Exposure assessment of kneeling work activities among floor layers

Visualising knee loading patterns during kneeling and the development of a laboratory-based adaptation of the Aberdeen Weight-Bearing Test (Knee)

BACKGROUND

Information regarding the loading of key anatomical structures of the knee during kneeling would enhance existing functional tests, yet current visualisation methods are limited and require further development.

AIMS

(1) Develop a knee loading visualisation technique to investigate loading patterns of the knee during kneeling; and (2) determine the utility of the technique in combination with vertical ground reaction forces and centre of pressure data in the lab-based Aberdeen Weight-Bearing Test (Knee) by assessing their reliability.

METHODS

Fourteen healthy participants conducted kneeling tasks with and without knee pads across two testing sessions. Eight force-sensitive resistors were affixed to the right knee throughout different kneeling tasks: upright kneeling, and reaching forward, back, left, and right. A photo of the force-sensitive resistor configuration was used to generate participant-specific heat maps of knee loading. Two in-ground force platforms were used to measure vertical ground reaction forces and centre of pressure.

RESULTS

The inferior patella tendon showed the highest proportion of activation during both bare and knee pad kneeling for all kneeling tasks. Knee pads reduced the repeatability of knee loading patterns. Force-sensitive resistor activation and vertical ground reaction force components of the lab-based Aberdeen Weight-Bearing Test (Knee) were shown to be reliable, whereas the centre of pressure data was unreliable.

CONCLUSION

We have developed a lab-based technique for visualising knee loading using force-sensitive resistors. The combination of force-sensitive resistor activation and vertical ground reaction force data provides valuable insights into both the magnitude and locations of applied loads throughout kneeling.

Quantifying high flexion postures in occupational childcare as they relate to the potential for increased risk of knee osteoarthritis

High knee flexion postures, despite their association with increased incidences of osteoarthritis, are frequently adopted in occupational childcare. This study sought to define and quantify high flexion postures typically adopted in childcare to evaluate any increased likelihood of knee osteoarthritis development. Through video analysis of eighteen childcare workers caring for infant, toddler, and preschool-aged children, eight high knee flexion postures were identified and quantified by duration and frequency. An analysis of postural adoption by task was subsequently performed to determine which might pose the greatest risk for cumulative joint trauma. Childcare workers caring for children of all ages were found to adopt kneeling and seated postures for extended durations and at elevated frequencies, exceeding proposed thresholds for incidences of knee osteoarthritis development. Structured activities, playing, and feeding tasks demanded the greatest adoption of high flexion postures and should be evaluated to minimise the potential childcare-related risks of osteoarthritis. Practitioner summary: High knee flexion postures (kneeling, squatting, etc.) have been associated with increased incidences of knee injury yet are commonly adopted in childcare. Childcare workers' postures were examined through video analysis revealing that proposed adoption thresholds for knee health are commonly exceeded when caring for children of all ages. Abbreviations: OA: osteoarthritis; WSIB: workplace safety insurance board; CAD: Canadian Dollar; DK: dorsiflexed kneeling; PK: plantarflexed kneeling; SAK: single arm supported kneeling; DAK: double arm supported kneeling; FS: flatfoot squatting; HS: heels up squatting; FLRS: floor sitting; SS: side sitting or leaning; STLS: stool sitting; BR: bending and reaching.

Occupational Risk in Knee Osteoarthritis: A Systematic Review and Meta-Analysis of Observational Studies

OBJECTIVE

To assess the association between occupational exposures and knee osteoarthritis (OA).

METHODS

We systematically searched for observational studies that examined the relationship between occupational exposures and knee OA and total knee replacement. Four databases were searched up to October 1, 2019. Two reviewers independently assessed study quality using the Newcastle-Ottawa Scale and evidence quality using the Grading of Recommendations Assessment, Development and Evaluation approach. Subgroup meta-analyses were conducted for important study characteristics and each type of occupational exposure. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were estimated for the meta-analysis using random-effects models.

RESULTS

Eighty eligible studies were identified including 25 case-control (n = 20,505 total participants), 36 cross-sectional (n = 139,463 total participants), and 19 cohort studies (n = 16,824,492 total participants). A synthesis of 71 studies suggested increased odds of knee OA (OR 1.52 [95% CI 1.37-1.69]) by combining different physically demanding jobs and occupational activities as compared to sedentary occupations and/or low-exposure groups. Odds of knee OA were greater in males and in industry-based studies and studies assessing lifetime occupational exposures. There were 9 specific job titles that were associated with knee OA, including farmer, builder, metal worker, and floor layer. Occupational lifting, kneeling, climbing, squatting, and standing were all associated with higher odds of knee OA as compared to the odds of knee OA in sedentary workers.

