Changes in pain sensitization and depressive symptoms may partially mediate reduction in knee pain after substantial weight loss in morbidly obese individuals with knee pain, according to study results published in Arthritis & Rheumatology.

In this study, 75 morbidly obese patients with frequent knee pain were assessed for bone marrow lesions, synovitis evaluated on magnetic resonance imaging (MRI), pressure pain threshold, the Western Ontario and McMaster Universities Osteoarthritis (WOMAC) Index score, and the presence of depressive symptoms with the Center for Epidemiologic Studies Depression Scale (CES-D) prior to bariatric surgery (n=47) or medical weight management (n=28) and 1 year after the intervention.

In this cohort, 53.3% of individuals lost ≥20% weight in the first year and 75% achieved minimal clinically important difference (MCID) in pain improvement (ie, ≥18% on the WOMAC pain). In individuals who lost <20% weight, 34.3% achieved MCID.

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Patients who lost ≥20% weight vs <20% were found to have increased odds of MCID pain improvement if they experienced changes in the following: patella pain threshold (odds ratio [OR], 1.62-fold; 95% CI, 0.89-2.75-fold change; 62% increased odds), wrist pain threshold (OR, 1.15- fold; 95% CI, 0.77-1.77-fold change; 15% increased odds), and depressive symptoms (OR, 1.22-fold; 95% CI, 0.77-1.87-fold; 22% increased odds). Improvements in pain were not found to be mediated by MRI changes in bone marrow lesions or synovitis.

Study limitations include a relatively small sample that was almost entirely composed of women.

“Our findings suggest that changes in pain sensitization and in depressive symptoms mediate in part the knee pain improvement experienced by those undergoing substantial weight loss, especially following bariatric surgery,” noted the study investigators. “This suggests that pain sensitization and depressive symptoms could be a promising target for future intervention studies in those with chronic knee pain.”

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Jafarzadeh SR, Neogi T, Li JS, et al. Mediating role of bone marrow lesion, synovitis, pain sensitization, and depressive symptoms on knee pain improvement following substantial weight loss [published online September 28, 2019]. Arthritis Rheumatol. doi:10.1002/art.41125