title: Relationship of intermuscular fat volume in the thigh with knee extensor strength and physical performance in women at risk of or with knee osteoarthritis.
abstract: OBJECTIVE
  To determine the extent to which thigh intermuscular fat (IMF) and quadriceps muscle (QM) volumes explained variance in knee extensor strength and physical performance in women with radiographic knee osteoarthritis (ROA) and without.
  
  
  METHODS
  Baseline data from 125 women (age ≥50 years) in the Osteoarthritis Initiative study, with or at risk of knee ROA were included. Knee extensor strength was measured using a fixed force transducer, normalized to body mass (N/kg). Physical performance was the time required for 5 repeated chair stands (seconds). The IMF and QM volumes, normalized to height (cm(3) /meter), were yielded from analyses of T1-weighted axial magnetic resonance images of the midthigh. Mean IMF and QM volumes, extensor strength, and physical performance were compared between women with and without ROA, controlling for age. Hierarchical multiple regressions determined whether IMF and QM volumes were related to strength and performance after controlling for age, ROA status (yes/no), alignment, and pain.
  
  
  RESULTS
  Compared to subjects with ROA, the subjects without ROA were stronger and performed chair stands faster (P < 0.05). After adjusting for age, those subjects without ROA had less mean ± SD IMF (61.1 ± 20.3 cm(3) /meter) compared to mean ± SD ROA (72.0 ± 25.0 cm(3) /meter; P < 0.05). In the entire sample, 21.1% of variance in knee extensor strength was explained by alignment, pain, and IMF. A model explaining 13.4% of variance in physical performance included OA status and IMF. QM volume was unrelated to strength and physical performance.
  
  
  CONCLUSIONS
  IMF volume explained a small amount of variance in knee extensor strength and physical performance among women with or at risk of knee ROA.
authors.affiliation: Institute for Applied Health Sciences, Hamilton, Ontario, Canada. mmaly@mcmaster.ca
authors.forename: Monica R
authors.initials: MR
authors.lastname: Maly
authors.forename: Kristina M
authors.initials: KM
authors.lastname: Calder
authors.forename: Norma J
authors.initials: NJ
authors.lastname: Macintyre
authors.forename: Karen A
authors.initials: KA
authors.lastname: Beattie
mesh_terms: D050154:Adiposity / Q000502:physiology*; D000368:Aged; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007719:Knee Joint; D008137:Longitudinal Studies; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000502:physiology*; D020370:Osteoarthritis, Knee / Q000503:physiopathology*; D012307:Risk Factors; D013848:Thigh