en آسیب شناسی ورزشی و حرکات اصلاحی Sport injury and corrective exercises پژوهشي Research <div style="text-align: justify;"><strong>Purpose:</strong> This study aimed to investigate the electromyographic activities and balance of Vastus Medialis Obliquus (VMO) and Vastus Lateralis (VL) muscles during Straight Leg Raise (SLR) in individuals with and without Patellofemoral Pain Syndrome (PFPS).<br> <strong>Methods:</strong> Through an analytical case-control study, 26 persons with PFPS and 26 healthy subjects were recruited by non-random and convenience sampling method. All subjects performed SLR movement. The EMG activity of VMO, VL and VMO/VL ratio were recorded and measured. The muscles activation level were compared between the 2 groups using the Independent t test. The obtained data were analyzed using SPSS.&nbsp;<br> <strong>Results: </strong>The mean and maximum EMG activity of VMO, VL and VMO/VL ratio did not have any significant differences between the PFPS and healthy groups (P>0.05). In other words, during SLR, the VMO and VL muscles activation in the PFPS group were approximately the same as the healthy group.&nbsp;<br> <strong>Conclusion:</strong> These data suggest that not all individuals with PFPS had weak quadriceps muscles. Many factors may contribute to PFPS that should be considered in the assessment and rehabilitation of individuals with PFPS.</div> Vastus Medialis Obliquus, Vastus Lateralis, Straight Leg Raise, Patellafemoral Pain Syndrome, Electromyography 197 204 http://ptj.uswr.ac.ir/browse.php?a_code=A-10-23-12&slc_lang=en&sid=1 Hiva Lotfi هیوا لطفی hivalotfi20@gmail.com 0000-0002-0763-4677 No Department of Physiotherapy, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran. دانشجو Afsun Nodehi Moghadam افسون نودهی مقدم afsoonnodehi@gmail.com 0000-0001-5843-2330 Yes Department of Physiotherapy, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran. دانشیار گروه فیزیوتراپی Mohsen Shati محسن شتی Mohsen.shati@gmail.com No Department of Ageing, University of Social Welfare and Rehabilitation Sciences, Tehran, Iran. استادیار گروه سالمندی دانشگاه بهزیستی