Background/Purpose: Knee osteoarthritis (OA) is increasingly diagnosed in younger adults, likely due to accumulation of risk factors such as obesity, knee injury, occupational exposure and family history. This shift in the age of the OA population suggests that prevention efforts should focus on younger individuals. However, knowledge of the disease and perceptions of risk among younger people have not been investigated formally.

Methods: We recruited a population-based cohort 25-45 years of age with no history of knee OA using Amazon’s Mechanical Turk, an online marketplace used extensively for behavioral research. After collecting demographic and risk factor information, we asked participants to estimate their 10-year and lifetime risk of knee OA. We compared perceived risk with ‘actual’ risk derived from the OA risk calculator (OARC). OARC is an online tool built on the basis of the validated OA Policy Model. OARC matches user inputs to corresponding model outputs that include 10-year and lifetime risk of diagnosed symptomatic knee OA based on age, sex, race, obesity status, family history of OA, history of knee injury, and occupational risks. Increases in OA risk were quantified using published literature. 

Results: 375 people completed the study. Mean age was 32 years; 52% were females; 21% identified as non-white; 56% had a college degree. Study participants resided in all regions of the US: 17% — Northest, 18% — Midwest, 38% — South and 27% — West. 70% reported family history of OA, 20% reported a history of knee injury, and 48% reported occupational exposure. 11% reported having 3+ risk factors for OA, 24% reported two risk factors, and 35% reported one risk factor. Using the OARC, we estimated a mean lifetime OA risk of 25% for this sample and 10-year risk of 4%. Participants estimated their lifetime and 10-year OA risk at 48% and 26%, respectively. 15% estimated their lifetime OA risk within 25% of the lifetime risk determined by the risk calculator. 61% overestimated their lifetime risk by at least 50%, while 16% underestimated their lifetime risk by at least 25%. 46% overestimated their lifetime risk of knee OA at least 2 fold, and 20% overestimated their risk 3 fold. 75% of study participants overestimated their 10 year risk by at least 2 fold and 66% by 3 fold. We found that obesity, female sex, family history of OA, history of knee injury, and occupational exposure were all significantly associated with greater perceived lifetime risk of OA.

Conclusion: Risk factors are prevalent in this relatively young cohort and subjects with risk factors perceived their risk as higher than those without risk factors. However, participants consistently overestimated their lifetime risk and showed even greater overestimation of their 10-year risk, suggesting a lack of knowledge about the timing of OA onset. Family history in particular was associated with overestimation of OA risk. Family members of OA patients may perceive knee OA as inevitable, while its contribution to the risk of knee OA has been shown to be considerably less than contribution of obesity and injury. These data offer insights for awareness and risk interventions among younger persons at risk for knee OA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/risk-and-risk-perception-of-knee-osteoarthritis-in-the-us-population-based-study/