Background/Purpose:

Knee osteoarthritis (KOA) is traditionally considered a local joint pathology. The effect of obesity on the pathogenesis of KOA is predominantly attributed to increase mechanical joint loading (local effect). Weight reduction, a well-established recommendation for overweight or obese patients with KOA, is hypothesized to improve OA symptoms via reduction in mechanical joint loading. We sought to confirm or refute the latter hypothesis.

Methods:

This is a secondary data analysis of a previously completed 18-month randomized controlled trial in KOA that compared combination diet-induced weight loss plus exercise vs. diet only vs. exercise only. In this analysis, the primary outcomes were self-report measures on pain severity (WOMAC pain) and function (WOMAC function) at the end of the study (month-18). The primary independent variables were changes in weight (kg) and knee joint compressive force (N) from baseline to month-6. Regression models were adjusted for gender, race, treatment group assignment, and baseline measures on BMI, number of comorbid illnesses, and SF36 mental component summary score (SF36 MCS).

Results:

From the 454 subjects enrolled in the original study, 329 (72.4%) subjects had available baseline and follow-up WOMAC data. This cohort had the following baseline characteristics (mean ± SD): age= 66 years ± 6.3; BMI =33.5 ± 3.6; weight (kg) = 92.7 ± 14.5; 70% females; 85% Whites; SF36 MCS= 57.1 ± 7.3; WOMAC pain (range 0-20) = 6.3 ± 3.0; and WOMAC function (range 0-68) = 23.3 ± 10.8. The mean changes (SD) in weight and knee joint compressive force from baseline to month 6 were -6.3 (6.7) kg and -60.2 (651) N, respectively.

After controlling for potential covariates, the change in weight (ß coefficient= 0.06, p=0.03) from baseline to month-6 was a significant predictor of WOMAC pain at month-18. The change in knee joint compressive force was not (p=0.68). Additionally, the change in weight (ß= 0.29, p=0.001) was a significant predictor of WOMAC function at month-18. Again, the change in knee joint compressive force was not (p>0.10).

Interestingly, gender, race, number of comorbid illnesses, and SF36 MCS were not significant in both multivariable models for WOMAC pain and function.

Conclusion:

Weight loss was temporally associated with improvement in OA symptoms through mechanisms other than reduction in mechanical joint loading. Extra-articular mechanisms (e.g., peripheral inflammation from adipokines and central sensitization) of weight loss in KOA should be explored.

« Back to 2018 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/does-reduction-in-mechanical-knee-joint-loading-explain-the-beneficial-effects-of-weight-loss-in-overweight-or-obese-patients-with-knee-osteoarthritis/