Knee OA: Women Have More Sensitivity, Overall Pain Than Men

New research from the University of Florida and the University of Alabama shows that among patients with osteoarthritis (OA) of the knee, women experienced greater sensitivity to things such as lower tolerance to heat, cold, and pressure…they also had greater widespread pain than men.

The study was led by Emily Bartley, Ph.D. of the University of Florida. She told OTW, “I was actually fortunate enough to work with Roger Fillingim during my postdoctoral training at the University of Florida. He was conducting an ongoing study with colleagues at the University of Alabama at Birmingham called UPLOAD (Understanding Pain and Limitations in OsteoArthritic Disease), with the main focus of the study being to explore ethnic differences in pain and disability in adults with knee osteoarthritis. While this was very exciting work, I had a longstanding interest in how sex differences mold the experience of pain and used this project as an opportunity to examine this particular issue. Sex differences have always been intriguing to me, not only in terms of pain, but also in the relative degree of divergence that exists between men and women in overall disease susceptibility. Pain is one of the #1 health problems in the nation, and when you look at epidemiological studies women have a significantly higher prevalence of pain when compared to men. However, when I began exploring the literature, I was surprised to find little existing research examining sex differences in knee osteoarthritis, which is stunning because knee OA is a very common condition in older adults. Therefore, I felt that this was an area worthy of addressing and seemed like a natural extension to my already established interests.”

“Interestingly, there were no sex differences in clinical pain, regardless of women being more pain-sensitive in general to the laboratory pain assessments. In fact, the only notable difference between men and women was that women reported greater widespread pain. While it is unclear why there was not a stronger concordance between self-reported pain and experimental pain sensitivity, it could be that the magnitude of sex differences in real-time assessment of pain are simply stronger than retrospective pain report in knee osteoarthritis.”

As for any hypotheses regarding these sex differences, Dr. Bartley commented to OTW, “While it would be wonderful to have a clear-cut answer to this question, it not entirely clear why these sex differences were found as this is an area that is highly complicated. Perhaps women with knee osteoarthritis may have a higher degree of central sensitivity to their pain, relative to men. This mirrors a previous study by Glass and colleagues, 2014, which found that women had greater knee pain and widespread pain than men regardless of radiological findings. Therefore, perhaps women’s knee pain has a stronger central contribution to it than men. In other words, the greater pain sensitivity observed in our female participants may be due to an amplification of pain signals in the central nervous system. However, remember that a number of factors affect sex differences in pain and that pain is, in fact, a biopsychosocial problem. Therefore, it is difficult to determine the extent to which other factors such as genetics, hormones, gender roles, etc. may have influenced these responses.”