An Accelerometer as an Alternative to a Force Plate for the Step-Up-and-Over Test.

The step-up-and-over test has been used successfully to examine knee function after knee injury. Knee function is quantified using the following variables extracted from force plate data: the maximal force exerted during the lift, the maximal impact force at landing, and the total time to complete the step. For various reasons, including space and cost, it is unlikely that all clinicians will have access to a force plate. The purpose of the study was to determine if the step-up-and-over test could be simplified by using an accelerometer. The step-up-and-over test was performed by 17 healthy young adults while being measured with both a force plate and a 3-axis accelerometer mounted at the low back. Results showed that the accelerometer and force plate measures were strongly correlated for all 3 variables (r = .90-.98, Ps < .001) and that the accelerometer values for the lift and impact indices were 6-7% higher (Ps < .01) and occurred 0.07-0.1 s later than the force plate (Ps < .05). The accelerometer returned values highly correlated to those from a force plate. Compared with a force plate, a wireless, 3-axis accelerometer is a less expensive and more portable system with which to measure the step-up-and-over test.

Effectiveness of and preference for a picture-based home office ergonomics assessment compared to a traditional in-person office ergonomics assessment: A case study from a Canadian University during the COVID-19 pandemic.

During the COVID-19 pandemic, telework best practices decreased in importance compared to the need for social distancing. It is important that ergonomics assessments for home office workstations are equally as effective as assessment for traditional offices to maintain teleworker wellbeing. The purpose of this case study is to compare a remote, picture-based, home office assessment to a traditional, in-person, office assessment for employees of one Canadian University. Intraclass Correlation Coefficients (ICCs) and Bland-Altman Analyses (BAAs) revealed that the two methods provide repeatable results, with good agreement. Feedback from the participants suggested that picture-based assessments were as effective as in-person assessments; but that picture-based assessments could be improved with video conferencing to discuss findings and ask follow-up questions. Participants found value in remote assessments and, while they preferred in-person assessments, picture-based assessments are suitable when needed as they allow for many assessments to be completed without violating social distancing restrictions.

The effect of training and workstation adjustability on teleworker discomfort during the COVID-19 pandemic.

Technological advancements have increased occupational flexibility for employees and employers alike. However, while effective telework requires planning, the COVID-19 pandemic required many employees to quickly shift to working from home without ensuring that the requirements for telework were in place. This study evaluated the transition to telework on university faculty and staff and investigated the effect of one's telework setup and ergonomics training on work-related discomfort in the at-home environment. Fifty-one percent of respondents reported increases in their existing discomfort while 24% reported new discomfort since working from home. These results suggest a need for ergonomic interventions including ergonomic training and individual ergonomic assessments for those who work from home.

Reliability of lower limb alignment measures using an established landmark-based method with a customized computer software program.

The objective of the study was to evaluate the reliability of frontal plane lower limb alignment measures using a landmark-based method by (1) comparing inter- and intra-reader reliability between measurements of alignment obtained manually with those using a computer program, and (2) determining inter- and intra-reader reliability of computer-assisted alignment measures from full-limb radiographs. An established method for measuring alignment was used, involving selection of 10 femoral and tibial bone landmarks. (1) To compare manual and computer methods, we used digital images and matching paper copies of five alignment patterns simulating healthy and malaligned limbs drawn using AutoCAD. Seven readers were trained in each system. Paper copies were measured manually and repeat measurements were performed daily for 3 days, followed by a similar routine with the digital images using the computer. (2) To examine the reliability of computer-assisted measures from full-limb radiographs, 100 images (200 limbs) were selected as a random sample from 1,500 full-limb digital radiographs which were part of the Multicenter Osteoarthritis Study. Three trained readers used the software program to measure alignment twice from the batch of 100 images, with two or more weeks between batch handling. Manual and computer measures of alignment showed excellent agreement (intraclass correlations [ICCs] 0.977-0.999 for computer analysis; 0.820-0.995 for manual measures). The computer program applied to full-limb radiographs produced alignment measurements with high inter- and intra-reader reliability (ICCs 0.839-0.998). In conclusion, alignment measures using a bone landmark-based approach and a computer program were highly reliable between multiple readers.

Case study: a novel biomechanical approach for evaluating extended body armor systems.

