Abstract Osteoarthritis (OA) is the world leading cause of chronic disability and pain in elderly. Among different types of OA, knee OA is the most prevalent condition as a result of aging and obesity. The aim of this study is to determine the relationship between BMI and severity of pain among knee osteoarthritis patients from Yangon Specialty Hospital, Yangon, Myanmar. The study was carried out at the OPD of Physical Therapy Medicine and Rehabilitation Department from 500-bedded Yangon Specialty Hospital. 52 knee osteoarthritis patients who visited to OPD and who met the inclusion criteria were included in this study starting from October, 2017 to December,2017. Cross sectional descriptive study design was used. Nutritional status was assessed by using BMI and SGA form. Waist circumference was also measured for nutritional status as BMI alone cannot be used to measure obesity. VAS scale and Wong-Baker faces pain rating scale were used to measure the pain intensity of knee OA. Lequesne’s index was used to measure the severity of knee OA. Then, the collected data were analyzed by using the IBM SPSS software version 23. As OA cannot be cured with medications alone, we can give them nutrition intervention and help them how to eat healthy diet to reduce and maintain weight in the future. Mean age is 57.96±8.83 years, mean BMI is 27.53±3.54 kg/m2 and mean waist circumference is 36.15±5.39 inches. In this study, 46.2% of the participants which is nearly half of 100% were 45-55 years of age. Even though old age is one of the main risk factors for knee OA, middle-aged participants had knee OA in this study. In this study, 88.5% of the participants are female, thus female has more risks for knee OA than male. 80.8% of the participants have duration of onset of >1 year. BMI ³ 25 kg/m2 and waist circumference of >35 inches have higher risks for knee OA. According to the study, middle age and old age women with BMI ³ 25 kg/m2 and waist circumference of ≥88 cm have knee OA.