en Sports and Exercise Medicine Sports and Exercise Medicine Original Research Original Research <p> <strong> Background: </strong>Osteoarthritis is a disabling musculoskeletal disease with no definite treatment. This study compared the effect of Platelet-rich plasma (PRP) and Transcutaneous Electrical Nerve Stimulation (TENS) plus exercise in the treatment of patients with knee joint osteoarthritis. </p><p> <strong> Methods </strong>: 54 eligible patients with knee osteoarthritis were randomly allocated into two groups. (IRCT2012110611382N) Group A (27 patients) received 2 injections of PRP (4 weeks apart) and group B (27 patients) received 10 sessions of TENS as well as exercise during the study period. </p><p>  Clinical outcome was evaluated using the Knee injury and Osteoarthritis Outcome Scores (KOOS) questionnaire before the treatment, 4 weeks, and 8 weeks after that the treatment. Pain was also assessed using a visual analog scale (VAS). Time to an intolerable knee pain during treadmill workout was also evaluated using an objective test. </p><p> <strong> Results </strong>: In the PRP group, the mean KOOS symptom score improved significantly from baseline to the end of study, while the change was not significant over this period for the group B. In both groups, significant reductions were observed in VAS scores from baseline till the end of study. The mean time to feel intolerable knee pain during treadmill work out of PRP group increased significantly from baseline to week 4, but no significant changes were found in this parameter over the time of study in the group B. </p><p> <strong> Conclusion </strong>: Intraarticular injection of PRP is an effective, safe method for short-term treatment of patients with knee joint osteoarthritis. </p> Platelet - rich Plasma, PRP, Knee Osteoarthritis, Exercise. 513 521 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-1-847&slc_lang=en&sid=1 Hooman Angoorani hoomanangoorani@yahoo.com 200319475328460016924 200319475328460016924 No Department of Sports and Exercise Medicine, HazratRasool-e-Akram hospital, Iran University of Medical Sciences, Tehran, Iran. Ali Mazaherinezhad mazaherinezhad@gmail.com 200319475328460016925 200319475328460016925 Yes Minimally Invasive Surgery Research Center, Iran University of Medical Sciences, Tehran, Iran. Omid Marjomaki marjomaki@gmail.com 200319475328460016926 200319475328460016926 No HazratRasool-e-Akram hospital, Iran University of Medical Sciences, Tehran, Iran. Shima Younespour shima.younespour@gmail.com 200319475328460016927 200319475328460016927 No Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.