To combat the devastating effects of improvised explosive devices (IEDs), body armor that provides extended coverage has been developed. However, this extended coverage increases the armor's weight and may restrict movement. Throughout this case study, a novel technique to assess several armor systems was investigated. Four soldiers performed shoulder and trunk movements while wearing each of the six different armor inserts. Electromyography (EMG) was used to quantify muscular activity and inertial motion sensors were used to determine joint range of motion (ROM). Outcome measures included maximum ROM, integrated EMG, and the soldiers' subjective rankings. For the shoulder tasks, objective ROM and EMG measures were related to each other as well as to subjective rankings and armor material properties. Conversely, little agreement was found between measures for the trunk tasks. Results of this preliminary investigation indicate that combining shoulder ROM and EMG measures has the potential to provide an objective assessment of body armor systems.

A comparison between a new model and current models for estimating trunk segment inertial parameters.

Modeling of the body segments to estimate segment inertial parameters is required in the kinetic analysis of human motion. A new geometric model for the trunk has been developed that uses various cross-sectional shapes to estimate segment volume and adopts a non-uniform density function that is gender-specific. The goal of this study was to test the accuracy of the new model for estimating the trunk's inertial parameters by comparing it to the more current models used in biomechanical research. Trunk inertial parameters estimated from dual X-ray absorptiometry (DXA) were used as the standard. Twenty-five female and 24 male college-aged participants were recruited for the study. Comparisons of the new model to the accepted models were accomplished by determining the error between the models' trunk inertial estimates and that from DXA. Results showed that the new model was more accurate across all inertial estimates than the other models. The new model had errors within 6.0% for both genders, whereas the other models had higher average errors ranging from 10% to over 50% and were much more inconsistent between the genders. In addition, there was little consistency in the level of accuracy for the other models when estimating the different inertial parameters. These results suggest that the new model provides more accurate and consistent trunk inertial estimates than the other models for both female and male college-aged individuals. However, similar studies need to be performed using other populations, such as elderly or individuals from a distinct morphology (e.g. obese). In addition, the effect of using different models on the outcome of kinetic parameters, such as joint moments and forces needs to be assessed.

Evaluating movement performance: What you see isn't necessarily what you get.

With the goal of reducing injury and enhancing performance, movement screening tools score an individual's movements against a standard and because it is a predictor of injury symmetry is often included in the score. Movement quality screening tools only consider kinematic asymmetry, which may underestimate the degree of asymmetry present during movement. Consider joint forces: if these forces are atypical, additional stress is created and control is reduced, which can lead to injury if the asymmetry is not addressed. The purpose of this study is to investigate movement symmetry in the kinematic, kinetic and muscle activity components of movement during a parallel squat. Thirty-four healthy individuals completed five body-weight, parallel squats. A motion capture system, two portable force plates, and electromyography (EMG) sensors recorded the squat motion, ground reaction forces and muscle activity. The variables of interest were the joint angles, joint moments, and EMG waveforms. Cross-correlations and normalized root-mean-square values were calculated for the left and right ankles, knees, and hips for each variable. A repeated-measures analysis of variance (ANOVA) tested for differences in symmetry (cross-correlation and nRMS) between the kinematic, kinetic, and muscle activity components at the ankle, knee, and hip during the squat. At all joints the kinematic component had the highest degree of symmetry, and the kinetic and muscle activity components showed poorer symmetry, with the muscle activity component being the least symmetric. The differences in symmetry between movement components suggests that movement performance evaluations should not rely exclusively on kinematics and observation to identify potential movement faults.

Trunk density profile estimates from dual X-ray absorptiometry.

Accurate body segment parameters are necessary to estimate joint loads when using biomechanical models. Geometric methods can provide individualized data for these models but the accuracy of the geometric methods depends on accurate segment density estimates. The trunk, which is important in many biomechanical models, has the largest variability in density along its length. Therefore, the objectives of this study were to: (1) develop a new method for modeling trunk density profiles based on dual X-ray absorptiometry (DXA) and (2) develop a trunk density function for college-aged females and males that can be used in geometric methods. To this end, the density profiles of 25 females and 24 males were determined by combining the measurements from a photogrammetric method and DXA readings. A discrete Fourier transformation was then used to develop the density functions for each sex. The individual density and average density profiles compare well with the literature. There were distinct differences between the profiles of two of participants (one female and one male), and the average for their sex. It is believed that the variations in these two participants' density profiles were a result of the amount and distribution of fat they possessed. Further studies are needed to support this possibility. The new density functions eliminate the uniform density assumption associated with some geometric models thus providing more accurate trunk segment parameter estimates. In turn, more accurate moments and forces can be estimated for the kinetic analyses of certain human movements.

