title: Effect of quadriceps strength and proprioception on risk for knee osteoarthritis.
abstract: OBJECTIVE
  Impaired quadriceps strength and joint position sense (JPS) have been linked with knee osteoarthritis (OA) cross-sectionally. Although neither has been independently associated with incident radiographic OA, their combination may mediate risk. The purpose of this study was to determine whether better sensorimotor function protects against the development of incident radiographic or symptomatic knee OA.
  
  
  METHODS
  The Multicenter Osteoarthritis study is a longitudinal study of adults aged 50–79 yr at high risk for knee OA. Participants underwent bilateral, weight-bearing, fixed-flexion radiographs, JPS acuity tests, and isokinetic quadriceps strength tests. The relationships between combinations of the tertiles of sex-specific baseline peak strength and mean JPS and development of incident radiographic (Kellgren–Lawrence (KL) grade Q2) or symptomatic knee OA (KL grade Q2 and frequent knee pain or stiffness) at a 30-month follow-up were evaluated. Secondary analyses defined JPS as the variance during the 10 JPS trials and also assessed the interaction of strength and JPS in predicting each outcome.
  
  
  RESULTS
  The study of incident radiographic knee OA included 1390 participants (age = 61.2 ± 7 .9 yr and body mass index = 29.4 ± 5.1 kg·m−²), and the study of incident symptomatic knee OA included 1829 participants (age = 62.2 ± 8.0 yr and body mass index = 30.0 ± 5.4 kg·m−²). Greater strength at baseline protected against incident symptomatic but not radiographic knee OA regardless of JPS tertile. There was no significant relationship between the strength–JPS interaction and the development of radiographic or symptomatic knee OA.
  
  
  CONCLUSIONS
  The finding that quadriceps strength protected against incident symptomatic but not radiographic knee OA regardless of JPS tertile suggests that strength may be more important than JPS in mediating risk for knee OA.
authors.affiliation: Departments of Orthopaedics and Rehabilitation, Radiology, and Epidemiology, The University of Iowa, Iowa City, IA 52242-1088, USA. segal-research@uiowa.edu
authors.forename: Neil A
authors.initials: NA
authors.lastname: Segal
authors.forename: Natalie A
authors.initials: NA
authors.lastname: Glass
authors.forename: David T
authors.initials: DT
authors.lastname: Felson
authors.forename: Michael
authors.initials: M
authors.lastname: Hurley
authors.forename: Mei
authors.initials: M
authors.lastname: Yang
authors.forename: Michael
authors.initials: M
authors.lastname: Nevitt
authors.forename: Cora E
authors.initials: CE
authors.lastname: Lewis
authors.forename: James C
authors.initials: JC
authors.lastname: Torner
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D020370:Osteoarthritis, Knee / Q000209:etiology*; D011434:Proprioception / Q000502:physiology*; D052097:Quadriceps Muscle / Q000502:physiology*; D018570:Risk Assessment; D014481:United States