Brain activity for chronic knee osteoarthritis: Dissociating evoked pain from spontaneous pain

Elle L. Parks, Paul Y. Geha, Marwan N. Baliki, Jeffrey Katz, Thomas J. Schnitzer, A. Vania Apkarian*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

105 Scopus citations


Chronic pain is a hallmark of osteoarthritis (OA), yet little is known about its properties and representation in the brain. Here we use fMRI combined with psychophysics to study knee pain in fourteen OA patients and nine healthy controls. Mechanical painful pressure stimuli were applied to the knee in both groups and ratings of evoked pain and related brain activity examined. We observe that psychophysical properties and brain activation patterns of evoked pain are essentially the same between OA patients and healthy subjects, and between worse and better OA knees. In OA patients, stimulus-related brain activity could be distinguished from brain activity associated with spontaneous pain. The former activated brain regions commonly observed for acute painful stimuli in healthy subjects, while the spontaneous pain of OA engaged prefrontal-limbic regions closely corresponding to areas observed for spontaneous pain in other chronic pain conditions, such as chronic back pain and post-herpetic neuralgia. Arthritis-related clinical characteristics of knee OA also mapped to prefrontal-limbic regions. In a subgroup of patients (n = 6) we examined brain activity changes for a 2-week, repeat measure, cyclooxygenase-2 inhibitor (valdecoxib) therapy. Treatment decreased spontaneous pain for the worse knee and clinical characteristics of OA, and increased blood and csf levels of the drug which correlated positively with prefrontal-limbic brain activity. These findings indicate dissociation between mechanically induced and spontaneous OA knee pain, the latter engaging brain regions involved in emotional assessment of the self, and challenge the standard clinical view regarding the nature of OA pain.

Original languageEnglish (US)
Pages (from-to)843.e1-843.e14
JournalEuropean Journal of Pain
Issue number8
StatePublished - Sep 2011


  • COX2 inhibitor
  • Csf
  • Knee osteoarthritis
  • Limbic
  • Prefrontal cortex
  • Psychophysics
  • fMRI

ASJC Scopus subject areas

  • Anesthesiology and Pain Medicine


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