Effect of foot rotation on knee kinetics and hamstring activation in older adults with and without signs of knee osteoarthritis.

BACKGROUND: To determine the effects of changing the natural foot progression angle during gait (internal and external foot rotation) on the knee's adduction moment, lateral-medial shear force, and the ratio of medial-lateral hamstring muscle activation in those with signs of knee osteoarthritis and a matched healthy control group. METHODS: Twelve subjects with signs of knee osteoarthritis and 12 matched healthy control subjects were evaluated. A 3D gait analysis system calculated forces and moments at the knee while the subjects walked in three conditions: (1) normal foot position, (2) external foot rotation, (3) internal foot rotation. Medial and lateral hamstring EMG data was also collected simultaneously and used to calculate the medial-lateral hamstring activation ratio during the stance phase of the gait cycle. Repeated measures ANOVAs were used to compare foot rotation conditions within each group; while between group comparisons were performed in the normal rotation condition only using t-tests. FINDINGS: Those with knee osteoarthritis (OA) had an increased late stance knee adduction moment and a decreased medial-lateral hamstring activation ratio as compared to the healthy control group. Also, external foot rotation decreased the late stance knee adduction moment, lateral-medial shear force, and hamstring activation ratio. However, internal foot rotation did not increase these measures. INTERPRETATION: Changes in foot position during gait have the ability to alter both the external loading of the knee joint and hamstring muscle activation patterns during gait. This may have implication in helping to unload the knee's articular cartilage.

Mechanical factors relate to pain in knee osteoarthritis.

BACKGROUND: Pain experienced by people with knee osteoarthritis is related to psychosocial factors and damage to articular tissues and/or the pain pathway itself. Mechanical factors have been speculated to trigger this pain experience; yet mechanics have not been identified as a source of pain in this population. The purpose of this study was to identify whether mechanics could explain variance in pain intensity in people with knee osteoarthritis. METHODS: Data from 53 participants with physician-diagnosed knee osteoarthritis (mean age=68.5 years; standard deviation=8.6 years) were analyzed. Pain intensity was reported on the Western Ontario and McMaster Universities Osteoarthritis Index. Mechanical measures included weight-bearing varus-valgus alignment, body mass index and isokinetic quadriceps torque. Gait analysis captured the range of adduction-abduction angle, range of flexion-extension angle and external knee adduction moment during level walking. FINDINGS: Pain intensity was significantly related to the dynamic range of flexion-extension during gait and body mass index. A total of 29% of the variance in pain intensity was explained by mechanical variables. The range of flexion-extension explained 18% of variance in pain intensity. Body mass index added 11% to the model. The knee adduction moment was unrelated to pain intensity. INTERPRETATION: The findings support that mechanical factors are related to knee osteoarthritis pain. Because limitations in flexion-extension range of motion and body size are modifiable factors, future research could examine whether interventions targeting these mechanics would facilitate pain management.

The effect of internal and external foot rotation on the adduction moment and lateral-medial shear force at the knee during gait.

It has been hypothesised that those with medial compartment knee osteoarthritis tend to externally rotate their foot during gait in order to unload the diseased compartment. This has been found to decrease the adduction moment at the knee during late stance, although the effects of foot rotation on shear forces at the knee have not yet been determined. Also, the effects of internal foot rotation on the knee during gait are not clear. This study performed a gait analysis on 11 healthy participants (M: 6; mean age 22.9+/-1.8 years) in three conditions: (1) natural foot rotation position; (2) internal foot rotation and (3) external foot rotation. Three-dimensional gait analysis calculated the knee adduction moment and lateral-medial shear force for all three foot rotation conditions. Internal rotation of the foot increased the knee adduction moment and lateral-medial shear force magnitude during late stance, while external rotation of the foot decreased the magnitude of both these measures. This implies that walking with an externally and internally rotated foot may unload the diseased compartment for those with medial and lateral compartment knee OA, respectively. Also, the relationship of foot rotation angle to the adduction moment and lateral-medial shear force was strengthened when data were corrected for the subject's normal walking condition. Knee OA subject data revealed that they were able to reduce the knee adduction moment more than normal subjects during late stance, indicating that other factors besides the rotation of the foot need to be investigated.

