title: Experimental pain sensitivity differs as a function of clinical pain severity in symptomatic knee osteoarthritis.
abstract: OBJECTIVE
  Pain in knee osteoarthritis (OA) has historically been attributed to peripheral pathophysiology; however, the poor correspondence between objective measures of disease severity and clinical symptoms suggests that non-local factors, such as altered central processing of painful stimuli, also contribute to clinical pain in knee OA. Consistent with this notion, recent evidence demonstrates that patients with knee OA exhibit increased sensitivity to painful stimuli at body sites unaffected by clinical pain.
  
  
  METHODS
  In order to further investigate the contribution of altered pain processing to knee OA pain, the current study tested the hypothesis that symptomatic knee OA is associated with enhanced sensitivity to experimental pain stimuli at the knee and at remote body sites unaffected by clinical pain. We further anticipated that pain sensitivity would differ as a function of the OA symptom severity. Older adults with and without symptomatic knee OA completed a series of experimental pain assessments. A median split of the Western Ontario and McMaster Universities Index of Osteoarthritis (WOMAC) was used to stratify participants into low vs high OA symptom severity.
  
  
  RESULTS
  Compared to controls and the low symptom group, individuals in the high symptom group were more sensitive to suprathreshold heat stimuli, blunt pressure, punctuate mechanical, and cold stimuli. Individuals in the low symptomatic OA group subgroup exhibited experimental pain responses similar to the pain-free group on most measures. No group differences in endogenous pain inhibition emerged.
  
  
  CONCLUSIONS
  These findings suggest that altered central processing of pain is particularly characteristic of individuals with moderate to severe symptomatic knee OA.
authors: University of Florida Pain Research and Intervention Center of Excellence (PRICE), FL 32610, USA. kingpininflorida@gmail.com
authors: C D
authors: CD
authors: King
authors: K T
authors: KT
authors: Sibille
authors: B R
authors: BR
authors: Goodin
authors: Y
authors: Y
authors: Cruz-Almeida
authors: T L
authors: TL
authors: Glover
authors: E
authors: E
authors: Bartley
authors: J L
authors: JL
authors: Riley
authors: M S
authors: MS
authors: Herbert
authors: A
authors: A
authors: Sotolongo
authors: J
authors: J
authors: Schmidt
authors: B J
authors: BJ
authors: Fessler
authors: D T
authors: DT
authors: Redden
authors: R
authors: R
authors: Staud
authors: L A
authors: LA
authors: Bradley
authors: R B
authors: RB
authors: Fillingim
mesh_terms: D059787:Acute Pain / Q000503:physiopathology* / Q000523:psychology; D018771:Arthralgia / Q000209:etiology / Q000503:physiopathology* / Q000523:psychology; D015992:Body Mass Index; D004185:Disability Evaluation; D004522:Educational Status; D005260:Female; D006358:Hot Temperature / Q000009:adverse effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000150:complications / Q000503:physiopathology* / Q000523:psychology; D010147:Pain Measurement; D017288:Pain Threshold / Q000502:physiology* / Q000523:psychology; D010812:Physical Stimulation / Q000009:adverse effects; D011312:Pressure / Q000009:adverse effects; D012720:Severity of Illness Index
keywords: Experimental pain; Knee osteoarthritis; Severity; WOMAC
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