Heat therapy is frequently prescribed to patients with symptomatic knee osteoarthritis (OA). Deep hyperthermia via localized microwave diathermy is effective in several musculoskeletal painful conditions. However, the efficacy of superficial heating is controversial. Furthermore, no clinical trials have yet directly compared the effects of these treatment modalities in knee OA. Hence, the purpose of the present study is to compare the effects of deep and superficial hyperthermia, induced via microwave diathermy and hot packs, respectively, on pain and function in patients with symptomatic knee OA.