Synovitis and effusion were associated with increases in pain sensitivity at the patella and wrist, respectively, in a study of 1,111 patients with or at risk of knee osteoarthritis (OA).
Radiographs and MRIs were taken of the patients’ knees, and the patients wrists and patellae were subjected to standardized quantitative sensory testing (QST) measures. The QST measures included temporal summation, which is a measure of central pain amplification based on “an augmented response to repetitive mechanical stimulation,” and pressure pain threshold (PPT), a measure of sensitivity to pain evoked by mechanical stimulation of nociceptors. (Lower PPTs represent a greater degree of sensitization or pain sensitivity.) All tests were conducted at baseline and 2 years later.
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Synovitis was associated with a significant decrease in PPT at the patella, while effusion was associated with a decrease in PPT at the wrist. Effusion was additionally associated with risk of incident temporal summation. In contrast to synovitis and effusion, bone marrow lesions were not associated with either temporal summation or decreased pressure pain threshold.
“Our findings support the potential relevance of inflammation in the development and heightening of sensitization in knee osteoarthritis in humans. We found that synovitis was associated with lower PPT and a decrease in PPT at the patella over time, indicating increased pain sensitization or sensitivity. Effusion was associated with development of new temporal summation at the patella, and with a decrease in PPT at the wrist, a site distant to the pathology; both findings suggest the involvement of central sensitization. Thus inflammation appears to influence the development of and perhaps amplification of sensitization,” said Dr. Tuhina Neogi, of the department of medicine at Boston University and her colleagues.
Read the full study in Arthritis & Rheumatology (doi: 10.1002/art.39488).