported following rear impact collisions. Knowledge of how the facet joint capsule (FJC) mechanically behaves before and after rear impact collisions may help explain LBP development despite negative radiographic evidence of gross tissue failure. This study quantified the Green strain tensor in the facet joint capsule during rotation and translation range-of-motion tests completed before and following an in vitro simulation of a rear impact collision. Eight FSUs (4 C3-C4, 4 C5-C6) were tested. Following a preload test, FSUs were flexed and extended at 0.5 deg/s until an +/- 8 N.m moment was achieved. Anterior and posterior joint translation was then applied at 0.2 mm/s until a target +/- 400 N shear load was imposed. Markers were drawn on the facet capsule surface and their coordinates were tracked during pre- and postimpact range-of-motion tests. Strain was defined as the change in point configuration relative to the determined neutral joint posture. There were no significant differences (p > 0.05) observed in all calculated FJC strain components in rotation and translation before and after the simulated impact. Our results suggest that LBP development resulting from the initiation of strain-induced mechanoreceptors and nociceptors with the facet joint capsule is unlikely following a severe rear impact collision within the boundaries of physiological joint motion.

Metrics of femur geometry and body composition have been linked to clinical hip fracture risk. Mechanistic explanations for these relationships have generally focused on femur strength; however, impact loading also modulates fracture risk. We evaluated the potential effects of femur geometry and body composition on femoral neck stresses during lateral impacts. Fifteen female volunteers completed low-energy sideways falls on to the hip. Additionally, participants completed ultrasound and dual-energy x-ray absorptiometry imaging to characterize trochanteric soft tissue thickness (TSTT) over the hip and six metrics of femur geometry, respectively. Subject-specific beam models were developed and utilized to calculate peak femoral neck stress (σNeck), utilizing experimental impact dynamics. Except for femoral neck axis length, all metrics of femur geometry were positively correlated with σNeck (all p < 0.05). Larger/more prominent proximal femurs were associated with increased force over the proximal femur, whereas a wider neck-shaft angle was associated with greater stress generation independent of force (all p < 0.05). Body mass index (BMI) and TSTT were negatively correlated with σNeck (both p < 0.05). Despite strong correlations, these metrics of body composition appear to influence femoral neck stresses through different mechanisms. Increased TSTT was associated with reduced force over the proximal femur, whereas increased BMI was associated with greater resistance to stress generation (both p < 0.05). This study provided novel insights into the mechanistic pathways through which femur geometry and body composition may modulate hip fracture risk. Our findings complement clinical findings and provide one possible explanation for incongruities in the clinical fracture risk and femur strength literature.

Background: Muscle capacity utilization reflects the percentage of maximal knee extensor strength required to complete physical activities. Research question: Is pain associated with muscle capacity utilization during walking in older adults with knee osteoarthritis? Secondarily, is muscle capacity utilization in older adults with knee osteoarthritis sex-specific? Methods: Twenty-three participants (15 females) with symptomatic knee OA completed this study [age 67 ( +/- 8) years, body mass index 29.7 ( +/- 3.9) kg/m2, gait speed during the Six Minute Walk test 1.25 ( +/- 0.25) m/s]. Pain was measured using the Knee injury and Osteoarthritis Outcome Score. Muscle capacity utilization was quantified as the peak external knee flexor moment during level walking normalized to knee extensor maximum voluntary isometric contraction. The knee flexor moment was calculated from kinematic and kinetic data during barefoot level walking at a self-selected speed and at 1.1 m/s. Knee extensor maximum voluntary isometric contraction was measured on a dynamometer. Multiple linear regressions were used to determine the relationship between pain and muscle capacity utilization after adjusting for age, sex, body mass index, and gait speed. Independent sample t-tests examined sex differences. Results: Pain was not associated with muscle capacity utilization during self-selected and standardized walking speeds (p = 0.38 and p = 0.36, respectively). Females did not require a greater muscle capacity utilization than males to complete gait at self-selected and standardized speeds (p = 0.28, and p = 0.40, respectively). Significance: Muscle capacity utilization was not associated with pain during walking in people with knee osteoarthritis. Future work should explore more challenging activities of daily living in knee OA.

Hip fractures in older adults, which often lead to lasting impairments and an increased risk of mortality, are a major public health concern. Hip fracture risk is multi-factorial, affected by the risk of falling, the load acting on the femur, and the load the femur can withstand. This study investigates the influence of impact direction on hip fracture risk and hip protector efficacy. We simulated falls for 4 subjects, in 7 different impact directions (15° and 30° anterior, lateral, and 15°, 30°, 60°, and 90° posterior) at two different impact velocities (2.1 and 3.1 m/s), all with and without hip protector, using previously validated biofidelic finite element models. We found the highest number of fractures and highest fragility ratios in lateral and 15° posterior impacts. The hip protector attenuated femur forces by 23–49 % for slim subjects under impact directions that resulted in fractures (30° anterior to 30° posterior). The hip protector prevented all fractures (6/6) for 2.1 m/s impacts, but only 10% of fractures for 3.1 m/s impacts. Our results provide evidence that, regarding hip fracture risk, posterior-lateral impacts are as dangerous as lateral impacts, and they support the efficacy of soft-shell hip protectors for anterior- and posterior-lateral impacts.