title: Genetic influences on osteoarthritis in women: a twin study.
abstract: OBJECTIVE
  To assess the relative contribution of genetic and environmental factors to common forms of osteoarthritis of the hands and knees.
  
  
  METHODS
  Classic twin study with unselected twins who were screened radiologically for osteoarthritis.
  
  
  METHODS
  130 identical and 120 non-identical female twins aged 48-70 recruited from a London based twin register and through a national media campaign.
  
  
  METHODS
  Similarity in identical compared with non-identical twin pairs for radiographic changes at the interphalangeal and first carpometacarpal joints of the hands and the tibiofemoral joint and patellofemoral joint of the knee expressed as intraclass correlations.
  
  
  RESULTS
  The intraclass correlations of radiographic osteophytes and narrowing at most sites and the presence of Heberden's nodes and knee pain were higher in the identical pairs. The intraclass correlation of the total radiographic osteoarthritis score in identical pairs (rMZ) was 0.64 (SE 0.05) compared with 0.38 (0.08) in non-identical pairs. The proportion of genetic variance of total osteoarthritis score (osteophytes and narrowing) with modelling techniques was estimated at 0.54 (95% confidence interval 0.43 to 0.65) and ranged from 0.39 to 0.65 for different sites and features (p < 0.001) after adjustment for age and weight.
  
  
  CONCLUSIONS
  These results demonstrate for the first time a clear genetic effect for radiographic osteoarthritis of the hand and knee in women, with a genetic influence ranging from 39-65%, independent of known environmental or demographic confounders. The results of this study should lead to further work on isolating the gene or genes involved in the pathogenesis of the common disabling disease.
authors.affiliation: Department of Rheumatology, St Thomas's Hospital, London.
authors.forename: T D
authors.initials: TD
authors.lastname: Spector
authors.forename: F
authors.initials: F
authors.lastname: Cicuttini
authors.forename: J
authors.initials: J
authors.lastname: Baker
authors.forename: J
authors.initials: J
authors.lastname: Loughlin
authors.forename: D
authors.initials: D
authors.lastname: Hart
mesh_terms: D000368:Aged; D004200:Diseases in Twins; D004777:Environment; D005260:Female; D006225:Hand / Q000000981:diagnostic imaging; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging; D008875:Middle Aged; D010003:Osteoarthritis / Q000000981:diagnostic imaging / Q000235:genetics*; D011859:Radiography; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic