Occupation as a risk factor for knee disorders

The Correlation of Frequency of Work-Related Disorders with Type of Work among Polish Employees

Musculoskeletal disorders have a significant negative impact on the quality of life of the population. These conditions, as well as other work-related disorders, generate costs associated with treatment and work absence, which makes it a growing problem in industrialized countries. Available data from studies on individual populations of workers indicate a higher incidence of certain symptoms in these groups. Due to the lack of studies on the general population, we aimed to perform the preliminary study evaluating the occurrence of pain and work-related conditions depending on the type of occupational work among Polish employees to identify further possible areas for research. Data was collected using an electronic self-administered questionnaire, which was distributed in groups bringing together various professionals. The data obtained from 379 participants have been analyzed and divided according to performed work into sedentary, forced posture, standing, physical and requiring physical activity. Our study reveals a correlation between the frequency of work-related disorders and type of work performed in the Polish population. A significant correlation between the type of occupational work and prevalence of ankle, knee and shoulder pain, as well as heavy legs or upper limb paresthesia was found. According to our findings, female employees may be more vulnerable to lower limb symptoms. A place of residence also seems to affect the prevalence of upper back pain and heavy legs. The analysis also showed a correlation between the occurrence of hip, knee and ankle pain and the level of education of the participants. Surprisingly, lower extremity paresthesia was significantly more common among participants undertaking additional physical activity, compared to non-physically active respondents.

Raman needle arthroscopy for in vivo molecular assessment of cartilage

The development of treatments for osteoarthritis (OA) is burdened by the lack of standardized biomarkers of cartilage health that can be applied in clinical trials. We present a novel arthroscopic Raman probe that can "optically biopsy" cartilage and quantify key extracellular matrix (ECM) biomarkers for determining cartilage composition, structure, and material properties in health and disease. Technological and analytical innovations to optimize Raman analysis include (1) multivariate decomposition of cartilage Raman spectra into ECM-constituent-specific biomarkers (glycosaminoglycan [GAG], collagen [COL], water [H₂ O] scores), and (2) multiplexed polarized Raman spectroscopy to quantify superficial zone (SZ) COL anisotropy via a partial least squares-discriminant analysis-derived Raman collagen alignment factor (RCAF). Raman measurements were performed on a series of ex vivo cartilage models: (1) chemically GAG-depleted bovine cartilage explants (n = 40), (2) mechanically abraded bovine cartilage explants (n = 30), (3) aging human cartilage explants (n = 14), and (4) anatomical-site-varied ovine osteochondral explants (n = 6). Derived Raman GAG score biomarkers predicted 95%, 66%, and 96% of the variation in GAG content of GAG-depleted bovine explants, human explants, and ovine explants, respectively (p < 0.001). RCAF values were significantly different for explants with abrasion-induced SZ COL loss (p < 0.001). The multivariate linear regression of Raman-derived ECM biomarkers (GAG and H₂ O scores) predicted 94% of the variation in elastic modulus of ovine explants (p < 0.001). Finally, we demonstrated the first in vivo Raman arthroscopy assessment of an ovine femoral condyle through intraarticular entry into the synovial capsule. This study advances Raman arthroscopy toward a transformative low-cost, minimally invasive diagnostic platform for objective monitoring of treatment outcomes from emerging OA therapies.

Detection of kneeling and squatting during work using wireless triaxial accelerometers

Occupational kneeling and squatting are well-documented risk factors for knee disorders. A method using 3 wireless accelerometers to detect and discriminate kneeling and squatting during work were developed based on data from a semi-standardised laboratory protocol. The method was tested for validity under free-living working conditions. The developed method showed high sensitivity (88-99%) and specificity (98-99%) for detection of kneeling and squatting during the semi-standardised laboratory conditions. During free-living working conditions, kneeling showed very high sensitivity (94%) and specificity (99%), while squatting results were non-conclusive due to limited duration of squatting during the free-living working conditions. This method shows great promise for long-term technical measurement of kneeling and squatting during normal working conditions using wireless accelerometers. The method opens up possibilities for using technical measurements to provide valid exposure assessments and intervention evaluations of kneeling and squatting, as well as increased feasibility for technical measurements in large cohort studies. Practitioner summary: Quantification of kneeling and squatting during work is important for prevention, but limited by either imprecise or costly methods. This study developed and validated an inexpensive wireless accelerometer-based measurement method that can be used by practitioners and researchers for long-term measurements of kneeling and squatting during free-living working conditions.

Ageing and Osteoarthritis

The increase in global lifespan has in turn increased the prevalence of osteoarthritis which is now the most common type of arthritis. Cartilage tissue located on articular joints erodes during osteoarthritis which causes pain and may lead to a crippling loss of function in patients. The pathophysiology of osteoarthritis has been understudied and currently no disease modifying treatments exist. The only current end-point treatment remains joint replacement surgery. The primary risk factor for osteoarthritis is age. Clinical and basic research is now focused on understanding the ageing process of cartilage and its role in osteoarthritis. This chapter will outline the physiology of cartilage tissue, the clinical presentation and treatment options for the disease and the cellular ageing processes which are involved in the pathophysiology of the disease.

Prevalence of musculoskeletal disorders in subjects not exposed to biomechanical overload

BACKGROUND

Data on the prevalence of work-related musculoskeletal disorders (WMSDs) in groups of unexposed subjects may serve for comparison in studies on risk/damage in groups of exposed subjects and for the planning of preventive interventions.

OBJECTIVES

To assess the musculoskeletal health status in a group of working subjects not exposed to biomechanical overload.

METHODS

Medical histories were collected by occupational health physicians as part of an active health surveillance program. An ad hoc questionnaire was administered to the subjects to detect musculoskeletal disorders.

RESULTS

The sample consisted of 1023 subjects (605 females and 418 males) with a mean age of 40 years. The prevalence of acute low back pain and disc hernia was 4% and 5.6% respectively; 4.3% of subjects were affected by at least one disorder of the upper limbs while the prevalence of knee disorders was 1.7%. Standardized data proved to be in line with previous studies with the exception of a greater prevalence of shoulder disorders and disc hernia.

CONCLUSIONS

WMSDs occur ubiquitously across the general working population unexposed to biomechanical overload. Such findings represent a valid reference for groups of exposed working subjects, in that any excess of such disorders/pathology may be due to specific work conditions.

The effect of numbness on outcome from total knee replacement

INTRODUCTION Some patients report continuing pain and functional limitations after total knee replacement (TKR). While numbness around the TKR scar is common, the impact of numbness is less clear. One particular activity that could be influenced by numbness is kneeling. The aim of this study was to explore the impact of numbness around TKR scars on health related quality of life and kneeling ability. METHODS Fifty-six patients were recruited one year after primary TKR. Sensation around the knee was assessed through patient self-reporting, monofilament testing and vibration, and patients' distress was measured on a visual analogue scale. Patient reported outcome measures (PROMs) including the Western Ontario and McMaster Universities (WOMAC^®) index, the Knee injury and Osteoarthritis Outcome Score (KOOS), the painDETECT^® (Pfizer, Berlin, Germany) questionnaire and the EQ-5D™ (EuroQol, Rotterdam, Netherlands) questionnaire were used. Participants were also asked about kneeling ability. RESULTS While 68% of patients reported numbness around their TKR scar, there was no statistically significant correlation between numbness and distress at numbness (self-report: 0.23, p=0.08; monofilament: 0.15, p=0.27). Furthermore, numbness did not correlate significantly with joint specific PROMs (WOMAC^®: 0.21, p=0.13; KOOS: 0.18, p=0.19). However, difficulty with kneeling did correlate with both self-reported numbness (0.36, p=0.020) and worse PROM scores (WOMAC^® pain subscale: 0.62, p<0.001; KOOS: 0.64, p<0.001). CONCLUSIONS Numbness after knee replacement is common but is not associated with worse patient reported outcomes.