Self-efficacy mediates walking performance in older adults with knee osteoarthritis.

BACKGROUND: Self-efficacy is a determinant of walking performance in older adults with knee osteoarthritis. We examined whether self-efficacy mediated the effect of age, psychosocial, impairment, and mechanical factors on walking performance. METHODS: Fifty-four participants with knee osteoarthritis completed the Six Minute Walk test and Arthritis Self-Efficacy Scale. Independent variables reflected age, psychosocial (depressive symptoms), impairment (pain, stiffness), and mechanical (strength, obesity) factors. RESULTS: Self-efficacy fully mediated the effect of age and impairments on walking. The effects of strength were only partially mediated by self-efficacy. Depressive symptoms and obesity were not mediated by self-efficacy. CONCLUSIONS: These findings are consistent with Social Cognitive Theory, according to which age may alter outcome expectations, and impairments like pain and stiffness provide negative physiological feedback to influence performance. Mechanical factors like strength and obesity may better represent a person's capabilities and interact with other variables to influence physical performance in older adults with knee osteoarthritis.

Knee biomechanics of alternate stair ambulation patterns.

PURPOSE: This study compared the kinematics and kinetics of the knee joint during traditional step-over-step (SOS) and compensatory step-by-step lead-leg (SBSL) and trail-leg (SBST) stair ambulation patterns. METHODS: Seventeen (M:9) healthy adults completed five trials of ascent and descent using three different stepping patterns: 1) SBSL, 2) SBST, and 3) SOS. Kinematics and kinetics were collected with an optoelectronic motion-tracking system and a force plate embedded into a four-step staircase. An inverse-dynamics link-segment model (QGAIT system) was used to calculate the net joint kinetics. RESULTS: During stair ascent, different peak anteroposterior (AP) forces were observed across all three stepping patterns (SOS > SBSL > SBST, P < 0.05). During ascent, the flexion moments of SOS (0.96 N x m x kg(-1)) and SBSL (0.97 N x m x kg(-1)) patterns were similar and much larger than the SBST moments (0.14 N x m x kg(-1)). In the descent conditions, the initial AP peak force for SOS was larger than that of SBSL and SBST. However, the second peak force for SOS (4.92 N x kg(-1)) and SBST (4.68 N x kg(-1)) were larger than SBSL (1.57 N x kg(-1)). During descent, the initial peak flexion moment for the SOS pattern was larger than SBSL and SBST, whereas during the second peak, SOS (1.05 N x m x kg(-1)) and SBST (1.11 N x m x kg(-)) were no different and larger than SBSL (0.18 N x m x kg(-1)). CONCLUSION: Overall, SBSL during ascent and SBST during descent had the highest loads. These results increase our understanding of alternative stepping patterns and have important clinical (reduction of loading on injured/diseased leg) and rehabilitation implications.

The influence of gait pattern on signs of knee osteoarthritis in older adults over a 5-11 year follow-up period: a case study analysis.

There is evidence that joint load is a factor in the development of osteoarthritis (OA) and, while altered gait profiles have been linked with OA, it is unknown if abnormal gait is a cause or effect of the disease. While the knee's adduction moment has been implicated in the development and progression of knee OA, it is also known that shearing forces are detrimental to the health of cartilage. The purpose of this pilot study was to examine the adduction moment and gait shear forces to determine if they may lead to signs of knee OA in older adults as they age. Knee gait kinetics, standardized radiographs and a questionnaire were collected on 28 older adults (M:13) during an initial visit, and 5 to 11 years later. Radiographic score increased (knees became more osteoarthritic in 15 of 28 subjects) over time. However, gait time-distance measures remained constant in disease free participants. Two returning participants developed symptoms and radiographic evidence of knee OA. The subject with the largest adduction moment developed signs of medial OA while the subject with the smallest adduction moment developed signs of lateral OA. In addition, there was a strong correlation between the magnitudes of the adduction moment and lateral-medial shear force that needs to be investigated further. Results suggest that gait can remain stable over time in older adults. Also, the medial and lateral OA case study findings suggest that the extreme gait profiles seen in these two participants may be important in explaining cartilage breakdown and the development of OA. This longitudinal study would suggest that perhaps it is the abnormal gait pattern that leads to the development of OA, although a much larger study would be needed to confirm this finding.

Role of knee kinematics and kinetics on performance and disability in people with medial compartment knee osteoarthritis.

BACKGROUND: Although gait characteristics have been well documented in people with knee osteoarthritis, little is known about the relationships between gait characteristics and performance or disability. Our purpose was to examine the role of knee kinematics and kinetics on walking performance and disability in people with knee osteoarthritis. We also examined whether pain mediated the relationship between the knee adduction moment and performance or disability. METHODS: Three-dimensional gait analysis was conducted on 54 people with medial compartment knee osteoarthritis. Performance was quantified with the Six Minute Walk test and disability was self-reported on the Short Form-36. The pain subscale of the Western Ontario McMaster Universities Osteoarthritis Index and the functional self-efficacy subscale of the Arthritis Self-Efficacy scale were completed. FINDINGS: A step-wise linear regression demonstrated that the variance in Six Minute Walk test scores was explained by functional self-efficacy (50%) and the range of knee motion (8%). The variance in Short Form-36 was explained by pain (36%), the peak extension angle (19%) and the range of knee motion (4%). Pain was unrelated to the knee adduction moment so analyses of pain as a mediator of the adduction moment on either performance or disability were halted. INTERPRETATION: Kinematic output from the motor control system is useful in understanding some variance in current performance and disability in people with knee osteoarthritis. The knee adduction moment was unrelated to these variables and pain did not mediate between the knee adduction moment and performance or disability. Therefore this moment does not explain current clinical status in people with knee osteoarthritis based on the measures of performance and disability used in this study.

Using an accelerometer and the step-up-and-over test to evaluate the knee function of patients with anterior cruciate ligament reconstruction.

BACKGROUND: Evaluating the dynamic knee function of patients after anterior cruciate ligament reconstruction is a challenge. A variety of objective tests have been developed but for various reasons few are regularly used in the clinic. It may be practical to perform the step-up-and-over test with an accelerometer. METHODS: A control group (N=26) and an experimental group with a reconstructed anterior cruciate ligament (N=25) completed questionnaires quantifying subjective knee function and fear of re-injury and then completed the step-up-and-over test. FINDINGS: Results showed that the experimental group performed differently than the control group for the step-up-and-over test's Lift Symmetry and Impact Symmetry (P<0.05) and performance on these measures was related to the participant's subjective knee function (ρ=-0.46, P<0.01; ρ=-0.33, P<0.05, respectively). Supplemental results for individual leg performance and the patient's fear of re-injury are also reported and discussed. INTERPRETATION: Performance on the step-up-and-over test is different for participants with anterior cruciate ligament reconstruction than for those with intact anterior cruciate ligaments, and that performance is related to one's opinion of their knee's function.

Contribution of psychosocial and mechanical variables to physical performance measures in knee osteoarthritis.

BACKGROUND AND PURPOSE: This cross-sectional study evaluated the relative contributions of psychosocial and mechanical variables to physical performance measures in people with knee osteoarthritis (OA). SUBJECTS: Fifty-four subjects (age, in years: mean=68.3, SD=8.7, range=50-87) with radiographically confirmed knee OA were included in this study. METHODS: Physical performance measures included the Six-Minute Walk Test (SMW), the Timed "Up & Go" Test (TUG), and a stair-climbing task (STR). Responses to psychosocial questionnaires that reflect depression, anxiety, and self-efficacy (a person's confidence in his or her ability to complete a task) were collected. Mechanical variables measured included body mass index and knee strength (force-generating capacity of muscle). Stepwise linear regressions were performed with the SMW, TUG, and STR as separate dependent variables. RESULTS: Functional self-efficacy explained the greatest amount of variance in all performance measures, contributing 45% or more. Knee strength and body weight also explained some variance in performance measures. Anxiety and depression did not explain any variance in performance. DISCUSSION AND CONCLUSION: Physical therapists evaluating the significance of the SMW, TUG, and STR scores in subjects with knee OA should note that a large part of each score reflects self-efficacy, or confidence, for physical tasks, with some contributions from knee strength and body weight.

