A study published recently in Arthritis & Rheumatology provides evidence suggesting strong associations between knee osteoarthritis and obesity in both men and women. Research should focus on the role of inflammation in the two conditions, experts note.
“In this large longitudinal cohort, we found body composition-based obesity and sarcopenic obesity, but not sarcopenia, to be associated with risk of knee osteoarthritis,” Devyani Misra, MD, of Beth Israel Deaconess Medical Center in Boston, and colleagues, write.
“Weight loss strategies for knee osteoarthritis should focus on obesity and sarcopenic obesity,” they add, in a media release from MedPage Today.
The study included 1,653 participants, 61% of whom were women, with a mean age of 62 and a mean body mass index of 30. Among the participants, 315 (19%) developed incident radiographic knee osteoarthritis by the 60-month mark of the study.
Misra and colleagues found greater fat mass to be numerically and statistically associated with increased knee osteoarthritis risk at 60 months in the overall population (RR 1.02 [95% CI 1.0-1.04]) and in women (RR 1.03 [95% CI 1.00-1.06]). In men, fat mass was not associated with risk of knee osteoarthritis — RR 1.00 (95% CI 0.95-1.13).
The results were similar between men and women when evaluating body composition based on fat and muscle mass in those categorized as obese, sarcopenic obese, or sarcopenic. Participants who were either obese (RR 2.05 [95% CI 1.56-2.68]) or sarcopenic obese (RR 1.91 [95% CI 1.17-3.10]) had an increased risk of knee osteoarthritis over 60 months.
The results in women and men were similar: women who were obese had a more than a two-fold increased risk of radiographic knee osteoarthritis (RR 2.29 [95% CI 1.64-3.20]). A similar finding occurred in women who were sarcopenic obese (RR 2.09 [95% CI 1.17-3.73]).
In men, there was a >70% increased risk of radiographic knee osteoarthritis among those who were obese (RR 1.73 [95% CI 1.08-2.78]) and sarcopenic obese (RR 1.74 [95% CI 0.68-4.46]), although in the latter case the results did not reach statistical significance.
No significant association between sarcopenia without obesity and risk of radiographic knee osteoarthritis was found in either the overall analysis (RR 0.87 [95% CI 0.06-1.25]) or the sex-stratified analyses (for women, RR 0.96 [95% CI 0.62-1.49]; for men, RR 0.66 [95% CI 0.34-1.30]), the release explains.
Misra and colleagues state that the findings should inform how rheumatologists and other care providers approach weight-loss strategies for relevant patients.
“Our findings have implications for management of knee osteoarthritis, such that weight loss interventions should target both high fat mass and low muscle mass,” the researchers write.
Relatively little is known about the relationship between obesity, inflammation, and osteoarthritis. It is well known that fat cells release adipokines including leptin as an immune protein, and that adipokines can cause lower-level inflammation over time.
But the specific interplay is still not widely understood, particularly in comparison with the more obvious problems that occur when joints are supporting abnormally high amounts of weight.
The connection between osteoarthritis, obesity, and inflammation could be a key research area moving forward, experts say, the release continues.
“It’s not just wear and tear or weight bearing,” states Lydia Alexander, MD, an obesity specialist in San Francisco who was not affiliated with the study. “The issue should also be inflammation. We know that obesity has a lot of chemical components within it, and inflammation could be at play.”
The issue has high importance given the large numbers of Americans receiving knee replacement surgeries — many of them as a result of obesity, osteoarthritis, or both. According to a 2018 study in the Journal of Bone & Joint Surgery, the number of total knee arthroplasties is expected to rise 85% to 1.26 million procedures by 2030.
Better understanding and management of obesity could help avoid surgeries, not to mention the other problems obesity can create, Alexander adds. “Osteoarthritis and diabetes are the two biggest problems we have. And obesity, whether upstream or downstream, just makes them worse.”
[Source: MedPage Today]