Adapting to floor sitting and kneeling

This short practical article suggests that for those unused to ground living, increasing their time spent in sitting or kneeling postures may improve their adaptation of their passive and active joint structures by using low stools, mats, blocks, yoga bricks, bolsters/cushions, and rolled towels. A very slow approach to adaptation and a deliberate reduction of extremes of available lower limb joint range, in the beginning of the process, is likely to reduce possible tissue overload injury risk.

Race- and Sex-Specific Incidence Rates and Predictors of Total Knee Arthroplasty: Seven-Year Data From the Osteoarthritis Initiative

OBJECTIVE

To determine race- and sex-specific rates of total knee arthroplasty (TKA) and to document independent effects of demographic factors on TKA incidence in a population with radiographically confirmed osteoarthritis (OA).

METHODS

We used data from the Osteoarthritis Initiative, a US-based, multicenter longitudinal study of knee OA. We selected subjects with radiographic symptomatic OA at baseline and determined TKA incidence rates (ratio of TKAs to time at risk for TKA) over 84 months of followup. We used multivariable Poisson regression to identify independent associations between demographic factors and TKA utilization.

RESULTS

During the study period there were 223 TKAs among 1,915 subjects for an incidence of 1.9% (95% confidence interval [95% CI] 1.7-2.2%). The overall rate was 1.9% (95% CI 1.5-2.3%) in men versus 2.0% (95% CI 1.7-2.3%) in women, and 2.2% (95% CI 1.9-2.6%) in whites versus 1.0% (95% CI 0.7-1.5%) in nonwhites. We observed a statistically significant interaction between sex and age (stratified at <65 and ≥65 years at end of followup), wherein male sex was associated with decreased risk of TKA for younger participants (relative risk [RR] 0.32) but not for older participants. Nonwhite race was associated with a decreased risk of TKA for both younger (RR 0.32) and older (RR 0.43) participants.

CONCLUSION

Our finding that nonwhites were less likely to undergo TKA than whites in adjusted analyses confirms racial differences observed in population-based studies and underscores the need for interventions to address lower use of TKA among nonwhites with OA.

Occupational Exposure to Knee Loading and the Risk of Osteoarthritis of the Knee: A Systematic Review and a Dose-Response Meta-Analysis

BACKGROUND

Osteoarthritis of the knee is considered to be related to knee straining activities at work. The objective of this review is to assess the exposure dose-response relation between kneeling or squatting, lifting, and climbing stairs at work, and knee osteoarthritis.

METHODS

We included cohort and case-control studies. For each study that reported enough data, we calculated the odds ratio (OR) per 5,000 hours of cumulative kneeling and per 100,000 kg of cumulative lifting. We pooled these incremental ORs in a random effects meta-analysis.

RESULTS

We included 15 studies (2 cohort and 13 case-control studies) of which nine assessed risks in more than two exposure categories. We considered all but one study at high risk of bias. The incremental OR per 5,000 hours of kneeling was 1.26 (95% confidence interval 1.17-1.35, 5 studies, moderate quality evidence) for a log-linear exposure dose-response model. For lifting, there was no exposure dose-response per 100,000 kg of lifetime lifting (OR 1.00, 95% confidence interval 1.00-1.01). For climbing, an exposure dose-response could not be calculated.

CONCLUSION

There is moderate quality evidence that longer cumulative exposure to kneeling or squatting at work leads to a higher risk of osteoarthritis of the knee. For other exposure, there was no exposure dose-response or there were insufficient data to establish this. More reliable exposure measurements would increase the quality of the evidence.

Biomechanics of hyperflexion and kneeling before and after total knee arthroplasty

The capacity to perform certain activities is frequently compromised after total knee arthroplasty (TKA) due to a functional decline resulting from decreased range of motion and a diminished ability to kneel. In this manuscript, the current biomechanical understanding of hyperflexion and kneeling before and after TKA will be discussed. Patellofemoral and tibiofemoral joint contact area, contact pressure, and kinematics were evaluated in cadaveric studies using a Tekscan pressure measuring system and Microscribe. Testing was performed on intact knees and following cruciate retaining and posterior stabilized TKA at knee flexion angles of 90°, 105°, 120°, and 135°. Three loading conditions were used to simulate squatting, double stance kneeling, and single stance kneeling. Following TKA with double stance kneeling, patellofemoral contact areas did not increase significantly at high knee flexion angle (135°). Kneeling resulted in tibial posterior translation and external rotation at all flexion angles. Moving from double to single stance kneeling tended to increase pressures in the cruciate retaining group, but decreased pressures in the posterior stabilized group. The cruciate retaining group had significantly larger contact areas than the posterior stabilized group, although no significant differences in pressures were observed comparing the two TKA designs (p < 0.05). If greater than 120° of postoperative knee range of motion can be achieved following TKA, then kneeling may be performed with less risk in the patellofemoral joint than was previously believed to be the case. However, kneeling may increase the likelihood of damage to cartilage and menisci in intact knees and after TKA increases in tibiofemoral contact area and pressures may lead to polyethyelene wear if performed on a chronic, repetitive basis.

Comparison of stress on knee cartilage during kneeling and standing using finite element models

Kneeling is a common activity required for both occupational and cultural reasons and has been shown to be associated with an increased risk of knee disorders. While excessive contact pressure is considered to be a possible aggressor, it is not clear whether and to what extent stress on the cartilage during kneeling is different from that while standing. In this study, finite element models of the knee joint for both kneeling and standing positions were constructed. The results indicated differences in high-stress regions between kneeling and standing. And both the peak von-Mises stress and contact pressure on the cartilage were larger in kneeling. During kneeling, the contact pressure reached 4.25 MPa under a 300 N compressive load. It then increased to 4.66 MPa at 600 N and 5.15 MPa at 1000 N. Changing the Poisson's ratio of the cartilage, which represents changes in compressibility caused by different loading rates, was found to have an influence on the magnitude of stress.

Sonoanatomic variation of pes anserine bursa

BACKGROUND

The pes anserine bursa lies beneath the pes anserine tendon, which is the insertional tendon of the sartorius, gracilis, and semitendinosus muscles on the medial side of the tibia, but it can lie in different sites in the medial knee. Accurate diagnosis of the position of the bursa is critical for diagnostic and therapeutic goals. The aim of this study was to evaluate sonoanatomic variations of the pes anserine bursa in the medial knee.

METHODS

One hundred seventy asymptomatic volunteers were enrolled in this study. Using ultrasound imaging (transverse approach, 7-13 MHz linear array probe) the sonoanatomic position of the pes anserine bursa and its relation to the pes anserine tendon were evaluated. Additionally, we evaluated the sonoanatomic variation of the saphenous nerve.

