Brain Biomarker of Endogenous Analgesia in Patients With Chronic Knee Pain

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.

Study Overview

• Status: Completed
• Conditions: Chronic Pain; Analgesia; Knee Osteoarthritis; Chronic Knee Pain

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.

• Study Type: Observational
• Enrollment (Actual): 110

Contacts and Locations

Study Locations

• United States
  • Pennsylvania
    • Pittsburgh, Pennsylvania, United States, 15206
      • UPMC Pain Medicine at Centre Commons

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 45 years to 80 years (Adult, Older Adult)
• Accepts Healthy Volunteers: Yes

• 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.

Description

Inclusion Criteria:

1. For the knee arthritis groups: Chronic knee pain with evidence of knee osteoarthritis - radiographically grades 2-4
2. Age: 45-80 years old
3. Gender: Males and females will be recruited.
4. Language: only English-speaking subjects will be included.

Exclusion Criteria:

1. Inflammatory arthritis (e.g. rheumatoid arthritis)
2. Inability to walk and climb stairs unassisted
3. History of knee replacement or open knee surgery
4. History of arthroscopic knee surgery within the last 3 months (>3 months does not exclude participant)
5. History of knee radiofrequency nerve ablation or ligation
6. Current opioid use
7. Current use of antidepressants that are not in the serotonin-selective reuptake inhibitor (SSRI) class. Patients who are currently using an SSRI are allowed to take part in the study
8. Cognitive impairment affecting the ability to provide informed consent, understand directions, and participate in study procedures
9. Uncontrolled or unstable medical disorder preventing participation in study procedures
10. History of brain surgery
11. Tattoos on forearm or knee
12. Pregnancy
13. Patients with chronic pain conditions that are more severe than their knee arthritis pain (e.g., CRPS, fibromyalgia)
14. Patients whose most painful knee is excluded for another reason (e.g., recent surgery on most painful knee)
15. For the pain-free control group: a history of chronic pain
16. History of intra-articular steroid injections, platelet enriched or hyaluronic acid injections in the last 1 month

Study Plan

How is the study designed?

Design Details

• Observational Models: Case-Control
• Time Perspectives: Cross-Sectional

Number of groups / cohorts

3

Cohorts and Interventions

Group / Cohort
High Knee Pain with Osteoarthritis; Adults 45-80 years old who have moderately severe knee osteoarthritis and rate their daily knee pain at >=6 on a 0-10 numeric rating scale
Low Knee Pain with Osteoarthritis; Adults 45-80 who have moderately severe knee osteoarthritis and rate their daily knee pain at <=5 on a 0-10 numeric rating scale
Healthy Controls; Age matched, BMI matched adults who do not have knee osteoarthritis or chronic pain

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Differences in offset analgesia	Pain intensity difference during offset and control heat stimuli	15 minutes
Differences in brain region activation- QST	Difference in brain region activation (as measured by oxygenated hemoglobin, HbO) between CNS inhibition and control stimuli during QST procedures.	2-3 hours
Differences in brain region activation- walking test	Change in brain region activation (HbO) between rest and ambulation during the 6 minute walking test test	15 minutes
Differences in brain region activation- stair climbing	Change in brain region activation (HbO) between rest and ambulation during the stair climbing test	15 minutes

