In this study, we planned to investigate the effects of pulse electromagnetic field (PEMF) on pain relief and functional capacity of patients with knee osteoarthritis (OA). Fifty-five patients with knee OA were included in a randomized, placebo-controlled study. At the end of the therapy, there was statistically significant improvement in pain scores in both groups (P < 0.05). However, no significant difference was observed within the groups (P > 0.05). We observed statistically significant improvement in some of the subgroups of Lequesne index. These are morning stiffness and activities of daily living activities compared to placebo group. However, we could not observe statistically significant differences in total of the scale between two groups (P > 0.05). Applying between-group analysis, we were unable to demonstrate a beneficial symptomatic effect of PEMF in the treatment of knee OA in all patients. Further studies using different types of magnetic devices, treatment protocols and patient populations are warranted to confirm the general efficacy of PEMF therapy in OA and other conditions.