title: High levels of fat and (n-6) fatty acids in cancellous bone in osteoarthritis.
abstract: BACKGROUND
  Osteoarthritis (OA) is strongly linked with obesity and patients with osteoporosis (OP) have a low body mass index. Anecdotal evidence, clinical and laboratory, suggests that OA bone contains more fat. However, conversion of osteoblasts to adipocytes is reported in OP and this would suggest that the more porous OP cancellous bone would have a high fat content.
  
  
  OBJECTIVE
  To test the hypothesis that OA bone contains more fat than OP bone.
  
  
  METHODS
  Cores of cancellous bone were obtained from femoral heads of patients undergoing surgery for either OA or OP. Lipids were extracted using chloroform-methanol, weighed and expressed as a fraction of core mass and volume. A fatty acid analysis was performed using gas chromatography.
  
  
  RESULTS
  OA bone contained twice as much fat per unit volume of tissue as OP. Levels of n-6 fatty acids were elevated in OA, especially arachidonic acid (C20:4 n-6) which was almost double that found in OP.
  
  
  CONCLUSIONS
  These data support the hypothesis that lipids may play a significant role in the pathogenesis of OA and may provide part of the key to understanding why OA and OP lie at opposite ends of the spectrum of bone masses.
authors.affiliation: Department of Orthopaedics, University of Aberdeen, Institute of Medical Sciences, Foresterhill, Aberdeen, AB25 2ZD. m.plumb@abdn.ac.uk
authors.forename: Mandy S
authors.initials: MS
authors.lastname: Plumb
authors.forename: Richard M
authors.initials: RM
authors.lastname: Aspden