title: Changes in lower extremity muscle mass and muscle strength after weight loss in obese patients with knee osteoarthritis: a prospective cohort study.
abstract: OBJECTIVE
  To investigate the effects of low-energy diet-induced weight loss on lower-extremity muscle mass and knee muscle strength in obese patients with knee osteoarthritis (OA), and the associations of these effects.
  
  
  METHODS
  We studied 159 obese patients with knee OA and available data from body composition analysis that had been performed using dual x-ray absorptiometry scanning and isometric muscle strength testing of the knee in extension and in flexion. The data had been obtained as part of a randomized controlled trial, with measurements performed before and after a supervised low-energy diet-induced weight loss intervention lasting 16 weeks.
  
  
  RESULTS
  The patients lost an average of 12.9 kg (95% confidence interval [95% CI] 10.2, 15.7) (13% of baseline weight). The weight loss consisted of 10.9 kg fat mass (95% CI 8.9, 12.9), of which 3.8 kg (95% CI 2.7, 4.9) was leg fat mass. Total lean body mass was reduced by 1.9 kg (95% CI 0.05, 3.8), of which 0.785 kg (95% CI 0.09, 1.476) was leg lean mass. Absolute muscle strength decreased by ∼3-4% after the weight loss, whereas body mass-normalized muscle strength increased by 11-12%. At baseline, leg lean mass was significantly related to muscle strength, but changes in these measurements at followup were not related.
  
  
  CONCLUSIONS
  Weight loss induced by a low-energy diet led to independent losses of leg muscle tissue and strength. The weight loss was accompanied by increased normalized muscle strength along with improved self-reported disability and pain--all of which are beneficial to patients with knee OA. The present results suggest that significant weight loss in patients with knee OA should be followed by an exercise regimen to restore or increase muscle mass.
authors.affiliation: Clinical Motor Function Laboratory, The Parker Institute, Copenhagen University Hospital, Frederiksberg, Denmark. mh@frh.regionh.dk
authors.forename: Marius
authors.initials: M
authors.lastname: Henriksen
authors.forename: Robin
authors.initials: R
authors.lastname: Christensen
authors.forename: Bente
authors.initials: B
authors.lastname: Danneskiold-Samsøe
authors.forename: Henning
authors.initials: H
authors.lastname: Bliddal
mesh_terms: D000368:Aged; D001823:Body Composition; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D018482:Muscle, Skeletal / Q000000981:diagnostic imaging / Q000503:physiopathology*; D009765:Obesity / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology*; D020370:Osteoarthritis, Knee / Q000150:complications / Q000503:physiopathology*; D011446:Prospective Studies; D011859:Radiography; D015431:Weight Loss / Q000502:physiology*