RESULTS

The position of the pes anserine bursa was between the medial collateral ligament and the pes anserine tendons in 21.2%/18.8% (males/females) of subjects; between the pes anserine tendons and the tibia in 67.1%/64.7% (m/f); and among the pes anserine tendons in 8.2%/12.9% (m/f). No significant differences in the position of the bursa existed between males and females. The saphenous nerve was found within the pes anserine tendons in 77.6%/74.1% (m/f) of subjects, but outside the pes anserine tendons in 18.8%/15.3% (m/f). Visibility of sonoanatomic structures was not related to either gender or BMI.

CONCLUSIONS

Ultrasound provides very accurate information about variations in the pes anserine bursa and the saphenous nerve. This suggests that our proposed ultrasound method can be a reliable guide to facilitate approaches to the medial knee for diagnostic and therapeutic objectives.

Risk factors for meniscal tears: a systematic review including meta-analysis

STUDY DESIGN

Systematic review with meta-analysis.

OBJECTIVES

To review and critically appraise the literature for factors that increase the risk for meniscal tears.

BACKGROUND

Meniscal tears are an important cause of disability and time lost from work, and are associated with a 4-fold increase in the long-term risk of knee osteoarthritis. Knowledge of the risk factors that lead to meniscal tears can help to correctly diagnose knee injuries and is important to the development of prevention strategies for knee osteoarthritis.

METHODS

A search of the Cochrane Database of Systematic Reviews, MEDLINE, and Embase, from 1950 to January 2012, and a hand search of reference lists of all initially selected studies, without restriction on language or date of publication, were conducted. Prospective, retrospective, and case-control studies that included individuals over 16 years of age, who had no previous meniscal injuries or surgeries, were selected. A meta-analysis for 17 risk factors was performed. Where considerable heterogeneity among studies was present or the data did not provide sufficient information to perform a meta-analysis, a qualitative synthesis was conducted.

RESULTS

Eleven studies, with a total of 7358 participants, were selected for systematic review. Data were available for meta-analysis for 10 of the 11 studies. Qualitative analysis was conducted using data from 3 of the 11 studies. Results showed strong evidence that age (older than 60 years), gender (male), work-related kneeling and squatting, and climbing stairs (greater than 30 flights) were risk factors for degenerative meniscal tears. We also found strong evidence that playing soccer and playing rugby were strong risk factors for acute meniscal tears. Waiting longer than 12 months between the anterior cruciate ligament injury and reconstructive surgery was a strong risk factor for a medial meniscal tear but not for a lateral meniscal tear.

CONCLUSION

The literature indicates a number of risk factors leading to either degenerative or acute meniscal tears, with some of these factors being potentially modifiable.

LEVEL OF EVIDENCE

Prognosis, level 2a.

Prevalence of knee bursitis in the workforce

BACKGROUND

Knee bursitis (KB) is a common disorder in specific occupations requiring frequent and/or sustained kneeling postures.

AIMS

To assess the prevalence of KB in the general working population.

METHODS

Between 2002 and 2005, a total of 3710 workers of a French region were randomly included in the study. A standardized physical examination of the knee was performed when knee pain was reported by the worker during the preceding 12 months. The criteria for diagnosis of KB were (i) the presence of pain and/or tenderness in the anterior face of the knee at the date of the examination (or for at least 4 days in the preceding week) and (ii) the presence of swelling and/or pressure-induced pain of the pre- or infra-patellar bursa. Occupational risk factors were assessed by a self-administered questionnaire.

RESULTS

The prevalence of uni- or bilateral cases of knee bursitis was low: 0.6% [0.2-0.9] in men and 0.2% [0.0-0.6] in women. The highest prevalence was observed in the construction sector (2.3% [0.8-5.4]) and in the food and meat processing industries (1.4% [0.4-3.5)]. More blue-collar workers were affected than other occupation categories (0.8% [0.3-1.2] versus 0.1% [0.0-0.4]).

CONCLUSIONS

The study showed a concentration of cases among male workers exposed to heavy workloads and frequent kneeling.

The influence of cyclic concentric and eccentric submaximal muscle loading on cell viability in the rabbit knee joint

BACKGROUND

Cartilage loading is associated with the onset and progression of osteoarthritis and cell death may play an important role in these processes. Although much is known about cell death in joint impact loading, there is no information on joints loaded by muscular contractions. The aim of this study was to evaluate the influence of muscle generated eccentric and concentric submaximal joint loading on chondrocyte viability. We hypothesised that eccentric muscle activation leads to increased cell death rates compared to concentric loading and to controls.

METHODS

16 rabbits received either 50 min of uni-lateral, cyclic eccentric (n=8) or concentric (n=8) knee loading. Muscle activation for these dynamic conditions was equivalent to an activation level that produced 20% of maximum isometric force. Contralateral joints served as unloaded controls. Cell viability was assessed using confocal microscopy.

FINDINGS

Eccentric contractions produced greater knee loading than concentric contractions. Sub-maximal contractions caused a significant increase in cell death in the loaded knees compared to the unloaded controls, and eccentric loading caused significantly more cell death than concentric loading.

INTERPRETATION

Cyclic sub-maximal muscle loading of the knee caused increased chondrocyte death in rabbits. These findings suggest that low levels of joint loading for prolonged periods, as occurs in endurance exercise or physical labour, may cause chondrocyte death, thereby predisposing joints to degeneration.

Burden of work-related knee disorders in Washington State, 1999 to 2007

OBJECTIVE

To describe the burden of knee work-related musculoskeletal disorders (WMSDs).

METHODS

Knee WMSDs were identified using Washington State Fund workers' compensation data from 1999 to 2007 and analyzed by cost, industry, occupation, and claims incidence rates.

RESULTS

Knee WMSDs accounted for 7% of WMSD claims and 10% of WMSD costs. The rate of decline in claims incidence rates for knee WMSDs was similar to the rate of decline for all other WMSDs. Industries at highest risk for knee WMSDs included construction and building contractors. Occupations of concern included carpenters and truck drivers in men and nursing aides and housekeepers in women.

CONCLUSIONS

Between 1999 and 2007, Washington State Fund knee WMSDs were widespread and associated with a large cost. Identification of specific occupational knee WMSD risk factors in high-risk industries is needed to guide prevention efforts.

Effects on tibiofemoral biomechanics from kneeling

BACKGROUND

Repetitive kneeling in certain occupations, hobbies and cultures is associated with tibiofemoral joint osteoarthritis. The biomechanics of kneeling is therefore of interest. This cadaveric study investigated tibiofemoral joint contact areas, pressures, and kinematics in response to kneeling.

METHODS

Five human cadaveric knees were subjected to simulated kneeling at flexion angles of 90°, 105°, 120°, and 135°. Different anterior forces were applied to the knee to simulate crouching (no force), double stance kneeling (339N of force), and single stance kneeling (678N of force). Tibiofemoral joint kinematics, contact areas, and pressures were measured.

FINDINGS

Kneeling produced tibial posterior translation and external rotation. Posterior translation was significantly less at 90° than at higher flexion angles (P<0.05). Posterior translation and external rotation were significantly greater moving from crouching to double stance kneeling when compared to moving from double to single stance kneeling (P<0.05). Double and single stance kneeling increased contact areas and pressures significantly when compared to crouching (P<0.05). Pressures also increased significantly moving from double to single stance kneeling (P<0.05).

