Fig. 3

a–h Pro-inflammatory mediator evolution after two cold applications in the synovial fluid of ice-treated knees (N = 16) compared to contralateral non-treated arthritic knees (N = 16) in knee bi-arthritic patients (phase II). Sixteen patients with knee bi-arthritis were then included (phase II). One knee was treated with ice according to the study protocol (N = 16). The contralateral knees were used as paired controls (N = 16—on the right part of the graphs). The synovial fluid was analyzed before and after treatment as previously described, on both knees for each patient. The results of synovial fluid analyses of all the ice-treated patients (phase I + II; N = 31) are also shown on the left part of the graphs, for comparison. Data are presented as means ± SEM. Wilcoxon-Mann-Whitney tests were performed. *p < 0.05, **p < 0.01, ***p < 0.001. H0: first evaluation (9 a.m., before the first cold application); H24: second evaluation (9 a.m., 24 h later, after the two cold applications); controls: contralateral non-treated arthritic knees. Missing values were due to the fact that some cytokines and mediators could not be detected—or with out-of-range values—in some synovial fluid samples before and/or after cold applications (IL-6: N = 3 in ice-treated phase I + phase II patients (1 at H0, 2 at both H0 and H24), N = 0 in ice-treated phase II and contralateral non-treated knees; IL-1β: N = 2 in ice-treated phase I + phase II patients (1 at H0, 1 at H24), N = 0 in ice-treated phase II and contralateral non-treated knees; TNF-α: N = 0; IL-17A: N = 0; VEGF: N = 0; NFkB-p65: N = 5 in ice-treated phase I + phase II patients (2 at H0, 3 at H24), N = 0 in ice-treated phase II, N = 4 in contralateral non-treated knees (2 at H0, 1 at H24, 1 at both H0 and H24); NFkB-p65P: N = 5 in ice-treated phase I + phase II patients (2 at H0, 3 at H24), N = 0 in ice-treated phase II, N = 4 in contralateral non-treated knees (2 at H0, 1 at H24, 1 at both H0 and H24); PG-E2: N = 5 in ice-treated phase I + phase II patients (2 at H0, 3 at H24), N = 0 in ice-treated phase II, N = 4 in contralateral non-treated knees (2 at H0, 1 at H24, 1 at both H0 and H24))