title: Volumetric bone mineral density of the tibia is not increased in subjects with radiographic knee osteoarthritis.
abstract: OBJECTIVE
  Radiographic osteoarthritis (ROA) has previously been shown to be associated with an increase in areal bone mineral density (BMD) as assessed by dual energy X-ray absorptiometry (DXA). Here we have assessed volumetric bone density, size and strength by peripheral quantitative computed tomography (pQCT) in a large population-based cohort study in which knee radiographs were available.
  
  
  METHODS
  Two hundred and ninety-five men and 288 women from the MRC Hertfordshire Cohort Study underwent weight bearing extended knee X-rays and bone density measurement of the ipsi-lateral knee using pQCT.
  
  
  RESULTS
  Increasing radiographic grade in men but not women was associated with an increase in tibial total area at 38% site and cortical area at 14% site, but not with volumetric BMD. The tibial fracture loads as well as tibial polar strength strain index at 38% site were also increased. There were no significant associations of tibia bone area, BMD or strength with radiographic grade in women.
  
  
  CONCLUSIONS
  ROA is not associated with an increase in volumetric BMD as assessed by pQCT. It is, however, associated with a significant increase in bone area and strength, indicating that the association between ROA and areal BMD is mediated through bone size rather than volumetric BMD.
authors.affiliation: MRC Epidemiology Resource Centre, Southampton, United Kingdom. maysamabdin@hotmail.com
authors.forename: M
authors.initials: M
authors.lastname: Abdin-Mohamed
authors.forename: K
authors.initials: K
authors.lastname: Jameson
authors.forename: E M
authors.initials: EM
authors.lastname: Dennison
authors.forename: C
authors.initials: C
authors.lastname: Cooper
authors.forename: N K
authors.initials: NK
authors.lastname: Arden
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D015519:Bone Density / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000503:physiopathology*; D013977:Tibia / Q000000981:diagnostic imaging / Q000503:physiopathology*; D014057:Tomography, X-Ray Computed