INTERPRETATION

Kneeling produces less tibial posterior translation at 90° than at higher flexion angles primarily due to posterior cruciate ligament biomechanics. Tibial external rotation results from posterior cruciate ligament biomechanics and differences between medial and lateral compartment anatomy. Different anatomical constraints allow significantly less posterior translation and external rotation moving from double to single stance kneeling is a result of increased pressure with kneeling likely contributes to the development of tibiofemoral osteoarthritis, and single stance kneeling may be more deleterious than double stance kneeling.

Occupational risk factors for osteoarthritis of the knee: a meta-analysis

INTRODUCTION

Systematic reviews agree that knee osteoarthritis (OA) is related to occupational activities, but have not quantified the overall risks.

METHODS

Systematic review of observational studies of knee OA and occupation. Job titles, elite sport, heavy work, kneeling, and other activities were included. Relative risk estimate and 95% confidence interval (CI) compared to sedentary work were retrieved or calculated for meta-analysis. Publication bias was examined with Egger tests and heterogeneity was determined with I(2) values and Q tests. Subgroup analysis was performed to examine causes of heterogeneity. A random effects model was performed to combine the data.

RESULTS

Studies of knee OA (n=51), persistent knee pain (n=12) and knee OA progression (n=3) were retrieved. Occupational risks for knee OA were examined in a total of 526,343 subjects in 8 cohort/prospective/longitudinal studies, 25 cross-sectional studies and 18 case control studies. The overall odds ratio (OR) was 1.61 (95% CI 1.45-1.78) with significant heterogeneity (I(2)=83.6%). Study designs showed a positive association between knee OA and occupational activities; cohort (OR 1.38, 95% CI 1.10-1.74), cross-sectional (OR 1.57, 95% CI 1.37-1.81) and case control (OR 1.80, 95% CI 1.48-2.19). Overall there was evidence of publication bias (P<0.0001) which was apparent in the cross-sectional and case control studies (P<0.0001 and P=0.0247 respectively).

CONCLUSIONS

Some occupational activities increase the risk of knee OA, although the influences of publication bias and heterogeneity are important limitations of this study. Prospective studies would greatly improve the evidence base.

A review of occupational knee disorders

INTRODUCTION

Lower extremity knee disorders, like other cumulative disorders of the body, build up over time through cumulative exposures. 2006 data from the U.S. Bureau of Labor Statistics reveal that cumulative knee disorders account for 65% of lower extremity musculoskeletal disorders and 5% of total body musculoskeletal disorders.

METHODS

The objective of the literature review was to find papers on work-related musculoskeletal disorders (WMSDs) common to the knee region. From these, symptoms of the disorders, affected industries, and potential risk factors were assessed.

RESULTS

A review of the literature divulges that knee disorders primarily consist of bursitis, meniscal lesions or tears, and osteoarthritis. Though kneeling and squatting are considered to be two of the primary risk factors correlated to these knee disorders, 12 other risk factors should also be contemplated. These 14 contributing risk factors include both occupational (extrinsic) and personal (intrinsic) variables that affect the labor industries. Example industries include mining, construction, manufacturing, and custodial services where knee bending postural activities exist as a commonality.

CONCLUSION

The understanding of the types of knee disorders, the affected occupations, and the job related risk factors will allow ergonomic practitioners and researchers to create and adjust work environments for the detection and lessening of knee work-related musculoskeletal risk. Further studies need to be conducted to (1) justify the presence of risk from certain risk factors and (2) enhance the understanding of risk factor dose-response levels and their temporal development.

Individual and occupational risk factors for knee osteoarthritis: results of a case-control study in Germany

INTRODUCTION

A number of occupational risk factors are discussed in relation to the development and progress of knee joint diseases (for example, working in a kneeling or squatting posture, lifting and carrying heavy weights). Besides the occupational factors, a number of individual risk factors are important. The distinction between work-related and other factors is crucial in assessing the risk and in deriving preventive measures in occupational health.

METHODS

In a case-control study, patients with and without symptomatic knee osteoarthritis (OA) were questioned by means of a standardised questionnaire complemented by a semi-standardised interview. Controls were matched and assigned to the cases by gender and age. Conditional logistic regression was used in analysing data.

RESULTS

In total, 739 cases and 571 controls were included in the study. In women and men, several individual and occupational predictors for knee OA could be described: obesity (odds ratio (OR) up to 17.65 in women and up to 12.56 in men); kneeling/squatting (women, OR 2.52 (>8,934 hours/life); men, 2.16 (574 to 12,244 hours/life), 2.47 (>12,244 hours/life)); genetic predisposition (women, OR 2.17; men, OR 2.37); and sports with a risk of unapparent trauma (women, OR 2.47 (>or=1,440 hours/life); men, 2.58 (>or=3,232 hours/life)). In women, malalignment of the knee (OR 11.54), pain in the knee already in childhood (OR 2.08), and the daily lifting and carrying of loads (>or=1,088 tons/life, OR 2.13) were related to an increased OR; sitting and smoking led to a reduced OR.

CONCLUSIONS

The results support a dose-response relationship between kneeling/squatting and symptomatic knee OA in men and, for the first time, in women. The results concerning general and occupational predictors for knee OA reflect the findings from the literature quite well. Yet occupational risks such as jumping or climbing stairs/ladders, as discussed in the literature, did not correlate with symptomatic knee OA in the present study. With regards to occupational health, prevention measures should focus on the reduction of kneeling activities and the lifting and carrying of loads as well as general risk factors, most notably the reduction of obesity. More intervention studies of the effectiveness of tools and working methods for reducing knee straining activities are needed.

Leg Strength Comparison between Younger and Middle-age Adults

Although a risk of occupational musculoskeletal diseases has been identified with age-related strength degradation, strength measures from working group are somewhat sparse. This is especially true for the lower extremity strength measures in dynamic conditions (i.e., isokinetic). The objective of this study was to quantify the lower extremity muscle strength characteristics of three age groups (young, middle, and the elderly). Total of 42 subjects participated in the study: 14 subjects for each age group. A commercial dynamometer was used to evaluate isokinetic and isometric strength at ankle and knee joints. 2 × 2 (Age group (younger, middle-age, and older adult groups) × Gender (male and female)) between-subject design and Post-hoc analysis were performed to evaluate strength differences among three age groups. Post-hoc analysis indicated that, overall, middle-age workers' leg strengths (i.e. ankle and knee muscles) were significantly different from younger adults while middle-age workers' leg strengths were virtually identical to older adults' leg strengths. These results suggested that, overall, 14 middle-age workers in the present study could be at a higher risk of musculoskeletal injuries. Future studies looking at the likelihood of musculoskeletal injuries at different work places and from different working postures at various age levels should be required to validate the current findings. The future study would be a valuable asset in finding intervention strategies such that middle-age workers could stay healthier longer.

Variability in risk factors for knee injury in construction

This study investigated sources of variance in exposure to risk factors for knee pain in a variety of highway construction trades, operations, and tasks. Over 15,000 discrete observations of leg postures and weights handled were made on 120 construction workers in five construction trades, in nine operations over 79 days. The contributions of trade, operation, task, and worker to the variability in work time spent kneeling, squatting, and carrying loads were evaluated with multilevel random effects models. Construction operation and task explained about 20% to 30% of total variation in kneeling, squatting, and carrying loads. There was a large unexplained component of variance thought to represent day-to-day variability of exposure within task. Reliable assessments of knee exposures require multiple days to accommodate the high variability of exposures among operations and tasks and over time. These sources of variability should be carefully considered in efforts to estimate exposures to knee loading for epidemiologic or intervention studies. Homogenous exposure groups are not easily defined from the readily available organizational features of construction work.

