title: Avoidance of activity and limitations in activities in patients with osteoarthritis of the hip or knee: a 5 year follow-up study on the mediating role of reduced muscle strength.
abstract: OBJECTIVE
  To evaluate the mediating role of reduced muscle strength in the relationship between avoidance of activity and limitations in activities in patients with knee or hip osteoarthritis (OA).
  
  
  METHODS
  A longitudinal cohort study with 5 years follow-up was conducted. Patients with knee or hip OA (n = 288) were recruited at rehabilitation centers and hospitals. Self-reported and performance based limitations in activities, avoidance of activity and muscle strength were assessed at baseline, 1, 2, 3 and 5 years follow-up. Generalized Estimating Equations (GEE) analyses were used to evaluate mediation.
  
  
  RESULTS
  In patients with knee OA, reduced knee extensor muscle strength mediated the relationship between avoidance of activity and limitations in activities. In patients with hip OA reduced hip abductor muscle strength mediates the relationship between avoidance of activity and limitations in activities.
  
  
  CONCLUSIONS
  The results of this longitudinal study support the theory that avoidance of activity leads to deterioration of muscle strength and consequently to more limitations in activities in patients with knee and hip OA.
authors: Physical Therapy Research, Program in Clinical Health Sciences & Department of Rehabilitation, Nursing Science and Sport, Brain Center Rudolf Magnus, University Medical Center Utrecht, Utrecht, The Netherlands; Department of Health, Innovations & Technology, Fontys University of Applied Sciences, Eindhoven, The Netherlands. Electronic address: m.f.pisters@umcutrecht.nl.
authors: M F
authors: MF
authors: Pisters
authors: Netherlands Institute for Health Services Research (NIVEL), Utrecht, The Netherlands.
authors: C
authors: C
authors: Veenhof
authors: Department of Epidemiology, Erasmus MC, University Medical Centre Rotterdam, Rotterdam, The Netherlands.
authors: G M
authors: GM
authors: van Dijk
authors: Department of Rehabilitation Medicine & Department of Psychiatry, EMGO Institute, VU University Medical Center Amsterdam, Amsterdam, The Netherlands.
authors: J
authors: J
authors: Dekker
mesh_terms: D000203:Activities of Daily Living; D000368:Aged; D000369:Aged, 80 and over; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology*; D018908:Muscle Weakness / Q000209:etiology / Q000503:physiopathology; D018482:Muscle, Skeletal / Q000503:physiopathology; D015207:Osteoarthritis, Hip / Q000150:complications / Q000503:physiopathology / Q000534:rehabilitation*; D020370:Osteoarthritis, Knee / Q000150:complications / Q000503:physiopathology / Q000534:rehabilitation*; D010146:Pain / Q000209:etiology; D057566:Self Report
keywords: Avoidance of activity; Limitations in activities; Muscle strength; Osteoarthritis; Physical activity