Osteoarthritis (OA) is the most common musculoskeletal disorder affecting a large population of all genders, races, and countries. Hence, this study aimed to determine the correlation between frequency of therapy sessions and quality of life using Western Ontario and McMaster Universities (WOMAC) index to grade the severity of knee OA using Transcutaneous Electrical Nerve Stimulation (TENS) and Ultrasound Diathermy (USD). This is a cross sectional study. Total 33 patients from purposive sampling with both unilateral and bilateral knee OA were recruited into this study. Patients were assigned into three groups based on Kellgren-Lawrence Radiological Staging System. All patients recieved 5 minutes of 3 MHz, 0.5 - 1.0 watt continuous USD, and 15 minutes of 80-100 Hz, 30-50 mAmp TENS for twice sessions a week or 8 times sessions a month. Patients were asked to answer each question of WOMAC index. Number of therapy sessions according to the patient's medical records. There was correlation between frequency of therapy sessions and WOMAC index to knee OA grade severity (p < 0.05). The greater severity of knee OA, the more therapy session of combination USD and TENS is needed. The higher WOMAC index, the lower quality of life of knee OA patients.