Physical activity increases synovial fluid in ankle tendon sheaths: an adjustment of MR Criteria is needed

Abstract

Objectives: To compare the amount of uid in synovial sheaths of the ankle before and after running. Our hypothesis was that this amount would increase, and that the threshold for what is normally acceptable should be adjusted after physical activity.Methods: Twenty-one healthy volunteers (n=42 ankles) ran for 40 minutes on a treadmill. They underwent 3T MRI before and immediately after running using a dedicated ankle coil. The images were stored and subsequently measured in a standardized way and independently read by two readers for uid in the tendon sheaths in the retro and inframalleolar area. Statistics were performed for each tendon (Wilcoxon signed rank test), and also for the pooled data. Intraclass correlation coe cients were calculated.Results: For reader 1, for all tendons the values after running increased without reaching statistical signi cance. For reader 2 this was not the case for all tendons but for most. When all the data were pooled (n=800 measurements), the statistical difference before and after running was signi cant (p< 0.001).Conclusion: Data pre and post running show a trend of increasing synovial uid, however not signi cant for each individual tendon. The pooled data for all tendons, (n=800) show a statistically signi cant increase after running (p< 0.001). The clinical implication is that the threshold for normally acceptable uid should be adjusted if the patient undergoes an MR study after recent physical activity. Key PointsSynovial effusions are normally present in some of the ankle tendons Before running uid is particularily common in the medial tendon group Data pre and post running show a trend of increasing synovial uid, statistically signi cant after pooling the obtained data (p< 0.001).