Running decreases knee intra-articular cytokine and cartilage oligomeric matrix concentrations: a pilot study.

INTRODUCTION: Regular exercise protects against degenerative joint disorders, yet the mechanisms that underlie these benefits are poorly understood. Chronic, low-grade inflammation is widely implicated in the onset and progression of degenerative joint disease.
PURPOSE: To examine the effect of running on knee intra-articular and circulating markers of inflammation and cartilage turnover in healthy men and women.
METHODS: Six recreational runners completed a running (30 min) and control (unloaded for 30 min) session in a counterbalanced order. Synovial fluid (SF) and serum samples were taken before and after each session. Cytokine concentration was measured in SF and serum using a multiplexed cytokine magnetic bead array. Ground reaction forces were measured during the run.
RESULTS: There were no changes in serum or SF cytokine concentration in the control condition. The cytokine GM-CSF decreased from 10.7 ± 9.8 to 6.2 ± 5.9 pg/ml pre- to post-run (p = 0.03). IL-15 showed a trend for decreasing concentration pre- (6.7 ± 7.5 pg/ml) to post-run (4.3 ± 2.7 pg/ml) (p = 0.06). Changes in IL-15 concentration negatively correlated with the mean number of foot strikes during the run (r 2 = 0.67; p = 0.047). The control condition induced a decrease in serum COMP and an increase in SF COMP, while conversely the run induced an increase in serum COMP and a decrease in SF COMP. Changes in serum and SF COMP pre- to post-intervention were inversely correlated (r 2 = 0.47; p = 0.01).
CONCLUSIONS: Running appears to decrease knee intra-articular pro-inflammatory cytokine concentration and facilitates the movement of COMP from the joint space to the serum.