Effect of transcutaneous electrical nerve stimulation (TENS) on knee pain and physical function in patients with symptomatic knee osteoarthritis: the ETRELKA randomized clinical trial. - Reichenbach S; Jüni P; Hincapié CA; Schneider C; Meli DN; Schürch R; Streit S; Lucas C; Mebes C; Rutjes AWS; da Costa BR (Osteoarthritis and cartilage, 2022)