Individual and occupational risk factors for knee osteoarthritis - study protocol of a case control study

Background

Knee osteoarthritis (OA) is one of the frequent and functionally impairing disorders of the musculoskeletal system. In the literature, a number of occupational risk factors are discussed as being related to the development and progress of knee joint diseases, e.g. working in kneeling or squatting posture, lifting and carrying of heavy weights. The importance of the single risk factors and the possibility of prevention are currently under discussion. Besides the occupational factors, a number of individual risk factors are important, too. The distinction between work-related factors and individual factors is crucial in assessing the risk and in deriving preventive measures in occupational health. In existing studies, the occupational stress is determined mainly by surveys in employees and/or by making assumptions about individual occupations. Direct evaluation of occupational exposure has been performed only exceptionally.

The aim of the research project ArGon is the assessment of different occupational factors in relation to individual factors (e.g. constitutional factors, leisure time activities, sports), which might influence the development and/or progression of knee (OA). The project is designed as a case control study.

Methods/Design

To raise valid data about the physical stress associated with occupational and leisure time activities, patients with and without knee OA are questioned by means of a standardised questionnaire and an interview. The required sample size was estimated to 800 cases and an equal number of controls. The degree and localisation of the knee cartilage or joint damages in the cases are documented on the basis of radiological, arthroscopic and/or operative findings in a patient record. Furthermore, occupational exposure is analysed at selected workplaces. To evaluate the answers provided in the questionnaire, work analysis is performed.

Discussion

In this research project, specific information on the correlation of occupational and individual factors on the one hand and the current state of knee OA on the other will be analysed in order to describe preventive measures. In addition, information regarding a better evaluation of various forms of physical stress in different occupations will be available. This might lead to more effective prevention strategies.

Patellar blood flow during knee arthroplasty surgical exposure: Intraoperative monitoring by laser doppler flowmetry

Patellofemoral complications following knee arthroplasty are a well-known problem. Patellar ischemia has been suspected to be causative for fracture, anterior knee pain, and patella component failure. The purpose of this study was to assess the influence of knee arthroplasty surgical dissection on patellar blood flow. Patellar blood flow was measured by means of intraosseous laser Doppler flowmetry (LDF) in 10 patients undergoing total knee arthroplasty by a standard medial parapatellar approach. The initial blood flow was 121.6 +/- 114.7 AU. The signal significantly decreased by 71% (p = 0.0051) when the knee was flexed and lost the pulsatile signal pattern in 80%. After arthrotomy, the signal was 100.1 +/- 120.3 AU in extension. The lowest signal was found in flexion and eversion of the patella (mean, 18 +/- 10.7 AU) and all signals lost pulsatility. As compared to the initial values, completion of the soft tissue dissection did not lead to a significant change of the blood flow signal (121.3 +/- 104.8; p = 0.6835). Flexion of the knee joint markedly reduced patellar perfusion. Standard medial parapatellar approach did not significantly change patellar blood flow. This study does not support the theory of postoperative patellar ischemia as a cause of anterior knee pain or patellofemoral problems.

Knee complaints and consequences on work status; a 10-year follow-up survey among floor layers and graphic designers

Background

The purpose of the study was to examine if knee complaints among floor layers predict exclusion from the trade.

Methods

In 1994/95 self-reported data were obtained from a cohort of floor layers and graphic designers with and without knee straining work activities, respectively. At follow-up in 2005 the questionnaire survey was repeated. The study population consisted of 81 floor layers and 173 graphic designers who were presently working in their trades at baseline (1995). All participants were men aged 36–70 years in 2005.

We computed the risk of losing gainful employment in the trade according to occurrence of knee complaints at baseline, using Cox proportional hazard regression adjusted for a number of potential confounding variables. Moreover, the crude and adjusted odds risk ratio for knee complaints according to status of employment in the trade were computed, using graphic designers as reference.

Results

A positive but non-significant association between knee complaints lasting more than 30 days the past 12 months and exclusion from the trade was found among floor layers (Hazard Ratio = 1.4, 95% CI = 0.6–3.5).

The frequency of self-reported knee complaints was lower among floor layers presently at work in the trade in year 2005 (26.3%) compared with baseline in 1995 (41.1%), while the opposite tendency was seen among graphic designers (20.7% vs. 10.7%).

Conclusion

The study suggests that knee complaints are a risk factor for premature exclusion from a knee demanding trade. However, low power of the study precludes strong conclusions. The study also indicates a healthy worker effect among floor layers and a survivor effect among graphic designers.

Habitual floor activities increase risk of knee osteoarthritis

Knee osteoarthritis is a major worldwide public health problem. Mechanical factors generally are considered important in its pathogenesis. Whether floor activities increase the risk of knee osteoarthritis is unclear. We performed a population-based survey to document the association of floor activities with pattern and severity of knee osteoarthritis. We identified 288 women and 288 men 40 years or older from Songkhla province in southern Thailand. We recorded their lifetime histories of four common positions in floor activities: squatting, lotus, side-knee bending, and kneeling. Involvement of osteoarthritis was categorized in three patterns: isolated patellofemoral, isolated tibiofemoral, and combined. We used multinomial logistic regression analysis adjusted for age, gender, body mass index, and smoking status to identify associations between lifetime floor activity and knee osteo-arthritis. Squatting and side-knee bending positions increased the relative risk of radiographic knee osteoarthritis. All types of floor activities except kneeling increased the risk of moderate to severe radiographic knee osteoarthritis. Squatting and lotus positions increased the relative risk of knee pain with radiographic osteoarthritis. Our data suggest habitual lifetime squatting, lotus, and side-knee bending positions increase the risk of knee osteoarthritis.

Is the use of ergonomic measures associated with behavioural change phases?

The aim of this study was to test the hypothesis that the absolute number of completed behavioural change phases (ABP) and the sequentially ordered number of completed behavioural change phases (SBP) are positively associated with the use of ergonomic measures by two groups of stakeholders in bricklaying companies (employers/planners, foremen/bricklayers). The measures, consisting of trestles, bricklaying scaffolds, mast-climbing work platforms and cranes, reduce the physical work demands made upon bricklayers and bricklayers' assistants. Structured interviews were conducted with stakeholders of 27 companies. Ordinal regression of behavioural change phases on the use of ergonomic measures showed a significant increase in both ABP and SBP in relation to increased use of three of the four ergonomic measures (i.e. trestles, bricklaying scaffolds, mast-climbing work platforms) by employers/planners and increased use of one ergonomic measure (i.e. trestles) by foremen/bricklayers. In conclusion, the positive and significant associations between the completed behavioural change phases (ABP and SBP) and use of ergonomic measures differ for the stakeholder groups and between the ergonomic measures. The data suggest that there is a higher chance of increasing the use of ergonomic measures by means of a higher ABP than a higher SBP. It is recommended for activities to be carried out-primarily by employers/planners-to facilitate as many behavioural change phases as possible in order to stimulate actual use of ergonomic measures at worksites.

