Why People with Knee Osteoarthritis Experience Different Kinds of Pain

Summary: People with osteoarthritis in the knee who report more pain sensations are more likely to suffer constant and unpredictable pain. Researchers identified a potential mechanism in the nervous system that could explain why people experience varying pain patterns associated with knee osteoarthritis.

Source: Boston University

Osteoarthritis is the most common form of arthritis worldwide, affecting more than 300 million people. It causes substantial pain, functional limitations, and disability in patients.

The pain experience in patients with knee osteoarthritis changes over time. People initially experience primarily weight-bearing related pain, such as with jogging and stair-climbing. Over time, the pain becomes more persistent and can flare unpredictably.

To better understand why this change in the pain experience occurs, researchers from the Boston University schools of Medicine (BUSM) and Public Health reviewed data from the Multicenter Osteoarthritis Study about the pain experience of 2,794 older adults with or at risk of knee osteoarthritis.

They found that people with more pain sensitization were more likely to suffer from constant and unpredictable pain, rather than just intermittent pain.

This study has identified for the first time a potential underlying mechanism in the nervous system responsible for why people experience varying pain patterns with knee osteoarthritis.

“Our findings support the clinical relevance of neurobiological mechanisms that affect the pain experience in knee osteoarthritis, including not only the severity of pain, but whether the pain is intermittent or constant, and whether the pain is unpredictable,” said senior author Tuhina Neogi, MD, PhD, professor of medicine and epidemiology at BUSM.

This shows a knee
This study has identified for the first time a potential underlying mechanism in the nervous system responsible for why people experience varying pain patterns with knee osteoarthritis. Image is in the public domain.

By understanding the different mechanisms that contribute to the pain experience of knee osteoarthritis, healthcare providers can begin to personalize pain management to each patient. For example, if a patient has pain sensitization, therapies that can alter those nervous system signaling pathways may be helpful. This would improve the current ‘one-size-fits-all’ approach, in which each patient is started with the same treatment and then moved on to something else if the first approach did not work.

“By understanding these mechanisms, determining ways to identify those mechanisms in the clinic, and developing treatments to target those mechanisms, we can provide better management options to the millions of people worldwide with osteoarthritis,” said Dr. Neogi.

Funding: Dr Neogi’s work is supported by US National Institutes of Health (NIH) grants P30AR072571, K24-AR070892, R01-AR062506, and R01-AG066010. The Multicenter Osteoarthritis Study is supported by NIH grants U01-AG-18820, U01-AG-18832, U01-AG-18947, and U01-AG-19079.

About this pain research article

Source:
Boston University
Contacts:
Press Office – Boston University
Image Source:
The image is in the public domain.

Original Research: Closed access
“The Association of Pain Sensitization and Conditioned Pain Modulation to Pain Patterns in Knee Osteoarthritis” by Neogi et al. Arthritis Care & Research.


Abstract

The Association of Pain Sensitization and Conditioned Pain Modulation to Pain Patterns in Knee Osteoarthritis

Objectives
To examine the cross‐sectional association of ascending pain mechanisms (APM), implicated in pain sensitization (PS), and descending pain modulation with pain patterns and unpredictability of pain.

Methods
The Multicenter Osteoarthritis (OA) Study is a longitudinal cohort of older adults with or at risk of knee OA. Peripheral and central APM were assessed using quantitative sensory tests (QST); pressure pain thresholds (PPTs) using a handheld pressure algometer (knee/peripheral and wrist/central), temporal summation (TS) using weighted probes (wrist/central). Descending modulation was assessed by conditioned pain modulation (CPM) using PPTs and a forearm ischemia test. Pain patterns were characterized based on responses to the Intermittent and Constant OA Pain (ICOAP) questionnaire: 1) no intermittent or constant pain; 2) intermittent pain only; 3) constant pain only; and 4) combined constant and intermittent pain. A question regarding frequency assessed unpredictable pain. We assessed the association of QST measures to pain patterns using regression models with generalized estimating equations.

Results
There were 2794 participants (mean age 63.9, BMI 29.5 kg/m2, 57% female). Lower PS (by wrist PPT) OR = 0.80 (95% CI 0.68, 0.93) and adequate CPM, OR = 1.45 (1.10, 1.92) were associated with having constant +/‐ intermittent pain compared with intermittent pain only. Higher PS (by PPT and TS) was associated with higher likelihood of unpredictable pain.

Conclusions
Knee pain patterns appear to be related to peripheral +/‐ central facilitated APM, and descending modulatory mechanisms. These findings highlight the need for a broader approach to understanding pain mechanisms by symptomatic disease progression.

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