Purpose: Obesity is known to be a risk factor for the incidence and progression of prevalent osteoarthritis (OA). The relationship is traditionally believed to be a mechanical effect on weight bearing joints such as the hip and knee, however studies showing a relationship between body mass index (BMI) and OA of non-weight bearing joints, such as the hand, suggest another theory. They suggest that the relationship between obesity and joint degeneration may be a systemic metabolic effect whereby visceral and sub-cutaneous truncal white adipose tissue (WAT) secrete inflammatory mediators that directly influence the pathogenesis of OA. We asked what is the relationship between adiponectin, leptin, and the A/L ratio and patient reported pain in an end stage knee OA joint population.
Method: We collected demographic data, Short Form McGill Pain scores, WOMAC pain scores, and synovial fluid (SF) samples from 60 consecutive patients with severe knee OA at the time of joint replacement surgery. Synovial fluid samples were analyzed for leptin and adiponectin using specific ELISA. Non-parametric correlations and linear regression modeling were used to identify the relationship between the adipokines and pain levels.
Results: The correlations between the individual adipokines and the pain scales were consistently less than that for the corresponding adipokine ratio. The A/L ratio correlated moderately with the MPQ-SF, (r(58) = − 0.46, p < .01) and the WOMAC pain score, (r(58) = − 0.38, p > .01). Linear regression modeling demonstrated that the A/L ratio was a significant predictor of a greater level of pain on the MPQ-SF(p=0.03, Table 3) but not the WOMAC pain scale(p=0.77, Table 4). Models were adjusted for age, gender, BMI, and medical comorbidity.
Conclusion: In conclusion, a greater A/L ratio predicted lower knee OA pain as measured by the MPQ-SF, but not on the WOMAC pain scale. This finding was above that of the individual adipokine levels alone. Some authors have suggested that leptin may have a proin-flammatory role while adiponectin an anti-inflammatory role in synovial joint diseases. Further work to elucidate these pathways may present a target for novel therapeutics in knee OA.
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