Background/Purpose: Many people with knee OA have bone marrow lesions (BMLs). BMLs are related with structural pathology and pain. Some investigators have found an association between strenuous physical activity and increased BML volume, leading to a potential increase in pain. Because of the health benefits of exercise, it is important to determine if physical activity could affect pain levels in patients who have knee OA. The purpose of this study was to determine if physical activity influences the existing relationship between BMLs and pain.

Methods: To determine if exercise has an effect on the relationship between BMLs and pain, we performed an exploratory analysis on a sample of 85 knees with BMLs from the Osteoarthritis Initiative (OAI). To determine the presence of a BML, one reader (AC), used customized software to segment the BML volume (patella, tibiofemoral; intraclass correlation coefficient ≥ 0.96) on paired baseline and 24-month MRIs. All MRI scans and measurements were assessed for quality with another reader (JD). To measure physical activity, we used the Physical Activity Scale for the Elderly (PASE). The questions on walking, light sport/recreation, moderate sport/recreation, and strenuous sport/recreation of the Physical Activity Scale for the Elderly (PASE) were used to calculate exercise hours per week. To get a more accurate picture of typical physical activity in our sample, we took the average of 0, 12-, and 24-month exercise hours. To measure pain, we used the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscale (range 0-20). A change of 2 points was considered clinically meaningful. We assessed two exercise categories: any vs. none. Spearman correlations were calculated. Ordinal logistic regression was used to assess the relationship between change in WOMAC pain (improved, no change, worsened) and exercise category. We adjusted for age, sex, and BMI.

Results: The study population was mostly white (81%), female (58%), and had KL grades 2 (38%) or 3 (53%) at baseline. 63 participants (74%) exercised. Of those who exercised, 96.5% walked, 27.1% participated in light recreation, 38.8% participated in moderate recreation, and 49.4% participated in strenuous recreation for at least one time point. There was no significant difference in the change in WOMAC pain between those who did or did not exercise (p=0.59) (Table 1). In the group that exercised, there was a weak positive correlation (r= 0.27, p=0.037) between total BML at baseline and change in WOMAC pain scores. In the group that did not exercise, there was a weak negative correlation (r= -0.19, p=0.44) between total BML at baseline and change in WOMAC pain score.

Conclusion: When adjusted, BMLs are associated with pain, but only among those who exercise. As our population was relatively sedentary, this study may not be generalizable to a population that regularly participates in vigorous exercise.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/an-exploratory-analysis-of-physical-activity-levels-and-the-presence-of-bone-marrow-lesions-in-adults-with-knee-osteoarthritis-data-from-the-osteoarthritis-initiative/