Background Knee osteoarthritis is more frequently found in women than men. Osteoarthritis pathophysiology is based on inflammatory and degenerative process. The role of inflammation in osteoarthritic pain is varied time over time among patients. Pain perception is different between men and women. Pain in osteoarthritis patients is not only caused by inflammatory process, but also from neurogenic and psychogenic process.
Objectives The objectives of this study were to recognize the difference of COX-2 expression by monocytes of synovial fluid and pain perception between men and women with knee osteoarthritis.
Methods This was a cross-sectional study. Eighty patients with knee osteoarthritis based on American College of Rheumatology (ACR) criteria, from Rheumatology Clinic of Sardjito Hospital, whose age more than 50 years old and agreed to participate, were selected. Subjects underwent washing period by not consuming anti-inflammatory drugs for a week. Synovial fluids were aspirated from more painful knee. Dried smear preparations were made, and stained using immunocytochemistry method. COX-2 expressions by synovial fluid monocytes were classified into 4 grades, based on monocyte cytoplasm color. Pale monocyte cytoplasm which didn't express COX-2 were scored 0, light brown monocyte cytoplasm which expressed small amount of COX-2 were scored 1, brown monocyte cytoplasm which expressed medium amount of COX-2 were scored 2, and dark brown cytoplasm which expressed large amount of COX-2 were scored 3. The individual mean scores of COX-2 expressions were calculated from the average of 100 monocytes. Knee joint pain was assessed using Visual Analogue Scale (VAS), 0 – 100 mm score. Statistical analysis was done by Duta Wacana Christian University Statistic Center.
Results There were 27 men and 53 women. Body mass index, age, and time suffering from osteoarthritis, were not different between groups. The mean ± SD of COX-2 expression scores were 1.95±0.36 in men and 1.80±0.38 in women. COX-2 expression scores were significantly higher (p=0.038) in men (median (IQR), 2.14 (0.63)) compared to women (median (IQR), 1.81 (0.62)). VAS scores were significantly higher (p=0.035) in women (mean ± SD: 56.52±22.67 mm) than men (mean ± SD: 44.33±26.43 mm).
Conclusions In patients with knee osteoarthritis, women had more severe pain despite lower COX-2 enzyme expressed by synovial fluid monocytes than men.
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Disclosure of Interest None declared
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