Background/Purpose:  Knee pain is the most common manifestation of knee osteoarthritis (OA) and typically accompanied by pain at other sites. Knee structural pathology in MRI, such as bone marrow lesions (BMLs), effusion and cartilage defects, appear to be strongly associated with knee OA-pain through abnormal excitability in peripheral and central pathways. However, whether persistent multi-site pain (MSP) is maintained by long-lasting peripheral structural pathology remains unknown. This study, therefore, aimed to determine whether long-lasting knee structural pathology–BMLs, effusion and cartilage defects is associated with persistent MSP and explore the underlying mechanisms.

Methods:  Data from the prospective Tasmanian Older Adult Cohort study was utilized. Knee pain and pain at other sites (neck, back, hands, shoulders, hips and feet) was measured by a questionnaire at baseline and 2.6 years later. T1-weighted or T2-weighted fat saturated MRI of the right knee was performed to assess the BMLs, effusion and cartilage defects at baseline and 2.6 years. Knee radiographic OA was assessed by X-ray at baseline. Long-lasting structural lesion was defined as the presence of a lesion at both baseline and follow-up. Persistent MSP was defined as the presence of knee pain plus other site pain at both baseline and follow-up. Logistic regression modelling was used with adjustment for potential confounders.

Results:  In 394 participants (mean age 63 years, mean BMI of 27.3 kg/m² and 51% women), 25% of participants with knee pain had pain present in at least one other site at baseline and 2.6 years. The presence of BMLs, effusion and cartilage defects at both baseline and follow-up were: 38%, 26% and 30% of the participants, respectively. Persistent knee pain plus other site pain was respectively associated with long-lasting BMLs (OR 1.94, 95% CI 1.13 to 3.33), effusion-synovitis (OR 2.24, 95% CI 1.24 to 4.03), and cartilage defects (OR 2.33, 95% CI 1.31 to 4.13) in multivariable analyses. However, there was no significant association of the presence of knee structural pathology only at either baseline or follow-up with persistent knee pain plus other site pain (all P>0.05).

Conclusion:  Longer duration of the presence of BMLs, effusion and cartilage defects is associated with persistent knee pain plus other site pain, suggesting that nociceptive input induced by knee structural lesions may be a key factor in the maintenance of persistent multi-site pain in which sensitization may be implicated. The importance of this to clinicians and researchers is that the timing of treatment of knee structural pathology may normalize the increased sensitivity (sensitization).

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/long-lasting-local-knee-structural-pathology-is-associated-with-persistent-multi-site-pain/