CONCLUSION

Strenuous, physically demanding occupations and occupational activities were associated with increased odds of knee OA as supported by moderate-quality evidence. Specifically, agricultural and construction sectors, which typically involve heavy lifting, frequent climbing, prolonged kneeling, squatting, and standing, carried increased odds of knee OA.

Kneeling trunk kinematics during simulated sloped roof shingle installation

Trunk musculoskeletal disorders are common among residential roofers. Addressing this problem requires a better understanding of the movements required to complete working tasks, such as affixing shingles on a sloped residential roof. We analyzed the extent to which the trunk kinematics during a shingling process are altered due to different angles of roof slope. Eight male subjects completed a kneeling shingle installation process on three differently sloped roof surfaces. The magnitude of the trunk kinematics was significantly influenced by both slope and task phase of the shingling process, depending on the metric. The results unequivocally point to roof slope and task phase as significant factors altering trunk kinematics. However, extension of the results to roofing workers should be done carefully, depending on the degree to which the study protocol represents the natural setting. Future studies on shingle installation in residential roofing should absolutely consider capturing a wider array of shingling procedures in order to encapsulate all the possible methods that are used due to the lack of a standardized procedure.

Are knee savers and knee pads a viable intervention to reduce lower extremity musculoskeletal disorder risk in residential roofers?

One factor commonly associated with musculoskeletal disorder risk is extreme postures. To lessen this risk, individuals must be in an as neutral posture as possible while working. We analyzed how the inclusion of different combinations of two interventions-knee pads and knee savers-can alter lower extremity kinematics during deep or near full flexion kneeling occurs while on different sloped surfaces. Nine male subjects were requested to keep a typical resting posture while kneeling on sloped roofing simulator. We observed that the introduction of a wearable third party device considerably altered lower extremity full flexion kneeling kinematics compared to level deep kneeling. This study provided a sound base for the use of third party devices to reduce musculoskeletal disorder risk on a sloped surface, however further testing with other musculoskeletal disorder risk factors is needed prior to conclusive recommendation.

The effects of a simulated occupational kneeling exposure on squat mechanics and knee joint load during gait

Occupational kneeling is associated with an increased risk for tibiofemoral knee osteoarthritis. Forces on the knee in the kneeling posture, as well as the greater incidence of meniscus tears among workers, likely contribute to the increased risk. We hypothesise that an additional mechanism may contribute - altered neuromuscular control due to prolonged high knee flexion. Forty participants (20 male, 20 female) completed an evaluation of gait and squatting before, immediately following, and 30 min following a 30 min simulated occupational kneeling exposure. An increase in the peak external knee adduction moment and a delay in vastus medialis activation onset during walking were observed post-kneeling, as well as increased frontal plane knee motion during squatting. This was the first investigation to find changes in high flexion transitions as a result of kneeling. Greater frontal plane knee motion may increase the risk for meniscal tears, and subsequently, knee osteoarthritis. Practitioner Summary: A 30 min simulated occupational kneeling exposure resulted in small but significant gait changes. The greatest effect was on frontal plane knee movement during squatting, which is especially relevant to occupations requiring frequent kneeling/squatting. This increased motion may indicate an increased risk of injury, which supports a link to knee osteoarthritis.

Knee joint moments during high flexion movements: Timing of peak moments and the effect of safety footwear

AIM

(1) Characterize knee joint moments and peak knee flexion moment timing during kneeling transitions, with the intent of identifying high-risk postures. (2) Determine whether safety footwear worn by kneeling workers (construction workers, tile setters, masons, roofers) alters high flexion kneeling mechanics.

METHODS

Fifteen males performed high flexion kneeling transitions. Kinetics and kinematics were analyzed for differences in ascent and descent in the lead and trail legs.

RESULTS

Mean±standard deviation peak external knee adduction and flexion moments during transitions ranged from 1.01±0.31 to 2.04±0.66% body weight times height (BW∗Ht) and from 3.33 to 12.6% BW∗Ht respectively. The lead leg experienced significantly higher adduction moments compared to the trail leg during descent, when work boots were worn (interaction, p=0.005). There was a main effect of leg (higher lead vs. trail) on the internal rotation moment in both descent (p=0.0119) and ascent (p=0.0129) phases.

