Risk factors for knee replacement due to primary osteoarthritis, a population based, prospective cohort study of 315,495 individuals

Abstract

BackgroundOsteoarthritis (OA) of the knee is a common and disabling condition. We wanted to investigate the modifiable risk factors Body Mass Index (BMI) and physical activity, using knee replacement (KR) as a marker for severely symptomatic disease, focusing on the interaction between these risk factors.Methods315,495 participants (mean age 43.0 years) from national health screenings were followed prospectively with respect to KR identified by linkage to the Norwegian Arthroplasty Register. Data were analysed by Cox proportional hazard regression.ResultsDuring 12 years of follow up 1,323 individuals received KR for primary OA. There was a dose–response relationship between BMI and heavy labour, and later KR. Comparing the highest versus the lowest quarter of BMI, the relative risk was 6.2 (95% CI: 4.2-9.0) in men and 11.1 (95% CI: 7.8-15.6) in women. Men reporting intensive physical activity at work had a relative risk of 2.4 (95% CI: 1.8-3.2) versus men reporting sedentary activity at work, the corresponding figure in women being 2.3 (95% CI: 1.7-3.2). The effect of BMI and physical activity at work was additive. The heaviest men with the most strenuous work had a RR of 11.7 (95% CI: 5.9-23.1) compared to the ones with the lowest BMI and most sedentary work. For women the corresponding RR was 15.8 (95% CI: 8.2-30.3). There was no association between physical activity during leisure and KR.ConclusionWe found that a high BMI and intensive physical activity at work both contribute strongly to the risk of having a KR. As the two risk factors seem to act independently, people with strenuous physical work with a high BMI are at particularly high risk for severely disabling OA of the knee, and should be targeted with effective preventive measures.

The causal role of smoking on the risk of hip or knee replacement due to primary osteoarthritis: a Mendelian randomisation analysis of the HUNT study

“…Our data adds support to previous observational studies which have suggested a negative association between smoking and TJR [5][6][7] . In the Singapore Chinese Health Study current smokers compared with never smokers showed a dose-dependent inverse association between the numbers of cigarettes smoked and the risk of knee replacement 5 .…”

“…Similarly, after accounting for comorbidities and the competing risk of death, an Australian prospective cohort study found that current smokers were less likely to undergo a TJR than non-smokers 6 . Current smoking also reduced the likelihood of receiving TKR in a former Norwegian cohort study, however only among women 7 . There is no clear biological explanation for an inverse association between smoking and OA, but one theory is related to the upregulation of glycosaminoglycan and collagen synthetic activity of articular chondrocytes as a direct effect of nicotine, something which has been shown in vitro 9 .…”

“…Another potential explanation is the indirect effect of smoking on lifestyle factors such as BMI. Increasing BMI is an established risk factor for OA and subsequent TJR 26,27 and there is evidence to suggest that smoking may lead to lower BMI 18,28,29 , which could mediate the effect of smoking on TJR 30 . However, the association of rs1051730 T alleles with TJR was only slightly attenuated after statistical adjustment for BMI.…”

“…No curative treatment for OA is available, which places emphasis on identifying modifiable risk factors for disease prevention and treatment of early OA 2 . The results of observational studies suggest that smoking could have a protective effect on the development of OA 3,4 and subsequent hip and knee replacement [5][6][7] . Although results from in vitro data have indicated a beneficial effect of nicotine on chondrocyte function, the mechanisms remain unclear 8,9 .…”

Is There a Dose‐Response Relationship Between Weight Loss and Symptom Improvement in Persons With Knee Osteoarthritis?

“…As obesity is increasing in prevalence globally, particularly in the elderly, it is likely that more individuals will be affected by KOA in the future (4). Obesity is the leading risk factor for KOA incidence and, in addition, obesity contributes directly to the genesis of symptoms and to the need for joint replacement (5). This relationship is driven in part by increased mechanical load; a single kilogram of body weight causes 4 kg of knee joint compression with each step (6).…”