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Differences in resting fNIRS signaling	Differences in fNIRS resting state connectivity as measured by brain region activation	5-10 minutes
QST battery responses	Differences in responses to QST to characterize threshold and tolerance to cutaneous thermal and mechanical stimuli	2-3 hours
Pain intensity scores after stair climbing task	Verbal score from 0-100 on numeric rating scale (NRS) of pain following stair climbing task. Higher NRS scores indicate higher pain intensity.	10 minutes
Pain intensity scores after walking test	Verbal score from 0-100 on NRS of pain following 6 minute walking task. Higher NRS scores indicate higher pain intensity.	6 minutes
Duration of stair climbing task	Differences in time taken to complete stair climbing task	10 minutes
Distance walked during 6 minute walking task	Differences in distance walked during 6 minute walking task	6 minutes
Questionnaire score- PROMIS 29	Standardized survey score of PROMIS-29 assessing physical and mental health. Physical Function Score ranges from 4-20. Anxiety Score ranges from 4-20. Depression Score ranges from 4-20. Fatigue Score ranges from 4-20. Sleep Disturbance Score ranges from 4-20. Social Roles Score ranges from 4-20. Pain Interference Score ranges from 4-20. Pain Intensity Score ranges from 0-10. Higher scores indicate worse mental and physical health.	1 hour
Questionnaire score- Knee Injury and Osteoarthritis Outcome Score (KOOS)	Standardized survey called Knee Injury and Osteoarthritis Outcome Score assessing knee pain. Scores range from 0 to 100 with a score of 0 indicating the worst possible knee symptoms and 100 indicating no knee symptoms.	1 hour
Questionnaire score- State Trait Anxiety Inventory (STAI) Y1-2	Standardized survey score of state trait anxiety inventory Y1 and Y2 assessing anxiety before QST procedures. State Anxiety Score ranges from 20-80. Trait Anxiety Score ranges from 20-80. Higher scores indicate worse anxiety state and trait symptoms.	1 hour
Questionnaire score- Pain Catastrophizing Scale (PCS)	Standardized survey score assessing pain perception before QST procedures. Rumination subscale score ranges from 0-16. Magnification subscale score ranges 0-12. Helplessness subscale score ranges from 0-24. Total score can be calculated by summing subscales. Total score ranges from 0-52, with higher scores indicating more pain catastrophizing.	1 hour
Questionnaire score- STAI Y1 post testing	Standardized survey score of state trait anxiety inventory Y1 assessing anxiety immediately after QST procedures. Higher scores indicate worse anxiety state.	1 hour
Questionnaire score- Situational Pain Catastrophizing Scale post testing	Standardized survey score assessing pain perception immediately after QST procedures are completed. Scores range from 0-24, with higher scores representing more pain catastrophizing.	1 hour
Questionnaire score- Situational Pain Catastrophizing Scale post mobility tasks	Standardized survey score assessing pain perception immediately after walking and stair climbing tasks are completed. Scores range from 0-24, with higher scores representing more pain catastrophizing.	1 hour
Questionnaire score- Beck Depression Inventory-II (BDI-II)	Standardized survey assessing depression. Scores range from 0-63. Total score of 0-13 is considered minimal range of depression, 14-19 is mild, 20-28 is moderate, and 29-63 is severe depression.	1 hour
Questionnaire score- Generalized Anxiety Disorder 2-item (GAD-2)	Standardized survey score of GAD-2 assessing anxiety. Scores range from 0-6. Higher scores indicate higher likelihood of having GAD.	1 hour
Questionnaire score- Barratt Impulsiveness Scale-11	Standardized survey score of Barratt Impulsiveness Scale-11 assessing the personality/behavioral construct of impulsiveness. Attention Impulsiveness Score ranges from 8-32. Motor Impulsiveness Score ranges from 11-44. Non-planning Impulsiveness Score ranges from 11-44. Subscale scores can be summed for a total score. Higher scores indicate greater levels of impulsivity.	1 hour
Questionnaire score- Barratt Simplified Measure of Social Status	Standardized survey score of Barratt Simplified Measure of Social Status that measures social status based on marital status, employment status, educational attainment, and occupational prestige. Total Education Score ranges from 3-21. Total Occupation Score ranges from 5-45. Total score of education and occupation can be calculated by summing the subscales with a range 8-66. Higher scores indicate a higher social status.	1 hour
Questionnaire score- Patient Health Questionnaire 2 (PHQ-2)	The PHQ-2 inquires about the frequency of depressed mood and anhedonia over the past two weeks. The PHQ-2 includes the first two items of the PHQ-9. A PHQ-2 score ranges from 0-6. The authors identified a score of 3 as the optimal cutpoint when using the PHQ-2 to screen for depression. If the score is 3 or greater, major depressive disorder is likely.	1 hour
Questionnaire score- Fibromyalgia Severity Scale	This questionnaire tests if patients meet the 2016 criteria for fibromyalgia. The symptom severity score ranges from 0-12, with higher scores indicating a higher likelihood of fibromyalgia. Three symptom question items range from 0-3, and these are summed up for the final score (totaling 0-9). Three additional symptom questions have yes or no options. If the patient answers yes, 1 point is added to the final scale.	1 hour

Collaborators and Investigators

• Sponsor: University of Pittsburgh
• Investigators: Principal Investigator: Benedict Alter, MD, PhD, University of Pittsburgh

Study record dates

Study Major Dates

• Study Start (Actual): November 18, 2021
• Primary Completion (Actual): October 20, 2023
• Study Completion (Actual): October 20, 2023

Study Registration Dates

• First Submitted: August 6, 2021
• First Submitted That Met QC Criteria: August 6, 2021
• First Posted (Actual): August 12, 2021

Study Record Updates

• Last Update Posted (Actual): March 25, 2025
• Last Update Submitted That Met QC Criteria: January 9, 2025
• Last Verified: January 1, 2025

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Pain; Neurologic Manifestations; Chronic Pain
• Other Study ID Numbers: STUDY20060254

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No