title: The association between parity and knee cartilage in young women.
abstract: OBJECTIVE
  There have been no reported studies of the association between parity and cartilage in young individuals. The aim of this study was to describe the association between parity, cartilage volume and cartilage defects in women aged 31-41 years.
  
  
  METHODS
  Cross-sectional study of 144 women, mean age 36 years and BMI 25 kg/m(2), who were participants in an established prospective study. Parity was assessed using a questionnaire. Knee (medial tibial, lateral tibial and patellar) cartilage volume, cartilage defects (grade 0-4 depending on the severity of cartilage thickness loss at tibial and patellar sites) and tibial bone area were assessed using T1-weighted fat-suppressed MRI.
  
  
  RESULTS
  The prevalence of cartilage defects (grade ≥2) in this population was 13%. Parity was associated with a higher risk of cartilage defects at the patellar [prevalence ratio (PR) per birth 1.52, 95% CI 1.05, 2.21; PR parous vs nulliparous 1.93, 95% CI 0.66, 5.65], but not tibial sites, after adjustment for confounders including age, BMI, smoking, physical activity, knee injury and tibial bone area. This association between parity and patellar cartilage defects was stronger for those women who had three or more births (vs nulliparous, PR 5.27, 95% CI 1.39, 20.01). There were no significant associations between parity and cartilage volume.
  
  
  CONCLUSIONS
  Parity was associated with knee cartilage defects primarily at the patellar site in this sample of young women. This association was more apparent with increasing number of live births, suggesting a possible adverse effect of parity on knee cartilage.
authors.affiliation: Menzies Research Institute Tasmania, 17 Liverpool Street, Hobart, Tasmania 7001, Australia.
authors.forename: Shuying
authors.initials: S
authors.lastname: Wei
authors.forename: Graeme
authors.initials: G
authors.lastname: Jones
authors.forename: Alison
authors.initials: A
authors.lastname: Venn
authors.forename: Flavia
authors.initials: F
authors.lastname: Cicuttini
authors.forename: Lyn
authors.initials: L
authors.lastname: March
authors.forename: Petr
authors.initials: P
authors.lastname: Otahal
authors.forename: Marita
authors.initials: M
authors.lastname: Cross
authors.forename: Marita
authors.initials: M
authors.lastname: Dalton
authors.forename: Terry
authors.initials: T
authors.lastname: Dwyer
authors.forename: Changhai
authors.initials: C
authors.lastname: Ding
mesh_terms: D000328:Adult; D002357:Cartilage Diseases / Q000209:etiology / Q000473:pathology*; D002358:Cartilage, Articular / Q000473:pathology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D010298:Parity / Q000502:physiology*; D011247:Pregnancy; D011446:Prospective Studies