Hereditary and environmental factors causing total joint replacement due to hip and knee osteoarthritis – a twin registry based prospective cohort study

Karin Magnusson, Kåre Birger Hagen


The relative contribution of genetic factors and more modifiable environmental factors to a clinically
relevant osteoarthritis (OA) diagnosis is unkown. In this paper we present an ongoing study on the genetic
contribution to total joint replacement (TJR) due to hip and knee OA and effects of lifestyle and lifestyle
related conditions on TJR due to OA. We have linked data on incident OA from the Norwegian Arthroplasty
Registry were l with the Norwegian Twin Registry on the National ID number in 2014, thus obtaining a
population based cohort of same-sex twins born 1915-60. Data on height, weight and lifestyle were selfreporteded
in questionnaires conducted between 1978 and 1992. The monozygotic (MZ) and dizygotic
(DZ) concordances as well as the genetic contribution vs. contribution of more modifiable, environmental
factors to arthroplasty will be examined in separate analyses for the hip and the knee joint. The sample
comprised N=18058 twins (N=3803 MZ and N=5226 DZ pairs) including N=9650 (53.4%) females and a
mean (SD) age of 38 (12.3) years at questionnaire response. Some preliminary analyses have been performed
showing a higher concordance for TJR due to hip OA among MZ (0.36) than DZ twins (0.16), which may
be consistent with a genetic contribution to hip OA. TJR due to hip OA may be determined by genetic
factors. Results for the knee joint as well as final results from hereditary analyses and co-twin control
analyses of will be published consecutively from 2016.

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