CONCLUSION

Peak external knee adduction moments during transitions did not exceed those exhibited during level walking, thus increased knee adduction moment magnitude is likely not a main factor in the development of knee OA in occupational kneelers. Additionally, work boots only significantly increased the adduction moment in the lead leg during descent. In cases where one knee is painful, diseased, or injured, the unaffected knee should be used as the lead leg during asymmetric bilateral kneeling. Peak flexion moments occurred at flexion angles above the maximum flexion angle exhibited during walking (approximately 60°), supporting the theory that the loading of atypical surfaces may aid disease development or progression.

Evaluation of knee joint forces during kneeling work with different kneepads

The main purpose of this study is to determine knee joint forces resulting from kneeling work with and without kneepads to quantify how different kneepads redistribute force. Eleven healthy males simulated a tile setting task to different locations during six kneepad states (five different kneepad types and without kneepad). Peak and average forces on the anatomical landmarks of both knees were obtained by custom force sensors. The results revealed that kneepad design can significantly modify the forces on the knee joint through redistribution. The Professional Gel design was preferred among the five tested kneepads which was confirmed with both force measurements and participants' responses. The extreme reaching locations induced significantly higher joint forces on left knee or right knee depending on task. The conclusion of this study is that a properly selected kneepad for specific tasks and a more neutral working posture can modify the force distribution on the knees and likely decrease the risk of knee disorders from kneeling work.

Stand up: comparison of two electrical screed levelling machines to reduce the work demands for the knees and low back among floor layers

Electrical screed levelling machines are developed to reduce kneeling and trunk flexion of sand-cement-bound screed floor layers. An observational intervention study among 10 floor layers was performed to assess the differences between a self-propelled and a manually moved machine. The outcome measures were work demands, production time, perceived load, discomfort and applicability. Compared to the self-propelled machine, the duration of kneeling (∆13 min; p = 0.003) and trunk flexion (∆12 min; p < 0.001) was shorter using the manually moved machine, and the duration of pushing and pulling increased (∆39 min; p < 0.001). No significant or relevant differences were found for production time, perceived load and discomfort. Nine out of ten floor layers found the manually moved machine applicable and three out of ten found the self-propelled machine applicable. When compared with the traditional manner of floor laying, both electrical machines reduced the exposure towards kneeling and trunk flexion. Practitioner Summary: Electrical machines may help to reduce high physical work demands on floor layers. A manually moved machine is better applicable for the installation of screed floors in residences with smaller floor areas. A self-propelled machine is better applicable on large floor areas with a minimum width of 4 m.

Mechanical stress

This chapter discusses mechanical stressors that are believed to be associated with work-related musculoskeletal disorders. It starts with an introduction to work-related musculoskeletal disorders (particularly those with high incidences in workplaces, such as disorders of low back, neck/shoulder, hand/wrist, elbow, and knee) in high-risk industries, and those mechanical stressors (such as high forces, awkward postures, high repetitions, excessive contact stress, and harmful human vibrations) in workplaces that are responsible for these disorders. Quantification methods of these mechanical stressors are then discussed. Although various quantification methods such as self-report, observational technique, and direct measurement are discussed, details are focused on many of those well-published observational techniques used by practitioners to assess risk levels of these mechanical stressors in jobs. These methods can quantify job mechanical stressors and provide risk level indications that can be used by practitioners to facilitate their decision making. These methods can also be used to evaluate the improvements of ergonomics interventions by comparing the risk levels quantitatively before and after the interventions.

Exploring physical exposures and identifying high-risk work tasks within the floor layer trade

INTRODUCTION

Floor layers have high rates of musculoskeletal disorders yet few studies have examined their work exposures. This study used observational methods to describe physical exposures within floor laying tasks.

METHODS

We analyzed 45 videos from 32 floor layers using Multimedia-Video Task Analysis software to determine the time in task, forces, postures, and repetitive hand movements for installation of four common flooring materials. We used the WISHA checklists to define exposure thresholds.

RESULTS

Most workers (91%) met the caution threshold for one or more exposures. Workers showed high exposures in multiple body parts with variability in exposures across tasks and for different materials. Prolonged exposures were seen for kneeling, poor neck and low back postures, and intermittent but frequent hand grip forces.

CONCLUSIONS

Floor layers experience prolonged awkward postures and high force physical exposures in multiple body parts, which probably contribute to their high rates of musculoskeletal disorders.

An expert-based job exposure matrix for large scale epidemiologic studies of primary hip and knee osteoarthritis: the Lower Body JEM

BACKGROUND

When conducting large scale epidemiologic studies, it is a challenge to obtain quantitative exposure estimates, which do not rely on self-report where estimates may be influenced by symptoms and knowledge of disease status. In this study we developed a job exposure matrix (JEM) for use in population studies of the work-relatedness of hip and knee osteoarthritis.

