Chen, Li, et al. “Effects of Pulsed Electromagnetic Field Therapy on Pain, Stiffness and Physical Function in Patients With Knee Osteoarthritis: A Systematic Review and Meta-Analysis of Randomized Controlled Trials”. Journal of Rehabilitation Medicine, vol. 51, no. 11, Oct. 2019, pp. 821-7, doi:10.2340/16501977-2613.