The effect of sustained static kneeling on kinetic and kinematic knee joint gait parameters.

Despite epidemiological evidence for kneeling as an occupational risk factor for knee osteoarthritis, biomechanical evidence is lacking. Gait knee joint mechanics, a common measure used to study knee osteoarthritis initiation, were used in the present study to investigate the effect of sustained static kneeling on the knee. Ten healthy male subjects (24.1 years ± 3.5) performed ten baseline walking trials, followed by a 30-min kneeling protocol and a second set of walking trials. Knee joint moments and angles were calculated during the stance phase. Within-subject root mean squared differences were compared within and between the pre- and post-kneeling gait trials. Differences were observed between the pre-kneeling and post-kneeling walking trails for flexion and adduction knee moments (0.12 Nm/kg ± 0.03, 0.07 Nm/kg ± 0.02) and angles (3.18° ± 1.22 and 1.64° ± 1.15), indicating that sustained static deep-knee flexion kneeling does acutely alter knee joint gait parameters.

Knee and hip kinetics during normal stair climbing.

Understanding joint kinetics during activities of daily living furthers our understanding of the factors involved in joint pathology and the effects of treatment. In this study, we examined hip and knee joint kinetics during stair climbing in 35 young healthy subjects using a subject-specific knee model to estimate bone-on-bone tibiofemoral and patello-femoral joint contact forces. The net knee forces were below one body weight while the peak posterior-anterior contact force was close to one body weight. The peak distal-proximal contact force was on average 3 times body weight and could be as high as 6 times body weight. These contact forces occurred at a high degree of knee flexion where there is a smaller joint contact area resulting in high contact stresses. The peak knee adduction moment was 0.42 (0.15) Nm/kg while the flexion moment was 1.16 (0.24) Nm/kg. Similar peak moment values, but different curve profiles, were found for the hip. The hip and knee posterior-anterior shear forces and the knee flexion moment were higher during stair climbing than during level walking. The most striking difference between stair ascent and level walking was that the peak patello-femoral contact force was 8 times higher during stair ascent. These data can be used as baseline measures in pathology studies, as input to theoretical joint models, and as input to mechanical joint simulators.

Static and dynamic biomechanics of foot orthoses in people with medial compartment knee osteoarthritis.

OBJECTIVE: Gait biomechanics (knee adduction moment, center of pressure) and static alignment were investigated to determine the mechanical effect of foot orthoses in people with medial compartment knee osteoarthritis. DESIGN: Repeated measures design in which subjects were exposed to three conditions (normal footwear, heel wedge and orthosis) in random order. BACKGROUND: The knee adduction moment is an indirect measure of medial compartment loading. It was hypothesized that the use of a 5 degrees valgus wedge and 5 degrees valgus modified orthosis would shift the center of pressure laterally during walking, thereby decreasing the adduction moment arm and the adduction moment. METHODS: Peak knee adduction moment and center of pressure excursion were obtained in nine subjects with medial compartment knee OA during level walking using an optoelectric system and force plate. Static radiographs were taken in 12 subjects using precision radiographs. RESULTS: There was no difference between conditions in static alignment, the peak adduction moment or excursion of the center of pressure in the medial-lateral direction. No relationship was found between the adduction moment and center of pressure excursion in the medial-lateral plane. The displacement of the center of pressure in the anterior-posterior direction, measured relative to the laboratory coordinate system, was decreased with the orthosis compared to the control condition (P=0.036) and this measure was correlated with the adduction moment (r=0.45, P=0.019). CONCLUSIONS: The proposed mechanism was not supported by the findings. The reduction in the center of pressure excursion in the anterior-posterior direction suggests that foot positioning was altered, possibly to a toe-out position, while subjects wore the orthoses. Based on the current findings, we hypothesize that toe-out positioning may reduce medial joint load. RELEVANCE: Knee Osteoarthritis is the most common cause of chronic disability amongst seniors. Developing inexpensive, non-invasive treatment strategies for this large population has potential to impact health care costs, quality of life and clinical outcomes.