title: Risk and risk perception of knee osteoarthritis in the US: a population-based study.
abstract: OBJECTIVE
  We sought to investigate risk perception among an online cohort of younger US adults compared with calculated risk estimates.
  
  
  METHODS
  We recruited a population-based cohort 25-44 years of age with no history of knee osteoarthritis (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 risk derived from the OA risk calculator (OA Risk C), an online tool built on the basis of the validated OA Policy Model.
  
  
  RESULTS
  375 people completed the study. 21% reported having 3+ risk factors for OA, 25% reported two risk factors, and 32% reported one risk factor. Using the OA Risk C, we calculated a mean lifetime OA risk of 25% and 10-year risk of 4% for this sample. Participants overestimated their lifetime and 10-year OA risk at 48% and 26%, respectively. 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.
  
  
  CONCLUSIONS
  Risk factors are prevalent in this relatively young cohort. 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. These data offer insights for awareness and risk interventions among younger persons at risk for knee OA.
authors.affiliation: Orthopedic and Arthritis Center for Outcomes Research, Department of Orthopedic Surgery, Brigham and Women's Hospital, Boston, MA, USA. Electronic address: griffinmichl@gmail.com.
authors.forename: G L
authors.initials: GL
authors.lastname: Michl
authors.affiliation: Orthopedic and Arthritis Center for Outcomes Research, Department of Orthopedic Surgery, Brigham and Women's Hospital, Boston, MA, USA; Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA. Electronic address: jnkatz@partners.org.
authors.forename: J N
authors.initials: JN
authors.lastname: Katz
authors.affiliation: Orthopedic and Arthritis Center for Outcomes Research, Department of Orthopedic Surgery, Brigham and Women's Hospital, Boston, MA, USA; Division of Rheumatology, Immunology and Allergy, Brigham and Women's Hospital, Boston, MA, USA; Harvard Medical School, Boston, MA, USA. Electronic address: elosina@partners.org.
authors.forename: E
authors.initials: E
authors.lastname: Losina
mesh_terms: D000328:Adult; D015331:Cohort Studies; D005260:Female; D007722:Health Knowledge, Attitudes, Practice; D006801:Humans; D008297:Male; D020370:Osteoarthritis, Knee / Q000453:epidemiology / Q000209:etiology* / Q000523:psychology; D018570:Risk Assessment / Q000379:methods / Q000706:statistics & numerical data; D012307:Risk Factors; D014481:United States / Q000453:epidemiology
keywords: Behavior; Osteoarthritis; Risk calculator; Risk perception