title: Lean muscle volume of the thigh has a stronger relationship with muscle power than muscle strength in women with knee osteoarthritis.
abstract: BACKGROUND
  Thigh lean muscle and intramuscular fat have been implicated in the impairment of physical function observed in people with knee osteoarthritis. We investigated the relationships of quadriceps and hamstrings intramuscular fat fraction and lean muscle volume with muscle power and strength, controlling for neuromuscular activation, and physical performance in women with knee OA.
  
  
  METHODS
  Women (n=20) 55years or older with symptomatic, radiographic knee osteoarthritis underwent a 3.0T magnetic resonance imaging scan of the thigh of their most symptomatic knee. Axial fat-separated images were analyzed using software to quantify intramuscular fat and lean muscle volumes of the quadriceps and hamstrings. To quantify strength and power of the knee extensors and flexors, participants performed maximum voluntary isometric contraction and isotonic knee extensions and flexions, respectively. Electromyography of the quadriceps and hamstrings was measured. Participants also completed five physical performance tests.
  
  
  RESULTS
  Quadriceps and hamstrings lean muscle volumes were related to isotonic knee extensor (B=0.624; p=0.017) and flexor (B=1.518; p=0.032) power, but not knee extensor (B=0.001; p=0.615) or flexor (B=0.001; p=0.564) isometric strength. Intramuscular fat fractions were not related to isotonic knee extensor or flexor power, nor isometric strength. No relationships were found between intramuscular fat or lean muscle volume and physical performance.
  
  
  CONCLUSIONS
  Muscle power may be more sensitive than strength to lean muscle mass in women with knee osteoarthritis. Thigh lean muscle mass, but neither intramuscular nor intermuscular fat, is related to knee extensor and flexor power in women with knee osteoarthritis.
authors.affiliation: Department of Medicine, McMaster University, 501-25 Charlton Ave. East, Hamilton, ON L8N 1Y9, Canada. Electronic address: m_davison@hotmail.com.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Davison
authors.affiliation: School of Rehabilitation Science, McMaster University, Institute for Applied Health Sciences, Room 403, 1400 Main St. W. Hamilton, ON L8S 1C7, Canada; Department of Kinesiology, B.C. Matthews Hall, University of Waterloo, 200 University Ave. West, Waterloo, ON N2L 3G1, Canada. Electronic address: mmaly@mcmaster.ca.
authors.forename: Monica R
authors.initials: MR
authors.lastname: Maly
authors.affiliation: Department of Kinesiology, McMaster University, Ivor Wynne Centre, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada. Electronic address: pjkeir@mcmaster.ca.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Keir
authors.affiliation: Department of Medicine, McMaster University, 501-25 Charlton Ave. East, Hamilton, ON L8N 1Y9, Canada. Electronic address: sandani.h@hotmail.com.
authors.forename: Sandani M
authors.initials: SM
authors.lastname: Hapuhennedige
authors.affiliation: Faculty of Science, McMaster University, Burke Science Building (BSB), Room 102, 1280 Main Street West, Hamilton, ON L8S 4K1, Canada. Electronic address: amiekron@gmail.com.
authors.forename: Amie T
authors.initials: AT
authors.lastname: Kron
authors.affiliation: Department of Medicine, McMaster University, 501-25 Charlton Ave. East, Hamilton, ON L8N 1Y9, Canada. Electronic address: jd.adachi@sympatico.ca.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Adachi
authors.affiliation: Department of Medicine, McMaster University, 501-25 Charlton Ave. East, Hamilton, ON L8N 1Y9, Canada. Electronic address: beattik@mcmaster.ca.
authors.forename: Karen A
authors.initials: KA
authors.lastname: Beattie
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000502:physiology; D004576:Electromyography; D005260:Female; D000070633:Hamstring Muscles / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology*; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007717:Knee / Q000503:physiopathology; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000503:physiopathology*; D052097:Quadriceps Muscle / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000502:physiology*; D013848:Thigh
keywords: Adipose tissue; Electromyography; Magnetic resonance imaging; Muscle weakness/physiopathology; Osteoarthritis, knee; Quadriceps muscle