Impact of railroad ballast type on frontal plane ankle kinematics during walking

Five healthy male subjects walked on a control surface (level concrete), and two sloped rock surfaces (walking ballast-rock about 1.9 cm across; main line ballast-rock about 3.8 cm across) while their rearfoot motion (defined throughout as ankle inversion/eversion as seen from the frontal plane) was measured to determine if the different walking surfaces caused different ankle kinematics. The ballast was placed in 5m long trays that were tilted 7 degrees in the transverse plane. Rearfoot motion was measured while the subjects walked the length of the respective surfaces wearing work boots. A repeated measures ANOVA and a subsequent multiple comparison test revealed that the rearfoot range of motion was significantly greater walking on the main line ballast than walking on either the walking ballast or the level concrete. Meanwhile, the mean range of rearfoot motion for walking ballast was not significantly different from that resulting from walking on concrete. Variability was more than twice as great walking on main line ballast than walking on level concrete. Rearfoot angular velocities walking on level concrete and walking ballast were not significantly different, but both were significantly less than walking on main line ballast. Results suggested that rearfoot motion could be reduced if railroads placed walking ballast where trainmen have to walk as part of their jobs.

Osteoarthritis and meniscus disorders of the knee as occupational diseases of miners

AIM

To determine whether kneeling or squatting for prolonged periods is sufficiently causally associated with an increased risk of injury or degenerative disease of the knee joint as to meet the classic criteria to be considered an occupational disease of coal miners for whom these are or have been routine working postures.

METHOD

Systematic literature searches were made for studies relating to kneeling and squatting as part of the working environment of coal mines and the role of these postures in causation of knee disorders in coal miners, analogous occupations, populations, and communities. The working environment and potentially damaging forces on the knee when kneeling or squatting were described. Papers on the incidence or prevalence of knee disorders in occupational and other groups were scored against five criteria independently by each author, and from this a single consensus score representing the overall strength of evidence given by the research was awarded. The evidence was then weighed against the criteria for an occupational disease.

RESULTS

Nineteen published papers were scored, the majority of which focussed on osteoarthritis as the outcome of interest. Few of the studies found focussed specifically on miners, and those that did tended to involve small numbers of subjects and were carried out before 1960, when the mining population was at its largest but epidemiological evidence of the risk factors for knee disorders was not well established. The non-mining studies in the review represent groups of workers with a similar or lesser kneeling content in their work.

CONCLUSION

The papers reviewed provide sufficient evidence to conclude that work involving kneeling and/or squatting is causally associated with an increased risk of osteoarthritis of the knee. In some of the more recent epidemiologically sound studies, frequent or prolonged kneeling or squatting doubles the general risk of osteoarthritis of the knees found in the general population. This may be of particular importance in welfare and medico-legal situations. There was also evidence to suggest that lifting, in combination with kneeling/squatting, an activity also performed by miners in the course of their work, is associated with an excess risk of osteoarthritis above that attributed to kneeling/squatting alone.

Review of epidemiologic studies on occupational factors and lower extremity musculoskeletal and vascular disorders and symptoms

The epidemiologic literature on lower extremity musculoskeletal disorders (MSDs), vascular disorders, and occupational mechanical factors is relatively sparse, compared to the low back and upper extremities. The present literature review aims to summarize and evaluate the current literature on lower extremity vascular disorders, MSDs, and symptoms, and to update previous literature reviews. A search was conducted in PubMed. Articles were included if they had a lower extremity musculoskeletal outcome, and a workplace factor(s). They were evaluated based upon their generalizability, exposure, and outcome assessments, study design, and controlling of confounders. Most of the literature has focused on osteoarthritis of the hip and knee, whereas not much research has been done examining the feet/ankles and lower legs. Overall, better exposure assessment is needed to examine the causal pathway between occupational factors and MSDs.

Impact of occupational stress and other psychosocial factors on musculoskeletal pain among Chinese offshore oil installation workers

AIMS

To explore the relation between psychosocial factors and musculoskeletal pain in Chinese offshore oil installation workers.

METHODS

Half of all offshore workers (being a representative sample) in a Chinese oil company were invited to complete a self-administered questionnaire providing information on sociodemographic characteristics, occupational stressors, type A behaviour, social support, coping style, health related behaviour, past injuries, and musculoskeletal pain. Factor analysis was used to identify the sources of occupational stress and the domains of type A behaviour and coping style. Logistic regression analyses were used to study the relations between psychosocial factors and musculoskeletal pain in each body region.

RESULTS

The prevalence of musculoskeletal pain over the previous 12 months varied between 7.5% for elbow pain and 32% for low back pain; 56% workers had at least one complaint. Significant associations were found between various psychosocial factors and musculoskeletal pain in different body regions after adjusting for potential confounding factors. Occupational stressors, in particular stress from safety, physical environment, and ergonomics, were important predictors of musculoskeletal pain, as was coping by eating behaviour.

CONCLUSIONS

These observations supported the widely accepted biopsychosocial model of musculoskeletal disorders and suggested that in future studies of work related musculoskeletal disorders, psychosocial factors must be given due consideration.

Weight changes and the risk of knee osteoarthritis requiring arthroplasty

OBJECTIVE

To examine the effect of weight changes between 20 and 50 years of age on the risk of severe knee osteoarthritis (OA) requiring arthroplasty.

SUBJECTS AND METHODS

Cases were 55-75 year old men and women (n = 220) having had knee arthroplasty for primary osteoarthritis at the Kuopio University Hospital in 1992-93. Controls (n = 415) were randomly selected from the population of Kuopio Province. Weight at the age of 20, 30, 40, and 50 years was collected retrospectively with a postal questionnaire.

RESULTS

After adjustment for age, sex, history of physical workload, recreational physical activity, and previous knee injury, weight gain resulting to a shift from normal body mass index (BMI < or =25 kg/m(2)) to overweight (BMI >25 kg/m(2)) was associated with a higher relative risk of knee OA requiring arthroplasty than persistent overweight from 20-50 years of age, compared with those with normal relative weight during the corresponding age period. The odds ratios (OR) were 3.07 (95% confidence interval 1.87 to 5.05) for those with normal weight at the age of 20 years and overweight at two or three of the ages 30, 40 or 50 years, 3.15 (1.85 to 5.36) for those with overweight from the age of 30 years, and 2.37 (1.21 to 4.62) for those with overweight from the age of 20 years, respectively.

CONCLUSION

In adult life, a shift from normal to overweight may carry a higher risk for knee OA requiring arthroplasty than does constant overweight.

Risk factors for osteoarthritis: understanding joint vulnerability

Joint damage occurs when structures protecting the joint fail. Because osteoarthritis consists of end-stage joint damage, I propose that risk factors for disease can be best understood as either impairments of joint protectors, increasing joint vulnerability, or as factors that excessively load the joint, leading to injury. I review current knowledge using this paradigm, separating factors into those increasing joint vulnerability (malalignment, muscle weakness, genetic and ethnic predispositions, aging) and those that cause excessive loading (obesity; certain physical activities). Osteoarthritis and cartilage loss can occur without pain. This review focuses separately on factors associated with pain in those with osteoarthritis. To identify sources of pain in osteoarthritis, recent studies have compared magnetic resonance imaging findings of people with osteoarthritis with and without pain, focusing on structures known to have nociceptive innervations. Those with pain are more likely to have effusions, bone marrow lesions, synovial hypertrophy, and tendinitis and bursitis around the joint. This review creates a new paradigm for understanding risk factors for osteoarthritis, using joint vulnerability and loading as a framework and focuses separately on the emerging investigative area of sources of pain.

