title: Low bone mineral density is associated with reduced hip joint space width in women: results from the Copenhagen Osteoarthritis Study.
abstract: OBJECTIVE
  Since estrogen receptors (ER-alpha/ER-beta) were identified in human chondrocytes, animal and experimental studies have demonstrated the importance of continued estrogen production for the integrity of articular cartilage. However, human epidemiological support of the hypothesis has been inconclusive. The present cross-sectional study investigated the relationship between reduced bone mineral density (BMD), as a surrogate parameter of endogenous estrogen status assessed by digital x-ray radiogrammetry, and reduced minimum hip joint space width (JSW).
  
  
  METHODS
  Standardized hand radiographs of the Copenhagen Osteoarthritis Study cohort of 3,913 adults (1,470 male/2,443 female) with a mean age of 60 years (range, 18-92) were analyzed using X-Posure digital software, version 2.0 (Sectra-Pronosco). The system is operator independent. From 1,200 individual measurements per radiograph, mean BMD was calculated. Minimum hip JSW was assessed on standardized pelvic radiographs.
  
  
  RESULTS
  Digital x-ray radiogrammetry BMD decreased in both men and women after the age of 45 years, progressively more so in women. Although minimum hip JSW in men remained relatively unaltered throughout life, a marked decline in female minimum hip JSW after age 45 years was observed. We found moderate but highly significant relationships between reduced BMD and reduced hip JSW in women (P < 0.0001), adjusted for age and dysplastic joint incongruity.
  
  
  CONCLUSIONS
  We believe that the present study supports the hypothetical relationship between reduced estrogen levels and hip JSW reduction in women.
authors.affiliation: Department of Orthopaedic Surgery, Copenhagen University Hospital of Hvidovre, Hvidovre, Denmark. sjac@dadlnet.dk
authors.forename: Steffen
authors.initials: S
authors.lastname: Jacobsen
authors.forename: Trine W
authors.initials: TW
authors.lastname: Jensen
authors.forename: Pernille
authors.initials: P
authors.lastname: Bach-Mortensen
authors.forename: Lars
authors.initials: L
authors.lastname: Hyldstrup
authors.forename: Stig
authors.initials: S
authors.lastname: Sonne-Holm
mesh_terms: D015502:Absorptiometry, Photon; D017677:Age Distribution; D015519:Bone Density; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006621:Hip Joint / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D008593:Menopause; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000000981:diagnostic imaging* / Q000453:epidemiology / Q000209:etiology / Q000473:pathology; D012720:Severity of Illness Index; D012737:Sex Factors