Effects of intensity of electroacupuncture on chronic pain in patients with knee osteoarthritis: a randomized controlled trial oleh Zheng-tao Lv, Lin-lin Shen, Bing Zhu, Zhao-qing Zhang, Chao-yang Ma, Guo-fu Huang, Jing Yin, Ling-ling Yu, Si-yi Yu, Ming-qiao Ding, Jing Li, Xiao-cui Yuan, Wei He, Xiang-hong Jing, Man Li