Observed kneeling ability after total, unicompartmental and patellofemoral knee arthroplasty: perception versus reality

Kneeling is an important function of the knee, but little information is available on ability to kneel after different knee arthroplasty procedures. Previous work has asked patients about their kneeling ability; in this study it was objectively assessed. One hundred and twenty two patients - 38 having had total knee replacement (TKR), 53 unicompartmental knee replacement (UKR), 31 patello-femoral replacement (PFR) - were observed trying to kneel at 90 degrees on a chair, at 90 degrees on the floor, and at 120 degrees on the floor. Only 37% of patients thought they could kneel, whereas 81% were actually able to kneel ( p<0.001). Ability to kneel on the chair and on the floor at 90 degrees was significantly better than perceived ability for all prosthesis types ( p<0.001). Kneeling at 120 degrees showed no difference between perception and reality except for the PFR group ( p<0.05). In all positions, increased range of movement significantly improved kneeling ability ( p<0.001). Kneeling ability in men was significantly better than in women ( p<0.001). Patient-centred questionnaires do not accurately document kneeling ability after knee arthroplasty.

Work-related musculoskeletal disorders: the epidemiologic evidence and the debate

The debate about work-relatedness of musculoskeletal disorders (MSDs) reflects both confusion about epidemiologic principles and gaps in the scientific literature. The physical ergonomic features of work frequently cited as risk factors for MSDs include rapid work pace and repetitive motion, forceful exertions, non-neutral body postures, and vibration. However, some still dispute the importance of these factors, especially relative to non-occupational causes. This paper addresses the controversy with reference to a major report recently commissioned by the US Congress from the National Research Council (NRC) and Institute of Medicine (IOM) (2001). The available epidemiologic evidence is substantial, but will benefit from more longitudinal data to better evaluate gaps in knowledge concerning latency of effect, natural history, prognosis, and potential for selection bias in the form of the healthy worker effect. While objective measures may be especially useful in establishing a more secure diagnosis, subjective measures better capture patient impact. Examination techniques still do not exist that can serve as a "gold standard" for many of the symptoms that are commonly reported in workplace studies. Finally, exposure assessment has too often been limited to crude indicators, such as job title. Worker self-report, investigator observation, and direct measurement each add to understanding but the lack of standardized exposure metrics limits ability to compare findings among studies. Despite these challenges, the epidemiologic literature on work-related MSDs-in combination with extensive laboratory evidence of pathomechanisms related to work stressors-is convincing to most. The NRC/IOM report concluded, and other reviewers internationally have concurred, that the etiologic importance of occupational ergonomic stressors for the occurrence of MSDs of the low back and upper extremities has been demonstrated.

Knee disorders in the general population and their relation to occupation

BACKGROUND

Hospital based studies of occupational risk factors for knee disorders are complicated by the possibility of selective referral to hospital of people whose work is made difficult by their symptoms.

AIMS

To explore the extent of such bias and to assess the association of meniscal injury with occupational activities.

METHODS

A questionnaire was mailed to a community sample of 2806 men aged 20-59 years in southern England. This asked about lifetime occupational and sporting activities, and any history of knee symptoms lasting 24 hours or longer. Rates of hospital referral were compared in symptomatic men according to their occupational activities. In a nested case-control investigation, the occupational activities of 67 men who reported meniscectomy were compared with those of 335 controls.

RESULTS

Among 1404 men who responded to the questionnaire, the lifetime prevalence of knee symptoms was 54%, and in 70% of cases the symptoms had started suddenly, usually while playing sport. Symptomatic men whose work entailed kneeling or squatting were more likely to be referred to an orthopaedic surgeon than the average (28% and 31% versus 24%), especially if they experienced locking of the knee (69% and 73% versus 43%). In the nested case-control study, meniscectomy was associated with playing soccer and work that involved regular kneeling or squatting.

CONCLUSIONS

Results suggest that hospital referral for knee symptoms is influenced to some extent by patients' occupational activities. Playing soccer is confirmed as a strong risk factor for knee cartilage injury.

Can knees kneel? Kneeling ability after total, unicompartmental and patellofemoral knee arthroplasty

This study investigates patients' perception of kneeling ability before and at 1 and 2 years after total, unicompartmental knee replacement (UKR) and patellofemoral knee replacement (PFR), for osteoarthritis. Kneeling is an important function of the knee joint required for many daily activities and inability to kneel after knee surgery is a frequent cause of dissatisfaction. Data were prospectively collected on 253 knees. A kneeling score was obtained by analysis of the relevant section of the Oxford knee score. Scores were obtained pre-operatively and at 1 and 2 years post-operatively. Absolute values and change following surgery were recorded. Correlations with pain and other knee functions were also made. Kneeling ability prior to surgery was poor in all 3 groups (80% found it extremely difficult or impossible to kneel) and improved in all groups after surgery (20% had little or no difficulty to kneel at 2 years). Kneeling ability was best in UKR and worst in PFR. These results suggest that kneeling ability in osteoarthritic patients is poor but improves with knee arthroplasty surgery, however the majority of patients will still have difficulty in kneeling.

Hip pain onset in relation to cumulative workplace and leisure time mechanical load: a population based case-control study

OBJECTIVE

In an unselected community sample of adults, to assess the role and importance of exposure to mechanical factors both at work and leisure in the aetiology of hip pain.

METHOD

A population based prevalence case-control study. Cases and controls were identified from a population survey of 3847 subjects registered with two general practices in Cheshire, United Kingdom. All subjects received a postal questionnaire which inquired about hip pain during the past month. An occupational history was obtained, including exposure to each of seven physical demands. Information was also obtained on history of participation in eight common sporting activities.

RESULTS

88% of those invited to participate returned a completed questionnaire. The 352 subjects with hip pain were designated as cases, and the remaining 3002 subjects as controls. In people ever employed, hip pain was significantly associated with high cumulative workplace exposure (before onset) of walking long distances over rough ground, lifting/moving heavy weights, sitting for prolonged periods, walking long distances, frequent jumping between different levels, and standing for prolonged periods. Odds ratios (ORs) in the higher exposure categories ranged from 1.46 to 2.65. Cumulative exposure to three sporting activities was significantly associated with hip pain: track and field sports, jogging, and walking, with odds ratios varying between 1.57 to 1.94. On multivariate analysis three factors were independent predictors of hip pain onset: cumulative exposure of sitting for prolonged periods (higher exposure v not exposed: OR=1.82, 95% confidence interval (CI) 1.13 to 2.92), lifting weights >50 lb (23 kg) (OR=1.74, 95% CI 1.06 to 2.86) (both relating to the workplace), and walking as a leisure activity (OR=1.97, 95% CI 1.32 to 2.94). The population attributable risk associated with each of these activities was 21%, 13%, and 16%, respectively

CONCLUSIONS

Cumulative exposure to some workplace and sporting "mechanical" risk factors for hip osteoarthritis (OA) appear to be related to hip pain in general-some (but not all) have previously been related to hip OA. Because these are common workplace or leisure time activities their attributable risk is high.