METHODS

Based on all 2227 occupational titles in the Danish version of the International Standard Classification of Occupations (D-ISCO 88), we constructed 121 job groups comprising occupational titles with expected homogeneous exposure patterns in addition to a minimally exposed job group, which was not included in the JEM. The job groups were allocated the mean value of five experts' ratings of daily duration (hours/day) of standing/walking, kneeling/squatting, and whole-body vibration as well as total load lifted (kg/day), and frequency of lifting loads weighing ≥20 kg (times/day). Weighted kappa statistics were used to evaluate inter-rater agreement on rankings of the job groups for four of these exposures (whole-body vibration could not be evaluated due to few exposed job groups). Two external experts checked the face validity of the rankings of the mean values.

RESULTS

A JEM was constructed and English ISCO codes were provided where possible. The experts' ratings showed fair to moderate agreement with respect to rankings of the job groups (mean weighted kappa values between 0.36 and 0.49). The external experts agreed on 586 of the 605 rankings.

CONCLUSION

The Lower Body JEM based on experts' ratings was established. Experts agreed on rankings of the job groups, and rankings based on mean values were in accordance with the opinion of external experts.

Occupational kneeling and squatting: development and validation of an assessment method combining measurements and diaries

Objectives

As knee-straining postures such as kneeling and squatting are known to be risk factors for knee disorders, there is a need for effective exposure assessment at the workplace. Therefore, the aim of this study was to develop a method to capture knee-straining postures for entire work shifts by combining measurement techniques with the information obtained from diaries, and thus avoiding measuring entire work shifts. This approach was applied to various occupational tasks to obtain an overview of typical exposure values in current specific occupations.

Methods

The analyses were carried out in the field using an ambulatory measuring system (CUELA) to assess posture combined with one-day self-reported occupational diaries describing the durations of various work tasks. In total, 242 work shifts were measured, representing 81 typical tasks from 16 professions. Knee-straining postures were analysed as daily time intervals for five different postures. The accuracy of the method was examined by comparing the results to measurements of entire work shifts.

Results

Unsupported kneeling was the most widely used knee posture in our sample (median 11.4 % per work shift), followed by supported kneeling (3.0 %), sitting on heels (1.1 %), squatting (0.7 %), and crawling (0.0 %). The daily time spent in knee-straining postures varied considerably, both between the individual occupations, within an occupation (e.g. parquet layers: 0.0–88.9 %), and to some extent even within a single task (e.g. preparation work of floor layers (22.0 ± 23.0 %). The applied measuring method for obtaining daily exposure to the knee has been proven valid and efficient randomly compared with whole-shift measurements (p = 0.27).

Conclusions

The daily degree of postural exposure to the knee showed a huge variation within the analysed job categories and seemed to be dependent on the particular tasks performed. The results of this study may help to develop an exposure matrix with respect to occupational knee-straining postures. The tested combination of task-based measurement and diary information may be a promising option for providing a cost-effective assessment tool.

A comparison of the movement characteristics between the kneeling gait and the normal gait in healthy adults

BACKGROUND

Trainings of the kneeling position, such as standing exercise on the knees and kneeling gait, have been anecdotally used in physical therapy to improve postural control of patients with various pathological conditions. However, clinical evidence is lacking and the movement characteristics of these kneeling trainings have not been well explored. The purpose of this study is to clarify the movement characteristics of the kneeling gait compared with the normal gait.

METHODS

Twenty healthy volunteers (10 men and 10 women) aged 22-34 years were recruited. Participants were required to perform the kneeling gait and the normal gait at a self-selected comfortable speed on the treadmill. Surface electromyograms (EMG) and center of mass (COM) displacements were measured during each task.

RESULTS

The EMGs of the gait-related proximal muscles during the kneeling gait were greater than during the normal gait, even at a comfortable speed. The COM displacement to the lateral direction was longer during the kneeling gait than it was during the normal gait. Furthermore, mechanical energy efficiency during the kneeling gait was less than that during the normal gait.

CONCLUSION

The results suggest that the kneeling gait is an effective exercise to strengthen the gait-related proximal muscles. The increased muscle activities during the kneeling gait were probably due to the compensatory movements of the trunk and the pelvis.

