title: State of the evidence.
abstract: OBJECTIVE
  This review focuses on recent studies of osteoarthritis epidemiology, including research on prevalence, incidence, and a broad array of potential risk factors at the person level and joint level.
  
  
  RESULTS
  Studies continue to illustrate the high impact of osteoarthritis worldwide, with increasing incidence. Person-level risk factors with strong evidence regarding osteoarthritis incidence and/or progression include age, sex, socioeconomic status, family history, and obesity. Joint-level risk factors with strong evidence for incident osteoarthritis risk include injury and occupational joint loading; the associations of injury and joint alignment with osteoarthritis progression are compelling. Moderate levels of physical activity have not been linked to increased osteoarthritis risk. Some topics of high recent interest or emerging evidence for association with osteoarthritis include metabolic pathways, vitamins, joint shape, bone density, limb length inequality, muscle strength and mass, and early structural damage.
  
  
  CONCLUSIONS
  Osteoarthritis is a complex, multifactorial disease, and there is still much to learn regarding mechanisms underlying incidence and progression. However, there are several known modifiable and preventable risk factors, including obesity and joint injury; efforts to mitigate these risks can help to lessen the impact of osteoarthritis.
authors.affiliation: aThurston Arthritis Research Center bDepartment of Medicine, University of North Carolina at Chapel Hill, Chapel Hill cDepartment of Veterans Affairs Medical Center, Center for Health Services Research in Primary Care, Durham dDepartment of Epidemiology eInjury Prevention Research Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
authors.forename: Kelli D
authors.initials: KD
authors.lastname: Allen
authors.forename: Yvonne M
authors.initials: YM
authors.lastname: Golightly
mesh_terms: D018450:Disease Progression; D014943:Global Health; D006801:Humans; D009017:Morbidity / Q000639:trends; D010003:Osteoarthritis / Q000453:epidemiology*