Symptoms of musculoskeletal disorders among apprentice construction workers

Musculoskeletal disorders (MSDs) are a major cause of work-related disability and lost-time illnesses for many occupational groups. This study determined the prevalence of musculoskeletal symptoms among young construction workers. A symptom and job factors survey was self-administered to 996 construction apprentices. Prevalence was determined by the percent of positive responses to musculoskeletal symptom questions. Odds ratios and 95 percent confidence intervals were the measures of association between prevalent musculoskeletal symptoms and demographic, leisure, and job factors and were determined by logistic regression. The low back was the site most commonly reported for job-related musculoskeletal symptoms (54.4%), which was also the most common reason for seeking care from a physician (16.8%) and missing work (7.3%). Number of years worked in the construction trade was significantly associated with knee (p-trend = 0.0009) and wrist/hand (p-trend < 0.04) MSD symptoms and was suggestive of an association with low back pain (p-trend = 0.05). "Working in the same position for long periods" was the job factor identified as most problematic, with 49.7 percent of all construction apprentices rating it as a moderate/major problem contributing to musculoskeletal symptoms. Musculoskeletal symptoms are a significant problem among young construction workers at the beginning of their careers. Prevention strategies are needed early in the apprentice training program to reduce the potential disability associated with work-related musculoskeletal symptom disorders.

Kneeling requirements and arthroplasty surgery

We investigated the physical characteristics and symptoms related to kneeling in a normal population. One hundred people were recruited at random. Of these, 27 subjects had knee pain and 73 were normal. Measurements were in kilograms with subjects on scales in three positions: standing, kneeling at 90 degrees and kneeling at full flexion. All 73 normal subjects could kneel at 90 degrees with an average of 94% of their body weight and at full flexion with an average of 51% of their body weight. The 27 subjects with knee pain were able to kneel at 90 degrees with an average of 97% of their body weight and in full flexion with an average of 50% of their body weight. Weight transmitted through the knees at full flexion is significantly less than when at 90 degrees whether subjects had pain or not. Future development of knee arthroplasty, when catering for kneeling might need to concentrate on achieving a better range of movement.

Physical workload and risk of early retirement: prospective population-based study among middle-aged men

Early retirement produces a heavy economic burden in many western societies. There is a need to identify single risk factors for early retirement and to find methods for preventing it. To estimate the effect of heavy physical work on early retiring, a cohort of 1755 men aged 42 to 65 years from eastern Finland was followed up from 1984 to 2000. Self-estimated physical workload was assessed at baseline. The inclusive pension records were obtained from national pension institutions. Logistic regression modeling was used to estimate the effect of physical workload and single physical risk factors on the risk of disability pension and nonillness-based pension. Risks were estimated for both disease-specific and all disability pensions. The interaction of physical fitness and physical workload and the resulting effects on risk were also estimated. During the follow-up, 861 (49.1%) men retired on a disability pension and 331 men (18.9%) retired on a nonillness-based early pension. Only 273 (15.6%) men reached the age for getting the normal old-age pension without having had any other early pension After adjustment for age, body mass index, alcohol consumption, smoking, maximal oxygen uptake, education and corresponding illness at baseline, heavy physical work was found to be associated with an increased risk of being retired on a disability pension due to musculoskeletal disorders (odds ratio (OR) 2.21, 95% confidence interval 1.36 to 3.61) but not due to cardiovascular or mental diseases. The association was stronger if cardiorespiratory fitness was poor. Lifting, static muscular loading and uncomfortable work positions increased the risk of early retirement especially due to musculoskeletal disorders. Loading of the upper extremity alone or with the neck and shoulder region seems to be an independent risk factor for early retirement. We concluded that physical workload increases the risk of retirement on a disability pension especially due to musculoskeletal disorders. In heavy physical work, the risk is increased especially among men with musculoskeletal or cardiovascular disease and poor cardiorespiratory fitness.

Risk factors for occupational knee related disability among enlisted women in the US Army

AIMS

To identify sociodemographic and occupational determinants of knee related disability discharge from the US Army among enlisted women, and to investigate effect modification.

METHODS

A case-control study of 692 cases of knee related disability discharge and 2080 incidence density matched controls nested within the population of all 244 000 enlisted women on active duty in the US Army, 1980-97. We used logistic regression to identify determinants of disability, stratified to explore effect modification by demographic and work characteristics.

RESULTS

The risk of disability discharge was twice as high (odds ratio (OR) 2.4, 95% confidence interval (CI): 1.71 to 3.47) for the oldest (33-60 years) versus the youngest (17-21 years) women. Non-whites had lower risk than whites (OR 0.5, 95% CI: 0.41 to 0.60), as did married (OR 0.7, 95% CI: 0.54 to 0.81) relative to non-married women. Those of lower rank (pay grades E1-E3) were at five times the risk of disability discharge compared to those of higher ranks (pay grades E4-E9, OR 5.0, 95% CI: 2.86 to 8.33), while ORs were highest for those with longer duration of service compared to women on active duty for a year or less (OR 1.4, 95% CI: 0.8 to 2.55 after 12 years). Race modified several effects, including that of rank. Age, duration of service, and pay grade were too highly correlated to draw firm conclusions about their independent modifying effects on risk of disability discharge from the Army.

CONCLUSIONS

Sociodemographic factors had larger effects than occupational characteristics on risk of knee related disability discharge from the US Army. Interactions suggest subgroups at differing risk levels that might be targeted for more detailed investigations.

A prospective study on knee pain and its risk factors

OBJECTIVES

To evaluate the effects of work-related and individual factors as well as physical activity and sports on the incidence and persistence of knee pain among a working population.

DESIGN

Employees of a large Finnish forestry company replied to a questionnaire (a modified version of the Nordic Questionnaire) on musculoskeletal pain and its possible risk factors at the baseline of this study. A cohort of 2122 workers free of knee pain and another cohort of 333 workers with severe knee pain were followed up for one year. The effects of the risk factors on the incidence and persistence of knee pain were studied using multivariable logistic regression models.

RESULTS

A total of 214 (10%) workers developed knee pain during the follow-up. Significant predictors of incident knee pain in the multivariable model were higher age, overweight, smoking, and previous knee injuries. Also, working with the trunk forward flexed in kneeling or standing position and physically strenuous work were non-significant predictors of incident knee pain. Of those 333 workers with severe knee pain at baseline, 220 (66%) still reported severe knee pain after one year. Higher age and job dissatisfaction increased the risk of persistent symptoms. General physical exercise and different sports activities did not predict the incidence or persistence of knee pain.

CONCLUSIONS

In this large prospective study, the risk factors for self-reported knee pain seemed to be highly similar to the risk factors for knee osteoarthritis (OA) reported in other papers. Age, previous knee injuries, overweight, and knee-straining work were those risk factors, which contributed to the incidence of knee pain. Psychosocial elements of work were more involved in the persistence of the symptoms in the knee.

Mechanical loads at the knee joint during deep flexion

There is a lack of fundamental information on the knee biomechanics in deep flexion beyond 90 degrees. In this study, mechanical loads during activities requiring deep flexion were quantified on normal knees from 19 subjects, and compared with those in walking and stair climbing. The deep flexion activities generate larger net quadriceps moments (6.9-13.5% body weight into height) and net posterior forces (58.3-67.8% body weight) than routine ambulatory activities. Moreover, the peak net moments and the net posterior forces were generated between 90 degrees and 150 degrees of flexion. The large moments and forces will result in high stress at high angles of flexion. These loads can influence pathological changes to the joint and are important considerations for reconstructive procedures of the knee. The posterior cruciate ligament should have a substantial role during deep flexion, since there was a large posterior load that must be sustained at the knee. The mechanics of the knee in deep flexion are likely a factor causing problems of posterior instability in current total knee arthroplasty. Thus, it is important to consider the magnitude of the loads at the knee in the treatment of patients that commonly perform deep flexion during activities of daily living.