Brain Biomarker of Endogenous Analgesia in Patients With Chronic Knee Pain
Condition: Chronic Pain; Chronic Knee Pain; Knee Osteoarthritis; Analgesia
MeSH terms: Chronic Pain
Study type: Observational

Summary: 
      This case-control study in patients with knee osteoarthritis and pain-free control
      individuals aims to develop a brain biomarker of endogenous analgesia that may be used in
      subsequent clinical trials. Deficits in central nervous system (CNS) pain inhibition may
      contribute to chronic pain intensity, but quantitative sensory testing (QST) methods are
      limited. Incorporating brain imaging to assessments of CNS pain inhibition, by examining
      activity in relevant brain networks, would allow for an objective, physiologic measure of CNS
      pain inhibition. Preliminary data in pain-free volunteers implicate cortical activity
      measured with functional near-infrared spectroscopy (fNIRS) during CNS pain inhibition.
      Broadly, the investigators hypothesize that variability in CNS pain inhibition contributes to
      variability in clinical pain intensity.
    

Detailed description: 
      The objective of this study is to identify the neural correlates of central nervous system
      (CNS) pain inhibition in patients with knee osteoarthritis (OA) and determine how the
      correlates relate to clinical chronic (i.e., greater than 6 months) knee pain. To attain this
      objective, the investigators will test the following working hypotheses: (H1) in knee OA
      patients with moderate osteoarthritis but severe knee pain, cortical correlates of CNS pain
      inhibition are diminished compared to patients with less knee pain and (H2) provocation of
      clinical knee pain with ambulation produces greater pain-related cortical activation in
      patients with greater clinical knee pain at baseline. The study will also compare patients
      with knee OA to a control group to test the hypothesis (H3) that CNS pain inhibition
      behavioral and functional near-infrared spectroscopy (fNIRS) brain imaging measures are
      diminished in knee OA. Finally, in exploratory analysis, the investigators hypothesize that
      cortical functional connectivity is altered in patients with greater knee pain.

      The study approach is to measure brain activity in patients with knee osteoarthritis, divided
      into high pain intensity and low pain intensity groups, and in pain-free controls with fNIRS
      scanning during rest, quantitative sensory testing (QST) measures of CNS pain inhibition
      (conditioned pain modulation and offset analgesia), and walking and stair climbing tasks. The
      rationale is that successful completion of this study will determine whether fNIRS measures
      relate to QST measures of CNS pain inhibition and clinical pain intensity both at rest and
      during activity. This fundamental knowledge, in combination with prior studies of conditioned
      pain modulation (CPM), will be important to understanding how CNS pain inhibition may
      contribute to a range of chronic pain syndromes.
    

Observational model: Case-Control
Time perspective: Cross-Sectional
Sampling method: Non-Probability Sample
Study population: 
        Participants will be recruited from the Pitt+Me registry which comprises of any members of
        the local population who are registered in the program.