Repeated measures ANOVA showed that there was a highly significant interaction between acupuncture mode (verum vs. sham) and time (across all three treatment sessions) for rACC/MPFC Fisher Z values [F(2,27) = 13.403, p < 0.0001].
Due to the small sample size of each group (10 patients), we decided to combine the two verum acupuncture groups (low and high dose groups) because (1) the total treatment time, needle stimulation time, and reported sensations were the same in both verum groups; (2) we found no clinical outcome differences between the two verum acupuncture groups and both verum acupuncture groups showed a trend towards improvement when compared to sham treatment, and (3) high and low dose acupuncture needle stimulations evoked similar activation patterns (Additional file 3 : Figure S3) ; ( 4) reported sensations as measured by MASS were similar in both real acupuncture treatment groups, and both showed significant differences from the sham acupuncture group; (5) acupuncture prescription for Knee OA varies across different studies; combining two protocols may better represent clinical acupuncture in practice; and (6) combining two groups gave us more power to test our hypothesis.