To What Extent Is Severe Osteoarthritis Preventable?

Occupational and Non-Occupational Risk Factors for Knee and Hip Osteoarthritis

Tea Kontio; Markku Heliövaara; Eira Viikari-Juntura; Svetlana Solovieva

Disclosures

Rheumatology. 2020;59(12):3869-3877. 

In This Article

Abstract and Introduction

Abstract

Objectives: To explore the relative contribution of cumulative physical workload, sociodemographic and lifestyle factors, as well as prior injury to hospitalization due to knee and hip OA.

Methods: We examined a nationally representative sample of persons aged 30–59 years, who participated in a comprehensive health examination (the Health 2000 Study). A total of 4642 participants were followed from mid-2000 to end-2015 for the first hospitalization due to knee or hip OA using the National Hospital Discharge Register. We examined the association of possible risk factors with the outcome using a competing risk regression model (death was treated as competing risk) and calculated population attributable fractions for statistically significant risk factors.

Results: Baseline age and BMI as well as injury were associated with the risk of first hospitalization due to knee and hip OA. Composite cumulative workload was associated with a dose–response pattern with hospitalizations due to knee OA and with hospitalizations due to hip OA at a younger age only. Altogether, prior injury, high BMI and intermediate to high composite cumulative workload accounted for 70% of hospitalizations due to knee OA. High BMI alone accounted for 61% and prior injury only for 6% of hospitalizations due to hip OA.

Conclusion: Our results suggest that overweight/obesity, prior injury and cumulative physical workload are the most important modifiable risk factors that need to be targeted in the prevention of knee OA leading to hospitalization. A substantial proportion of hospitalizations due to hip OA can be reduced by controlling excess body weight.

Introduction

OA is the most common joint disorder in the world, and increases rapidly with age.[1] It is characterized by loss of joint cartilage, which leads to pain and functional limitations predominantly in the knees and hips.[2] Trends in years lived with disabilities due to OA showed a 46% increase from 1990 to 2016. Indeed, OA is the second most rapidly rising condition associated with disability, just behind diabetes, with a 52% increase in years lived with disabilities.[3]

About 20% of people aged 60 years and above report moderate to severe knee or hip pain and disability, and either would be considered in need of joint replacement or have already undergone surgery.[1,4] Previously identified modifiable risk factors for knee and hip OA comprise injury,[5–7] obesity,[6,8–11] occupational activities involving heavy physical work, heavy lifting, and co-occurrence of kneeling, squatting and bending.[12] Meta-analyses synthesizing evidence from a limited number of studies found moderate-quality evidence for an association between cumulative exposure to kneeling or squatting at work and knee OA[13] and a dose–response association between heavy lifting and hip OA in men.[14]

With the ageing population and prolongation of working life, a large increase in the prevalence of disabling OA is to be expected, imposing a high burden on health care services.[3] Although modifiable risk factors of OA are known, evidence for the prevention potential of targeting these factors is limited.[15,16] The importance of a risk factor for the prevention of a health outcome can be assessed by the population attributable fraction (PAF). PAF allows an estimation of the proportion of cases of a health outcome in the population that could be avoided if the risk factor of interest was removed.

The PAF estimates for knee and hip OA vary. According to a systematic review and meta-analysis, 5% of new cases of knee pain in adults >50 years of age were attributed to knee injury.[6] PAF associated with excess body weight varied between 8 and 60%, depending on the prevalence of overweight/obesity and the severity of knee OA.[6,15] The largest PAFs were observed for severe symptomatic knee OA awaiting total joint replacement and the smallest for asymptomatic radiographic knee OA.[15] Studies in earlier 1990s estimating aetiological fractions suggested that 20–40% of hip OA might result from physically demanding occupations.[17,18] Recently, we showed that at least 50% of disability retirement due to knee OA (both genders) and at least 40% of disability retirement due to hip OA (men) among individuals in physically heavy occupations could be attributed to physical work load factors.[18,19] A more comprehensive approach to the potential of targeting modifiable occupational and non-occupational risk factors for the prevention of disabling OA are warranted.

The aims of this study were to assess the relative contribution of cumulative physical workload, sociodemographic and lifestyle factors, as well as prior injury to hospitalization due to knee and hip OA and to calculate population attributable fractions for significant risk factors.

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