title: Relationships between fatty infiltration in the thigh and calf in women with knee osteoarthritis.
abstract: BACKGROUND
  In individuals with knee osteoarthritis (OA), fatty infiltration into thigh muscle is associated with poor physical performance and strength. However, it is not known whether this also occurs in the calf and if this impacts physical function.
  
  
  OBJECTIVE
  We investigated the relationships between volumes of intramuscular fat (intraMF), intermuscular fat (IMF), subcutaneous fat (SCF), lean muscle and muscle adiposity, in the thighs compared to the calves of women with knee OA.
  
  
  METHODS
  MRI scans of the thigh and calf were acquired from 20 women over 55 years with knee OA (3.0T Discovery MR750, GE Healthcare). Axial IDEAL (iterative decomposition of water and fat with echo asymmetry and least-squares estimation) fat-separated images were segmented to quantify intraMF, IMF, SCF and lean muscle volumes (SliceOmatic 5.0, Tomovision). Correlation and linear regression analyses were run.
  
  
  RESULTS
  We found a positive relationship between thigh and calf intraMF (R2= 0.592; B = 5.49; p = 0.001), muscle adiposity (R2= 0.539; B = 0.567; p = 0.001), and SCF volume (R2= 0.699; B = 12.847; p = 0.001), controlling for waist-to-hip ratio. Relationships between thigh and calf IMF (R2= 0.239; B = 7.743; p = 0.061), lean muscle (R2= 0.245; B = 4.149; p = 0.047) and combined intraMF and IMF volume (R2= 0.242; B = 6.162; p = 0.044) were not significant.
  
  
  CONCLUSIONS
  Although a correlation exists between thigh and calf muscle adiposity, intraMF and SCF, this does not hold true for IMF or lean muscle. A greater amount of intraMF infiltration occurs in the thigh compared to the calf of women with knee OA.
  
  
  CONCLUSIONS
  The calf and thigh may both be involved in pathologic changes in muscle composition in knee OA.
authors.affiliation: Department of Medicine, McMaster University, 25 Charlton Ave. E., Suite 501, Hamilton, ON, L8N 1Y2, Canada.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Davison
authors.affiliation: School of Rehabilitation Science, McMaster University, Hamilton, Canada.
authors.forename: Monica R
authors.initials: MR
authors.lastname: Maly
authors.affiliation: Department of Medicine, McMaster University, 25 Charlton Ave. E., Suite 501, Hamilton, ON, L8N 1Y2, Canada.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Adachi
authors.affiliation: Department of Electrical and Computer Engineering, McMaster School of Biomedical Engineering, McMaster University, Hamilton, Canada.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Noseworthy
authors.affiliation: Department of Medicine, McMaster University, 25 Charlton Ave. E., Suite 501, Hamilton, ON, L8N 1Y2, Canada. beattik@mcmaster.ca.
authors.forename: Karen A
authors.initials: KA
authors.lastname: Beattie
mesh_terms: D000273:Adipose Tissue / Q000473:pathology*; D000368:Aged; D001823:Body Composition; D005260:Female; D006801:Humans; D007866:Leg / Q000000981:diagnostic imaging / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods; D008875:Middle Aged; D009765:Obesity / Q000503:physiopathology; D020370:Osteoarthritis, Knee / Q000473:pathology / Q000503:physiopathology; D052097:Quadriceps Muscle / Q000000981:diagnostic imaging / Q000473:pathology; D013223:Statistics as Topic; D013848:Thigh / Q000000981:diagnostic imaging / Q000473:pathology
keywords: Adipose tissue; Knee; Magnetic resonance imaging; Osteoarthritis; Women