Association between occupation and knee and hip replacement due to osteoarthritis: a case-control study

The following is the case-control study design. All patients still living in Iceland who had had a TKR or THR due to OA as of the end of 2002 were invited to participate. First degree relatives of participating patients served as controls. N = 1,408 cases (832 women) and n = 1,082 controls (592 women), 60 years or older and who had adequately answered a questionnaire were analyzed. Occupations were classified according to international standards. Inheritance of occupations was calculated by using the Icelandic Genealogy Database.The age adjusted odds ratio (OR) for male farmers getting a TKR due to OA was 5.1 (95% confidence interval (CI) 2.1 to 12.4) and for a male farmer getting a THR due to OA the OR was 3.6 (95% CI 2.1 to 6.2). The OR for a fisherman getting a TKR was 3.3 (95% CI 1.3 to 8.4). No other occupations showed increased risk for men. For women there was no increased risk for any occupation. Farming and fishing were also the occupations that showed the greatest degree of inheritance.These results support an association in males between occupations with heavy physical load and both TKR and THR for OA.There are several possible risk factors for osteoarthritis (OA) of the knee and hip. Body mass index (BMI) is well established as a risk factor for both hip and knee OA for both genders [1,2]. It has been shown that high BMI precedes knee OA and thus causality can be assumed [3,4]. Occupation is another risk factor that has been linked to OA. Studies have varied in their design, in both definition of OA and exposure to workload. Most of the higher quality studies have based their definition on radiographic OA [5-9] or the case population has been individuals that are waiting for [10,11] or have received [12-17] a joint prosthesis. From a clinical standpoint, studies based on radiographic OA are less relevant, as there is poor correlation between radiographic OA and symptoms [18,19]. Exposure has either been defined from job titles [7,8,13,17] or exposure to