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Knee osteoarthritis severity doesn’t correlate well with pain

PainSci » bibliography » Finan et al 2012
Tags: etiology, patellar pain, chronic pain, arthritis, biomechanics, pro, aging, pain problems, knee, leg, limbs, overuse injury, injury, running, exercise, self-treatment, treatment

Two articles on PainSci cite Finan 2012: 1. The Complete Guide to Patellofemoral Pain Syndrome2. Your Back Is Not Out of Alignment

PainSci notes on Finan 2012:

Many lines of evidence suggest that pain is not tightly linked to tissue damage. If so, there should be people with knees that look bad on a scan, but feel fine, and vice versa. This study of 113 people found exactly that: as Tony Ingram summarized it, people “who had a little arthritis and high pain and people with severe arthritis but low pain.”

And why did the hurters hurt? High sensitivity to pain in general: “central sensitization” (see Woolf). Their knees weren’t the problem — their nervous systems were.

original abstract Abstracts here may not perfectly match originals, for a variety of technical and practical reasons. Some abstacts are truncated for my purposes here, if they are particularly long-winded and unhelpful. I occasionally add clarifying notes. And I make some minor corrections.

OBJECTIVE: Radiographic measures of knee osteoarthritis (K-OA) pathology have modest associations with clinical pain. We sought to evaluate possible differences in quantitative sensory testing (QST), and psychosocial distress profiles between K-OA patients with discordant versus congruent clinical pain reports relative to radiographic severity measures.

PATIENTS AND METHODS: 113 participants (67% women, Mean age = 61.05 ± 8.93) with K-OA participated in the study. Radiographic joint pathology was graded via the Kellgren-Lawrence scale. Central sensitization was indexed through quantitative sensory testing, including heat and pressure pain threshold, tonic suprathreshold pain (cold pressor test), and repeated phasic suprathreshold mechanical and thermal pain. Subgroups were constructed by dichotomizing clinical knee pain scores (median split) and knee grade scores (1-2 vs. 3-4), resulting in four groups: Low Pain/Low Knee Grade (n=24), High Pain/Low Knee Grade (n=30), Low Pain/High Knee Grade (n=27), and High Pain/High Knee Grade (n=32).

RESULTS: Multivariate analyses revealed significantly heightened pain sensitivity in the High Pain/Low Knee Grade group, while the Low Pain/High Knee Grade group was less pain sensitive. Group differences remained significant after adjusting for differences on psychosocial measures, as well as age, sex, and race.

CONCLUSION: The results suggest that central sensitization in K-OA is especially apparent among patients with high clinical pain reports in the absence of moderate to severe radiographic evidence of K-OA pathology.

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