There is good evidence that occupations involving frequent kneeling and squatting significantly increase the risk of knee OA. OA in miners and carpet and floor layers are both prescribed diseases, the former related to both kneeling and squatting while working in low seams, the latter from prolonged loading of the knee through kneeling(IIAC, 2008, IIAC, 2010). Heavy manual work particularly including heavy lifting and carrying and stair climbing increases the risk of knee OA, and professional elite sportsmen are at increased risk. Some of this increased risk is due to injury, but some appears to be directly caused by the work itself.
An increased risk of knee OA has been identified for occupations that include elite sports, heavy manual work, kneeling, squatting, lifting and carrying, and climbing stairs. A systematic review of observational studies of knee OA and occupation attempted to quantify the risk of knee OA for specific occupations and occupational activities. Studies included a total of over half a million cases and a variety of occupational exposures including kneeling, lifting, carrying, -squatting or other knee-bending activities. Elite sports have been shown to be high risk as have been floor layers. No risk was noted from standing work. (see table below) (McWilliams et al., 2011)
|
Occupational activities |
No. of subjects |
Heterogeneity (p) |
risk estimate |
|
|
Heavy or manual work |
546,853 |
80.9 (<0.0001) |
1.45 (1.20–1.76) |
|
|
Elite sports |
9,703 |
55.9 (0.08579) |
1.72 (1.35–2.20) |
|
|
Kneeling |
9,236 |
68.2 (0.0009) |
1.30 (1.03–1.63) |
|
|
Squatting |
13,181 |
25.5 (0.2013) |
1.40 (1.21–1.61) |
|
|
Lifting/carrying |
11,833 |
77.7 (<0.0001) |
1.58 (1.28–1.94) |
|
|
Climbing stairs |
16,253 |
72.5 (<0.0001) |
1.29 (1.08–1.55) |
|
|
Standing work |
7,896 |
80.8 (<0.0001) |
1.11 (0.81–1.51) |
|
|
Knee bending/straining |
262,073 |
72.1 (0.0007) |
1.60 (1.15–2.21) |
|
Kneeling, squatting, lifting and climbing can cause and/or aggravate knee OA. A systematic search for articles from 1996 to 2011 showed reasonably good evidence that physical work activities (especially kneeling, squatting, lifting and climbing) can cause and/or aggravate knee OA. Obese workers with such exposures are at additional risk of knee OA and should particularly be encouraged to lose weight (Palmer, 2012).
Floor layers, bricklayers and occupations with heavy physical workload present a strong risk of knee OA in men and women. A follow-up study based on register data of the whole Danish population from 1981 to 2006 found a strong risk for knee OA in occupations with heavy physical workload, in particular male floor layers and bricklayers and male and female healthcare assistants. The risk increased with cumulative years in the occupation in both men and women (Andersen et al., 2012).
ANDERSEN, S., THYGESEN, L. C., DAVIDSEN, M. & HELWEG-LARSEN, K. 2012. Cumulative years in occupation and the risk of hip or knee osteoarthritis in men and women: a register-based follow-up study. Occup Environ Med, 69, 325-30.
IIAC 2008. Osteoarthritis of the knee in coal miners. Command Paper 7440: Department for Work and Pensions.
IIAC 2010. Osteoarthritis of the knee in carpet fitters and carpet and floor layers. Command Paper 7964: Department for Work and Pensions.
MCWILLIAMS, D. F., LEEB, B. F., MUTHURI, S. G., DOHERTY, M. & ZHANG, W. 2011. Occupational risk factors for osteoarthritis of the knee: a meta-analysis. Osteoarthritis Cartilage, 19, 829-39.
PALMER, K. T. 2012. Occupational activities and osteoarthritis of the knee. Br Med Bull, 102, 147-70.