Knee osteoarthritis: influence of work involving heavy lifting, kneeling, climbing stairs or ladders, or kneeling/squatting combined with heavy lifting.

The purpose of the study was to evaluate the evidence for an association between knee osteoarthritis (kneeOA) and physical work demands. Systematic searches were made, and epidemiological studies on kneeOA and heavy lifting, kneeling and climbing stairs published in 1966 to 2007 inclusive were reviewed. The quality of the studies was assessed and an overall evaluation of the degree of evidence of a causal relationship between kneeOA and physically demanding work was made, using specific criteria of the different degrees of evidence of causality. Limitations of the studies include few participants, use of different diagnostic criteria and a poor description of the exposure. It is concluded that moderate evidence was found for a relationship between kneeling, heavy lifting and kneeOA. For the combination of kneeling/squatting and heavy lifting the association seemed stronger than for kneeling/squatting or heavy lifting alone, but only a few studies were found concerning this relationship. Therefore the degree of evidence for a causal relationship was considered to be moderate. In the studies on the association between kneeOA and climbing stairs or ladders, there was an increased risk for kneeOA, but only a few studies were found and no dose-response relationship has been investigated. The evidence of a causal relationship is therefore considered to be limited.