Evaluation of two working methods for screed floor layers on musculoskeletal complaints, work demands and workload

Screed floors are bound by sand-cement (SF) or by anhydrite (AF). Sand-cement floors are levelled manually and anhydrite floors are self-levelling and therefore differences in work demands and prevalences of musculoskeletal complaints might occur. The objective was to assess among SF layers and AF layers (1) the prevalence of musculoskeletal complaints and (2) the physical work demands, energetic workload, perceived workload and discomfort. A questionnaire survey and an observational field study were performed. Compared with AF layers (n = 35), SF layers (n = 203) had higher, however, not statistically significant different, prevalences of neck (20% vs. 7%), shoulder (27% vs. 13%), low back (39% vs. 26%) and ankles/feet (9% vs. 0%) complaints. Sand-cement-bound screed floor layers (n = 18) bent and kneeled significantly longer (Δ77 min and Δ94 min; respectively), whereas AF layers (n = 18) stood significantly longer (Δ60 min). The work demands of SF layers exceeded exposure criteria for low back and knee complaints and therefore new working measures should be developed and implemented.

PRACTITIONER SUMMARY

In comparison with anhydrite-bound screed floor layers, sand-cement-bound screed floor layers exceeded exposure criteria for work-related low back and knee complaints. New working methods and measures for sand-cement-bound screed floor layers should be developed and implemented to reduce the risk for work-related musculoskeletal complaints.

MR Imaging of Intra- and Periarticular Cyst-Like Lesions of the Knee Joint in Workers with Occupational Kneeling

Objective. To determine the risk of intra- and periarticular cyst-like lesions of the knee joint in occupational kneeling. Methods. Magnetic resonance imaging of both knees (n = 282) was conducted in 92 male floor layers and 49 male graphic designers (referents), with a mean age of 55.6 years (range 42–70 years). The prevalence of cyst-like lesions was computed among floor layers and graphic designers, respectively, and associations with occupation summarized by odds ratio (OR) with 95% confidence intervals (CIs). Using logistic regression, models were adjusted for age, body mass index, knee injuries, and knee-straining sports. Results. Floor layers had a significantly higher prevalence of cyst-like lesions in the posterior part of the knee joint compared to graphic designers (OR 2.70, 95% CI 1.50–4.84). Floor layers also had a higher prevalence of fluid collections in the popliteus tendon recess (OR 2.17, 95% CI 0.99–4.77) and large cystic lesions of the popliteus muscle (OR 3.83, 95% CI 0.78–18.89). The prevalence of cystic lesions in the anterior part of the knee joint was low among floor layers (8.7%) and there was no significant difference between the two trade groups (P = 0.34). Conclusions. Occupational kneeling increases the risk of cyst-like lesions in the posterior part of the knee joint.

Relationship between years in the trade and the development of radiographic knee osteoarthritis and MRI-detected meniscal tears and bursitis in floor layers. A cross-sectional study of a historical cohort

OBJECTIVES

An increased risk of developing knee disorders including radiographic knee osteoarthritis (OA) have been shown among workers with kneeling working demands. There may also be a dose-related association between duration of employment in occupations with kneeling work and development of radiographic knee OA and magnetic resonance imaging (MRI)-detected meniscal tears and bursitis.

DESIGN

A cross-sectional study of a historical cohort.

SETTING

Members of the trade unions for floor layers and graphic designers in Denmark.

PARTICIPANTS

92 male floor layers and 49 graphic designers aged 36-70 years were randomly selected among participants from a clinical and radiographic study of 156 floor layers and 152 graphic designers.

OUTCOME MEASURES

Radiographic tibiofemoral (TF) and patellofemoral (PF) knee-OA and MRI-detected meniscal tears and bursitis. Results were adjusted for age, earlier knee traumas, sports activities and body mass index in logistic regression models. Association between TF OA and years in the floor-laying trade was graphically examined by a restricted cubic spline with four knots.

RESULTS

Increase in number of years with exposure to kneeling work is associated with radiographic TF knee OA with ORs 0.7, 95% CI 0.07 to 4.42; OR 1.89, 95% CI 0.29 to 12.3; OR 4.82, 95% CI 1.38 to 17 for <20 years, 20-30 years and >30 years of kneeling work, respectively. MRI-verified medial meniscal tears was increased among subjects with kneeling work with OR 1.96, 95% CI 0.79 to 4.88 to OR 4.73, 95% CI 1.16 to 19.4 but was not associated with duration of employment. Periarticular bursitis was increased in subjects with <20 years of kneeling working activity. Lateral meniscal tears and PF knee OA were not associated with duration of kneeling working activity or with kneeling work in general.

CONCLUSIONS

The findings suggest a dose-response relationship for radiographic TF knee OA in floor layers with a significant amount of kneeling work and an increase of MRI-verified medial meniscal tears among workers with kneeling work.