Obesity, OA share 'bidirectional' relationship as drivers of pain, inflammation
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Pain in obese individuals with osteoarthritis is caused by biomechanical and inflammatory processes and may involve depression, according to a speaker at the 2021 OARSI World Congress.
Lisa Carlesso, PT, PhD, assistant professor in the School of Rehabilitation Science at McMaster University, said that obesity and OA have a “bidirectional” relationship. “A key feature of both obesity and OA is pain,” she added.
Digging deeper into these relationships, Carlesso noted that the prevalence of OA effectively doubles in obese individuals compared to non-obese individuals, while obese OA patients have double the risk of chronic pain.
However, Carlesso acknowledged that BMI is flawed as a tool for understanding these relationships. “We know that this is an imperfect measure, as this is a combination of bone, muscle and fat,” she said. “We need to be looking at adiposity and location.”
That said, Carlesso was clear that weight loss generally improves joint compressive forces. “More is better,” she said. “However, few studies have looked at load changes and how they impact pain.”
Studies to “tease out local inflammatory effects as a function of adipose tissue” would likely move the field closer to a better parameter for describing associations between weight and OA, according to Carlesso.
Adding pain to that equation, Carlesso stressed that it is important for the research and clinical communities to understand which patients are experiencing constant pain and which are experiencing intermittent pain, and why, as a function of obesity and OA. “Inflammation may drive constant pain,” she said.
Zeroing in on adipose tissue as a source of systemic inflammation, the homeostasis between adipocytes and immune cells is critical to normal cytokine production. However, in obese or dysfunctional adipose tissue, interleukin (IL)-4 and IL-10 may be affected, along with immune cells and M1 macrophages.
Adiponectin, leptin and resistin may also be implicated. “The challenge is trying to decipher their relative contribution and associations with pain,” Carlesso said.
If there is an additional component to the equation, it is depression, according to Carlesso. She described psychosocial issues as causing “interplay” between obesity, pain and OA. However, these associations have only been described in small studies. “More work needs to be done in this area to explore these associations,” she said.
Looking ahead, Carlesso called on the research community to conduct longitudinal studies, particularly those looking at gender differences in all the complex associations involving obesity, pain, depression and OA. “There is a need for further elucidation of pathways linking adiposity and its biomarkers to incident or worsening pain,” she said.
Perspective
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Obesity, osteoarthritis and pain are relevant topics in today’s society, and Lisa Carlesso, PT, PhD, provides excellent insight into the negative synergistic effects that obesity and OA can have. Considering obesity as a cause of chronic pain is something that many orthopedic surgeons, myself included, often do not consider. We often see an arthritic knee or shoulder and think we can help improve symptoms with injections or an arthroplasty procedure, but there may be more to it than that.
The systematic inflammatory effect of obesity in the body may contribute to postoperative pain in this patient population following an arthroplasty. Furthermore, it makes sense why weight loss may help these patients, as it targets both the joint compressive forces caused by the excess weight, as well as the inflammation caused by an increase in adipose tissue. Our preoperative focus on these patients may need to shift to helping control inflammation to see how much of a benefit this provides.
There are many ways to help to control systemic inflammation including NSAIDs. Turmeric, tart cherry juice and other natural anti-inflammatories may help augment the effects of NSAIDs in these patients. This is certainly an interesting area of study and one that deserves our attention moving forward.
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Carlesso L. Why do Obese Patients with OA Have More Pain? Presented at: OARSI 2021 World Congress on Osteoarthritis; April 29-May 1 (virtual meeting).
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