title: Decrease of muscle strength is associated with increase of activity limitations in early knee osteoarthritis: 3-year results from the cohort hip and cohort knee study.
abstract: OBJECTIVE
  To determine whether a decrease in muscle strength over 3 years is associated with an increase in activity limitations in persons with early symptomatic knee osteoarthritis (OA), and to examine whether the longitudinal association between muscle strength and activity limitations is moderated by knee joint proprioception and laxity.
  
  
  METHODS
  A longitudinal cohort study with 3-year follow-up. Measurements were performed at the second (t0) and fifth (t1) year of the Cohort Hip and Cohort Knee (CHECK) study. Statistical analyses included paired t tests, chi-square tests, and regression analyses. In regression analyses, the association between muscle strength and activity limitations was adjusted for confounders.
  
  
  METHODS
  A rehabilitation and rheumatology center.
  
  
  METHODS
  Subjects (N=146) with early symptomatic knee OA from the CHECK study.
  
  
  METHODS
  Not applicable.
  
  
  METHODS
  Muscle strength, proprioception, and laxity were assessed using specifically designed measurement devices. Self-reported and performance-based activity limitations were measured with the Western Ontario and McMaster Universities Osteoarthritis Index, the Get Up and Go test, the walk test, and the stair-climb test.
  
  
  RESULTS
  A total of 116 women (79.5%) and 30 men (20.5%), with a mean age ± SD of 58.4±4.9 years and a mean body mass index ± SD of 25.5±3.6, were included in the study. Overall, small 3-year changes in muscle strength and activity limitations were observed. At the group level, the average muscle strength increased by 10% (1.0±0.3 to 1.1±0.3Nm/kg) over the 3 years. The 3-year decrease in muscle strength was independently associated with an increase in performance-based activity limitations on all 3 measures (B=-1.12, B=-5.83, and B=-1.25, respectively). Proprioception and laxity did not moderate this association.
  
  
  CONCLUSIONS
  In patients with early knee OA, decreased muscle strength is associated with an increase in activity limitations. Our results are a step toward understanding the role of muscle weakness in the development of activity limitations in knee OA. Further well-designed experimental studies are indicated to establish the causal role of muscle weakness in activity limitations.
authors: Amsterdam Rehabilitation Research Center, Reade, Amsterdam, The Netherlands. Electronic address: m.vd.esch@reade.nl.
authors: Martin
authors: M
authors: van der Esch
authors: Amsterdam Rehabilitation Research Center, Reade, Amsterdam, The Netherlands.
authors: Jasmijn F
authors: JF
authors: Holla
authors: Amsterdam Rehabilitation Research Center, Reade, Amsterdam, The Netherlands; Department of Rehabilitation Medicine, VU University Medical Center, Amsterdam, The Netherlands; EMGO Institute for Health and Care Research, VU University Medical Center, Amsterdam, The Netherlands.
authors: Marike
authors: M
authors: van der Leeden
authors: EMGO Institute for Health and Care Research, VU University Medical Center, Amsterdam, The Netherlands; Department of Epidemiology and Biostatistics, VU University Medical Center, Amsterdam, The Netherlands.
authors: Dirk L
authors: DL
authors: Knol
authors: Department of Rheumatology, VU University Medical Center, Amsterdam, The Netherlands; Jan van Breemen Research Institute, Reade, Amsterdam, The Netherlands.
authors: Willem F
authors: WF
authors: Lems
authors: Amsterdam Rehabilitation Research Center, Reade, Amsterdam, The Netherlands.
authors: Leo D
authors: LD
authors: Roorda
authors: Amsterdam Rehabilitation Research Center, Reade, Amsterdam, The Netherlands; Department of Rehabilitation Medicine, VU University Medical Center, Amsterdam, The Netherlands; EMGO Institute for Health and Care Research, VU University Medical Center, Amsterdam, The Netherlands; Department of Psychiatry, VU University Medical Center, Amsterdam, The Netherlands.
authors: Joost
authors: J
authors: Dekker
mesh_terms: D001696:Biomechanical Phenomena; D015331:Cohort Studies; D004185:Disability Evaluation; D005080:Exercise Test; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000209:etiology / Q000503:physiopathology; D007719:Knee Joint / Q000503:physiopathology; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D051346:Mobility Limitation; D009043:Motor Activity / Q000502:physiology*; D053580:Muscle Strength / Q000502:physiology*; D020370:Osteoarthritis, Knee / Q000150:complications / Q000503:physiopathology* / Q000534:rehabilitation; D011434:Proprioception / Q000502:physiology; D052097:Quadriceps Muscle / Q000503:physiopathology*; D057566:Self Report; D016138:Walking / Q000502:physiology
keywords: Activities of daily living; Longitudinal studies; Muscle strength; Osteoarthritis, knee; Proprioception; Rehabilitation