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

Robert D. Hyldahl, Alyssa Evans, Sunku Kwon, Sarah T. Ridge, Eric Robinson, J. Ty Hopkins, Matthew K. Seeley

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. To examine the effect of running on knee intra-articular and circulating markers of inflammation and cartilage turnover in healthy men and women. 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. 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). Running appears to decrease knee intra-articular pro-inflammatory cytokine concentration and facilitates the movement of COMP from the joint space to the serum.