title: Pain and effusion and quadriceps activation and strength.
abstract: BACKGROUND
  Quadriceps dysfunction is a common consequence of knee joint injury and disease, yet its causes remain elusive.
  
  
  OBJECTIVE
  To determine the effects of pain on quadriceps strength and activation and to learn if simultaneous pain and knee joint effusion affect the magnitude of quadriceps dysfunction.
  
  
  METHODS
  Crossover study.
  
  
  METHODS
  University research laboratory.
  
  
  METHODS
  Fourteen (8 men, 6 women; age = 23.6 ± 4.8 years, height = 170.3 ± 9.16 cm, mass = 72.9 ± 11.84 kg) healthy volunteers.
  
  
  METHODS
  All participants were tested under 4 randomized conditions: normal knee, effused knee, painful knee, and effused and painful knee.
  
  
  METHODS
  Quadriceps strength (Nm/kg) and activation (central activation ratio) were assessed after each condition was induced.
  
  
  RESULTS
  Quadriceps strength and activation were highest under the normal knee condition and differed from the 3 experimental knee conditions (P < .05). No differences were noted among the 3 experimental knee conditions for either variable (P > .05).
  
  
  CONCLUSIONS
  Both pain and effusion led to quadriceps dysfunction, but the interaction of the 2 stimuli did not increase the magnitude of the strength or activation deficits. Therefore, pain and effusion can be considered equally potent in eliciting quadriceps inhibition. Given that pain and effusion accompany numerous knee conditions, the prevalence of quadriceps dysfunction is likely high.
authors.affiliation: School of Kinesiology, University of Michigan, Ann Arbor 48109-2214, USA. riannp@umich.edu
authors.forename: Riann M
authors.initials: RM
authors.lastname: Palmieri-Smith
authors.forename: Mark
authors.initials: M
authors.lastname: Villwock
authors.forename: Brian
authors.initials: B
authors.lastname: Downie
authors.forename: Garin
authors.initials: G
authors.lastname: Hecht
authors.forename: Ron
authors.initials: R
authors.lastname: Zernicke
mesh_terms: D000704:Analysis of Variance; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D006833:Hydrarthrosis / Q000503:physiopathology*; D007719:Knee Joint / Q000503:physiopathology*; D008297:Male; D053580:Muscle Strength / Q000502:physiology; D010146:Pain / Q000503:physiopathology*; D010147:Pain Measurement; D052097:Quadriceps Muscle / Q000503:physiopathology*; D019415:Torque; D055815:Young Adult